tA\

TIJDSCHRIFT

DER

NEDERLANDSCHE

DIERKUNDIGE VEREENIGING

T IJ D S C H R I F ï

DER

NËDERLANDSCHE

DIERKUNDIGE VEREENIGING

ONDER REDACTIE VAN

Prof. C. Ph. sluiter,

als Voorzitter der Vereeniging, '

Dr. J. C. C. LOMAN, Prof. J. F. VAN BEMMELEN en

Prof. J. E. W. IHLE.

Sde SEI^IE

X)EEIj XIV^JI

BOEKHANDEL EN DRUKKERIJ

VOORHKEK

E. J. B K I L L

LEIDEN — 1919.

liOKKDRUKKKRlJ VOOrheetl K. J. BRILL — LEIDEN.

INHOUD.

I. Wetenschappelijke Bijdragen.

("Verschenen ÜVIaart, 1919).

Blad/.

M. VAN Trtgt, A contribntion to the Physiology of tlio Fresh-water
Sponges (Spongillidae) i

II. Verslagen.

Verslag van de gewone huishovidelijke vergadering van 29 Juni 1918 . i

Verslag van de wetenschappelijke vergadering van 28 September "1918. viir

Verslag van de wetenschappelijke vergadering van 30 November 1918. xii

Naamlijst der leden op 1 .lanuari 1919 xx

A CONTRIBUTION TO THE PHYSIOLOGY OF
THE FRESH-WATER SPONGES (SPONGILLIDAE)

BY
H. VAN TRIGT.

With plate l— VI.

PREFACE.

A paper as foUovvs must necessarily be established by a de-
tailed statement of observations as well as by illiistrations taken
from life. As my investigations have led to so many subjects,
this paper has become rather extensive ; and it would have lost
its clear survey, had I not taken special precautions to prevent this.

1. For a survey of the questions and the results, I refer to the
various points of the Introduction and to the adjoined points in
the Summary at the end of this paper. This Summary gives the
chief results, and the pages of the text, the tables and illustrations
concerning them.

2. In the text itself the questions and results are al ways printed
in italics.

My principal results have already been published in the Pro-
ceedings of the Kon. Akademie van Wetenschappen at Amsterdam,
meeting 24 Nov. 1917.

CONTENTS.

page

INTRODUCTION 3

METHODS • 8

RESEARCH 15

A. Tuk chlorophyll of the fresh-water sponges 15

I. How and wbere the green colouring-matter occurs ... 15

II. The 'behaviour of the green colouring-matter 17

III. The nature and structure of the green chlorophyll cor-
puscles 21

IV. The genus of the «symbiotic" alga; its mode of reproduction. 29
V. Green and colourless fresh-water sponges; under what cir-

cumstances they occur; the nature of their «symbiotie"
algae 35

VI. The structure of the colourless »symbiotic" algae ; how they

arise from the green ones 36

VII. The intrinsic amount of the various green and colourless

stages of the »symbiotic" algae in sponges. The factors

ruling this amount. How green and colourless sponges keep

up their wcolour", and how they arise from each other . 46

VIII. The nature of the wsymbiotic" association of sponge and

green alga; its use to the alga and to the sponge. ... 76

IX. Some other algae occuri-ing in tissues of Ephydatia . . . 116

B. Thk current of watkr in the canal-system of the fresh-
water SPONGE.S 118

C. The ingestion of food in the fresh-water sponges 138

D. The digestion in the fresh-water sponges 157

E. The defecation and excretion in the fresh-water sponges . 158

F. Appendix. Some separate observations 171

SUMMARY 176

BIBLIOGRAPHY 186

TABLES 1—15 189

ILLUSTRATIONS 217

Explanation of plates 217

Pi.ates. I— VI; Figs. 1—77.

INTRODUCTION.

If I venture to treat liere at large, witli the help of my
own research, the problem of the chlorophyll, of the current of
water, of the ingestion and the defecation in fresh-water sponges,
it is not, because there is but little known about these problems.
On the contrary ; investigators have already studied them since
decennaries. We even possess a great number of papers on these
subjects; some of which are considered in literature as standard
researches giving decisive results. Nevertheless, I think it neces-
sary to treat those problems once more; in the first place, be-
cause during my investigations, which I have continued as exact
as possible for at least 4 years, several of these results obtained
and generally acknowledged — some of them being of the greatest
interest — proved to me absolutely inexact ; and in the second
place, because I will be able to confirm by new and better proofs
some of the results, which have not yet been generally acknow-
ledged in consequence of a less complete argumentation.

I will mention in short the chief points (see also van Trigt, 57b) :
1. In 1882 Brandt (8, 9) came to the conclusion, that the
chlorophyll corpuscles of the fresh-water sponges were unicel-
lular algae (Zoochlorellae), morphologically and physiologically
independent of their hosts. Ray Lankester (35) and Geddes (22),
however, got to quite the opposite view : the chlorophyll corpuscles
of Spongilla are identical to those of the plants, the investigators
who think them to be parasitic algae are misled. Brandt's proofs
are good enough, but not yet quite sufficiënt ; he did not succeed
in convincing Lankester and Geddes. Nevertheless, Brandt's

opinion is almost generally acknowledged — eg. by Beijerinck (4)
1890, Delage (16) 1899, IIertwig (29) 1903, Oltmanns (47)
1905, Weltner (68) 1907 and Biedermann (6) 1911 — ; Sollas (53)
1906 only — and apparently Minchin (45) 1900 too — holds
the view of Lankester, though in a note he indicates the pos-
sibility of the chlorophyll corpuscles being algae. I will show by
decisive proofs that Brandt was right (see Summary, point 1 — 5).

2. The investigators, who agree with Brandt, unanimously de-
clare that the symbiotic alga of the Spongillidae belongs to the
genus Chlorella — eg. Beijerinck (1. c.), Oltmanns (l.c), Schenck
(56) 1908, Wille (69) 1911 — . But having examined the mode
of reproduction of those algae, I have been able to state 'that, at
least in my sponges, we do not meet with a member of the genus
Chlorella at all, but with a forni probably closely related to the
genus Pleurococcus (see Summary, point 6).

3. By lack of sufficiënt daylight green fresh-water sponges
become colourless, viz. creamy-white, and colourless sponges
remain colourless. In such sponges Lankester (1. c.) found the
chlorophyll corpuscles, which used to be green, now colourless;
and he concludes, that these colourless forms may either pass
directly into (green) chlorophyll corpuscles by the action of sun-
light, or that during their development, by sunlight, in stead of
yielding the colourless forni they pass into the green type. In
the same way Brandt (1. c.) says, wlien speaking about these
colourless corpuscles: „eben so gut wie die Chlorophyllkörper von
höheren Pflanzen, können doch aber auch die Chlorophyllkörper
von Algen bei mangelhaftem Lichtzutritt blasser werden" ; and
elsewhere: „dass die Chlorophyllkörper der Zoochlorellen ihre
grüue Farbe im Dunkeln einbüssen, ist selbstversttindlich". So
both authors suppose conformity of the behaviour in darkness
of the chloroplasts of the higher plants and of the chlorophyll
corpuscles of the Spongillidae ; and so they explain the fact
mentioned above, viz. that in darkness green sponges grow colour-
less and colourless ones remain colourless, by analogy to the fact
known from the Angiospermae : that chlorophyll can not be pro-
duced in darkness. This, now, proved to me quite inexact. The

lack of light is really the cause of the green (colourless) sponges
becoming (remaining) colourless in darkness, but for quite a
different — much more complicate — roason than Brandt and
Lankester think of (see Summary, point 7 — 15).

4. The general conception (except of Lankester c. s.) of the
symbiotic relation of fresh-water sponge and alga is, as a relation
probably based on mutual use. So Spongilla is almost considered

'to be a „classic" example of symbiosis next to the Lichens.
We possess however but a few proofs, very little decisive, con-
cerning this mutual relation of host and guest (Brandt 8). Now,
with my experiments I have come to the conclusion that, instead
of a classic example of symbiosis in the sense of the mutualism
of the Lichens, the association of sponge and alga may be called
at best a transition of a process of nutrition (of the sponge) into
a still very imperfect symbiosis (see Summary, point 16 — 19).

These were the original points I intended to examine. But, as
is usually the case, when seeking we find by chance quite new
ways leading to other territories. So I found out a method, which
enabled me to observe wholly intact, normally living tissue
of sponges with oil-immersion for many hours, on several consecu-
tive days. In this way I got an insight into the following points :

5. As for the cause of the current of water in the canal-system
of the sponges, the research and theory of Vosmaer and Pekel-
haring (62) 1898 are almost generally acknowledged — eg. by
MiNCHiN (45) 1900, Biedermann (6) 1911, Babak (3) 1912 and
partly by Jordan (32) 1913 as well — : By the irregular strokes
(to and fro) of the flagella of the choanocytes the pressure of
the water on the inside of the wall of the flagellated chambers
is continually changing; one time it is positivo, next time nega-
tivo. In the first case the choanocytes acting as valves will pre-
vent the water from flowing out through the prosopyles. If, on
the contrary, the pressure is lessened, water can easily flow into
the chamber by these openings. The sponge will thus suck in
water through the incurrent canals, which flows out again by the
osculum. The current in the flagellated chambers is uot regularly,

continually streaming but irregularly whirling. This is, in
short, the theory of Vosmaer and Pekelharing. Now, I have
been able to establish in my living sponge-preparations that the
movement of the flagelia, as described here, is not the normal
one, but abnormal, and caused by exhaustion. The real move-
ment takes place, just as in the Flagellata, in a spiral- or undu-
lating line, while the current of water in the chambers is deci-
dedly regular and quick (see Summary, point 20).

6. In close relation to the problem of the water-current in
sponges is that of the ingestion of food — already a very old
matter of dispute. Here too we owe the last and principal re-
searches to Vosmaer and Pekelharing (1. c), by whom was shown
once more, that the flagellated chambers, c. q. the choanocytes,
would be the real „eating-organs" (Carter) of the sponge; al-
though both these investigators think it possible, that now and
then food-particles can be captured by cells lining the canals.
In literature this view is almost generally accepted — eg. by
Delage (16) 1899, Sollas (53) 1906, Biedermann (6) 1911 and
JoRDAN (32) 1913. MiNCHiN (45) 1900, however, thinks ') that
in the simplest forms of sponges indeed the collar-cells represent
the chief „eating-organs", but that in the higher organized
ones the function of ingestion may be usurped more and more
by cells in the parenchyma (amoebocytes or porocytes). Now, I
myself have observed in my living preparations, that in Spongilla
ingestion certainly takes place by the choanocytes, but that there exists
still another mode of ingestion — for larger bodies only — at the
exterior of the flagellated chambers at the entrance of the prosopyles.

It stands to reason, that the mode of capturing food by the
choanocytes was conceived in perfect agreement with the theory
of the water-current, as mentioned by Vosmaer and Pekel-
haring. So these investigators declare that the motion of the
flagelia, by the whirling movement of the water it produces in
the chambers, causes, that food particles arrive easily w i t h i n
the coUars of the choanocytes and thus come in contact with

1) Here Minchin folio ws Metschnikoff (44).

their protoplasin. Now, as I have been able to observe in my
living preparations quite another waj of movement of the flagella
and the water-current as being the normal one in the flagellated
chambers, the way in which the choanocytcs capture their food
was also bound to prove wholly different. The food-particles are
by no nieans captured within, but at the outside of the collars
or at the outside of the colhir-cells themselves; so exactly in the
same way as in the Choanotiagollata (cf. Doflein (17)). Already
JoKDAN (32) said: „Den Vorgang der „Phagocytose" durch die
Kragenzellcn mit demj enigen zu analogisieren, den wir bei den
Choanoflagellaten kennen lernten, ist sehr verlockend, aber das
vorliegende Beobachtungsmaterial reicht nicht hin, uns ein Recht
zu solchem Analogisieren zu geben". Cotte (12) 1902, namely,
seemed to have observed something as a capturing of food at
the outside of the collars, although he said the capturing within
the collars to be the chief manner of ingestion.

Quite separate from the problem of ingestion of solid food re-
mains Pütter's theory (48, 49) 1909, 1914, which says that
sponges do not feed so much with micro-organisms as with or-
ganic substances in solution, present in the water.

(See Summary, point 21 — 23).

7. Finally the problem of defecation and excretion ; up to now
it has been studied but little, and the few results we possess,
and which we owe amongst others to Masterman (42) 1894 and
Cotte (13) 1903, are only accepted in literature with reserve —
BuRiAN (10) 1910, JoRDAN (32) 1913 — . There are mentioned,
for instance, an expulsion of cells loaded with waste solids at
arbitrary points of the inner or outer surface of the sponge-body,
and a process of defecation by the choanocytes. Now, I have
been able to observe in my living preparations, that defecation
(and probably excretion at the same time) takes place on a large
scale by means of vacuoles. And that probably this process should
be considered partly in direct relation to the above (point 6)
mentioned second way of capturing (larger) particles. So we get
to know a — very necessary — quickly working system of
cleansing of the sponge (see Summary, point 24 — 25).

8

These are the chief points of my investigation. I want to de-
clare emphatically that for all my microscopic examinations I
used no other than liviug preparations. Observing them has
been an inexhaustible source of enjoyment to me, also beyond the
problems I was about ! This makes me think : Those zoologists,
who devote themselves exclusively to morphology, should con-
sider that, when studying biological problems, they generally
commence by depriving the organism to be examined of the
most interesting phenomenon, it ever may show — even the
most interesting phenomenon on earth ! — : Life.

METHODS.

The capturing of sponges. The sponges were coUected in the
lakes near Leyden (Brasemermeer). Both forms, Spongilla la-
custris and Ephydatia fluviatilis, are to be found there in great
quantities; of course, such an unlimited quantity of proof-material
is of the greatest importance for physiological investigations.
When loosened from their supporting layer — stone or wood —
the sponges were immediately cleaned from adhering parts of
mud etc, , and transported to the laboratory as quickly as
possible.

The condifions of life in their habitat as to light, purity of
the water etc, in connection with the peculiarities of the fresh-
water sponges, were studied by me in all seasons for several years.
So I got many data, concerning the sponges living under normal
conditions, on which I could test the exactness of the results
of my proofs.

The culture of the sponges. After many experiments the fol-
lowing arrangement of the aquaria has proved to be the best.
The glass aquaria (capacity 50 and 100 litres), and the other
vessels used for the experiments, were standing in an unwarmed
apartment of the laboratory (windows on S, W.), while daylight
was tempered by partly closing the shutters and the air refreshed

9

by an open wiïidow. The aquaria contained water froiii tin; con-
duit, which was continually flowing in; as I may conclude from
my experiments , the water was entirely renewed in this way
in 5 — 10 hours. Plants, nor any nutriment for the sponges were
ever added — pure, streaming water proved to be best. In the
aquaria the sponges were in (tempered) daylight, not too many
together, in their natural attitude lying on wire-gauze, 10 — 20
centimeters from the bottom and 15 — 20 centimeters from the
surface of the water; in this way they were safe from the in-
fluence of anything that might sink to the bottom. The aquaria
were cleaned once in 1 — 2 months. For culture of sponges in
darkness aquaria arranged in the same manner but surrounded
by perfectly light-tight wooden cases were used. The Spongillae
generally kept alive for 1 — 1'j., months, in the beginning they
often grew strongly ; the Ephydatiae, however, sometimes lived
even for 5 months, but they did not grow so quickly as Spon-
gillae. Sometimes sponges were cultivated separately in glass
vessels (capacity 3 or 5 litres), also containing conduit-water,
though not streaming; tliis water was renewed once a day.

The culture of the isolated cMorophytl corjMsdes. The cultures
were obtained in the followi^g way : A green sponge was rubbed
and pressed, the parts of the skeleton removed, and the remaining
dark green liquid mixed with some water. Then this liquid was
kept quiet for about an hour, during wliich time a thick green
mass settled at the bottom — formed, as appeared, by amoebocytes
and other sponge-cells and by detritus — while a still green
liquid remained. The latter almost exclusively contained the
isolated green chlorophyll corpuscles. Next this liquid was divided
into equal quantities over many little glass vessels; these vessels
were filled with the culture-media wanted to the same volume
(50 cM'), covered with glass plates, and placed either in (tem-
pered) daylight, or in complete darkness in the same room as
the aquaria. In the beginning the culture media were renewed
every 2 or 3 days (as long as there were processes of rotting
of sponge-rests), afterwards once in 1 or 2 months ; to which it
was of nuich use, that the chlorophyll corpuscles, once having

10

been isolated, used to settle down to the bottom in one day's
time , then forming, together with sponge-rests, a continuous
membrane rather firmly attached to the bottom.

The cultures of colourless clilorophyll corpuscles (from colour-
less sponges) were obtained in the same manner.

The culture-media were the following: 1. water from the con-
duit, 2. solution of inorganic food, 3. solution of organic food,
either diluted or concentrated, 4. liquid from a pressed sponge,
also diluted or concentrated.

The following solutions of inorganic food were used:
I. Solution of Oehlmann (from Doflein (17)).

999 Gr. water

0.2 „ MgSO^

0.4 „ Na H^ PO4

0.4 „ K N O3

II. Solution of Beijerinck (from Gerneck (23) ).

100 Gr. water
0.05 „ NH4NO.,
0.02 „ KH, PO4
0.02 „ MgSO^
0.01 „ Ca C\,
traces Fe SO4

And the following solutions of organic food :

I. Solution of Artari (2).

0.5 7o peptone (Witte)

1 „ glucose

0.3 „ KH, PO4

0.1 „ Mg SO4

0.1 „ CaClj

traces Fe.^, Cl^

II, The same, but containing 6°/^ glucose.

III. ■ Diluted solution of organic food ; obtained by mixing 50
cM"* of the solution of inorganics I and 3 drops of the
following solution of organics (of Zumstein, from Dof-
lein 1. c.) ;

11

100 Gr. water
10 „ peptone (Witte)
10 „ glucose

4 „ citric acid

0.4 „ MgSO^

1 „ Kil, PO,

1 , NH^m,
The liqiiid from a pressed sponge (for culture-medium) was
übtained in this way : The superfluous water was pressed out of
some green sponges ; then the sponges were rubbed and the re-
maining liquid was filtered through a cloth, in order to separate
it from the intact sponge-cells (but not from the chlorophyll cor-
puscles etc). It was my intention to obtain in tliis way a me-
dium (without the living sponge) for the chlorophyll corpuscles,
differing as little as possible as to composition and concentration
from that in the living sponge. When this medium had to be
renewed, I could not make use again of pressed juice of a green
sponge — for the chlorophyll corpuscles cannot be held, not even
by filtering paper — ; I then used the juice of a colourless
sponge.

In all these cultures appeared among a colourless, granular
ground-substance formed by sponge-rests, besides a great many
chlorophyll corpuscles, of course also some other organisms (algae,
protozoa, bacteria); so they were not pure cultures. To this fact
I owe many interesting data concerning the influence of such
organisms on a culture of my chlorophyll corpuscles.

Nevertheless, I have tried in several ways to get really pure
cultures ; but always in vain. In the first place in the way in-
dicated by Beijekinck (4) for algae in general, the so called ge-
latine-method. As I did not succeed in applying this method to
the chlorophyll corpuscles — as little as Beijekinck — I will only
mention it in short: Before little colonies of the green chloro-
phyll corpuscles could be detected, the gelatine was always en-
tirely liquefied. I tried to suppress the development of bacteria
and mould in the originally sterile, neutrally reacting gelatine
by adding citric acid or sugar to it and by infecting with traces

12

of a culture of clilorophyll corpuscles ; but I did not succeed. Next
I tried to piek up a single chlorophyll corpuscle from a drop of
water by means of Sciioüten's apparatus, in order to transport
it to the sterile gelatine. The apparatus, which proved good for
bacteria, was of no use to me: in water the corpuscle sticks to
the needie, but it immediately loosens when taken out; and my
efforts to get a more appropriate form of needle-point were un-
successful.

So I did not get a pure culture of the chlorophyll corpuscles of
the Spongillidae. But this was of no consequence to my research ;
the ordinary cultures procured all results I wanted.

Microscopic preparations. As I stated already in the Intro-
duction, I did not use any other than living preparations ; namely
in two forms :

1. Ravel preparations of a sponge tissue, or preparations of
chlorophyll corpuscles from a culture, made on a glass-slide with
a drop of the original liquid ; the coverglass surrounded by
vaseline in order to entirely separate the preparation from the
outer world.

2. Sponges grown on coverglass. These preparations, in which
I observed many important phenomena in sponge life, were made
in the following way : A branch of a Spongilla — Ephydatia is not
appropriate for the experiment because of its slow growth — is
cut at full length in two, and each half is divided again into short
pieces of 1 c.M. Each piece is then put on its long flat side on
a large coverglass into an aquarium. When kept quiet, these little
sponges will then soon attach themselves with this side (the wound
side) to their glass ; while a thin membrane of newly formed
sponge-tissue will even extend from each old sponge piece as a
centre over the coverglass (Fig. 3). ïhis membrane thickens ac-
cording as it is growing older. In a week's time we then possess
in this membrane a w h o 1 1 y intact, n o r m a 1 1 y living
sponge preparation, fit for microscopic examination even
with an o i 1 - i m m e r s i o n ! To that purpose we put the cover-
glass, the sponge at the underside, on glass feet into a glass vessel
fiUed with water, so, that the upperside of the coverglass remains

13

on the surface of the water and tlie wliole can be phiced on the
table of the microscope. If we renew the water now and then,
and if, after examination, we put the prcparation back into
tlie aquarium, we can observe this living- tissue under wliolly
normal conditions for many hours, on several consecutive days.

Microscopising . All my microscopic examinations were made in
an Engelmann case, with the help of Zeiss's eye-piece n°, 4
and a most excellent specimen of a Leitz '/,.^ oil-immersion. This
last lens gave even better results than the precieus apochromatic
system of Zei.ss (with compens. eye-pie?es).

The estimating of the nuinher of (•hlorophijll rorpusdes^ etc. in
a preparation. I often had to know — for the sake of mutual
comparison — the absolute number of, for instance, the various
green and colourless chlorophyll corpuscles in a same volume of
several sponges, or in a certain volume of several cultures. If
I had wished to count these corpuscles, it would have required
a suspension — adequate to counting as for exactness — of equal
volumes of sponge-tissue (or culture) in the same quantities of water;
otherwise the exact method of counting would have been worth-
less. But of course, we cannot obtain equal volumes of sponge-
tissue or culture, nor a really equal suspension ; while, also,
counting would have proved a very tiresome work.

I therefore always took, by means of pincers from a sponge
or with a pipette from a culture, quantities of the material as
equal as possible, and spread it out on a glassslide, while parts
of the skeleton were removed. Then the coverglass was pressed
in an always equally stroug way, the superfluous liquid sucked
up, and the coverglass surrounded by vaseline ; next I estimated
under oil-immersion the number of the various chlorophyll cor-
puscles present in the whole microscopic preparation, consequently,
present in an almost equal volume of each sponge or of each
culture. This method, always applied in the same manner, gave
rather good results, as Table n°. 4, 6, 8 show; besides, the dif-
ferences, I wanted to know, were generally considerable enough.
So this method of estimating was in all respects preferable to
counting, which would have led to an imaginary exactness only.

14

The degrees of numerousness, used for estimating, are the fol-
lowing (arranged according to the increasing number) :

I = chlorophyll corpuscles absent in the preparation.

II = „ „ very rare „ „ „ ; viz. 1—4.

III = „ „ rare „ „ „; in some fields 1,

IV = „ „ rather rare „ „ ,, .

V = „ „ here and there „ „ „ .

VI = some chlorophyll corpuscles present in the preparation.

VII = several „ „ w w v « 5 ^^ every field

VIII = somewhat more „ „ „ „ „ „. [± 3-

IX = rather numerous„ „ „ „ „ „ .

X = numerous „ ^ v v « v •

XI = very numerous „ „ „ „ „ „ .

XII = a mass of „ „ „ „ „ „ ; the fields fill-

ed up with them.

It goes without saying, that the limits between these different
degrees niay not be considered as having been strictly indicated.

In the same way were examined for many sponges: the num-
ber of oildrops — present in a preparation or in an amoebocyte
— , the number of globules of carbohydrate (coloured by I) —
present in an amoebocyte — , and the number of amoebocytes —
present in a preparation — ; here too the same degrees were used.

One should, however, not try to compare these numbers
(I — XII) mutually in the different groups (that of the chlorophyll
corpuscles, of the oildrops, of the globules of carbohydrate, and
that of the amoebocytes) too exactly. — Besides, there will never be
any reason to do so. — • So, for instance, one should not consider
a number of chlorophyll corpuscles in a preparation, indicated
by X, as being exactly the same as a number of amoebocytes
also indicated by X. These degrees of numerousness may only
be directly compared within each group; while for the groups
mutually this only counts in a very limited way. This is inevi-
table, when using the method of estimating the number: for
our estimation is involuntarily influenced by the extent of the
corpuscles tho number of which must be estimated, and by the

15

spaco in which they oocur, as woll as by their greatest number,
we know as normally occurring within that space. ]iut, as men-
tioned above, we will never have to compare nmtually direct
the numerousness in the different groups (that of the chloro-
phyll corpuscles, that of the oildrops, etc), but only the chan-
ges of number — i. e. the increase or decrease — in the
different groups mutually. That ean always be done, of course.

RESEARCH.

A. THE CHLOROPHYLL OF THE FRESH-WATER SPONGES.

I. HOW AND WHERE THE GREEN COLOURING-MATTER OCCURS.

Spongilla lacustris and Ephydatia fluviatilis — the only fresh-
water sponges I am going to treat in this paper — oocur in our
country in a green and in a colourless form ; between which,
however, exist many intermediate tints from emerald-green to
creamy-white. But a nowly caught specimen never shows any
of these colours purely ; for, in consequence of its growth in the
more or less dirtied water of our canals and lakes, the sponge
tissue is so overloaded with particles taken from the water,
that the colour may have taken a dirty-brownish tint. The green
sponges do not show this very clearly, but creamy-white speci-
mina are even never to be found : they are always gray-brown
in different variegations. I therefore think that all the different
colours of the fresh-water sponges mentioned in literature (eme-
rald-green, green, brown, yellow-brown , flesh-coloured , gray,
dirty-white, white) are simply to be reduced to the principal
colours (grass-)green and creamy-white with their intermediates,
while the others can be explained as having been caused by the
dirtied water, in which the sponges were living.

I conclude this from the following facts : 1. I collected my
sponges in a moor-lake, with pale brown coloured water, contain-

16

ing numerous brown particles, 2. Generally not the whole (green
or colourless) sponge had such a dirty tint — at least not Spon-
gilla. As one knows, this sponge grows on stones or wood as a
thin crust, from which long (10 — 20 c.M.) finger-shaped branches
proceed ; contrary to Ephydatia, which generally forms flat
cushions with but little elevations. Of course, the growth of Spon-
gilla chiefly takes place at the end of the branches, and is rather
quick. But then it is obvious that the tissue of such a region,
where the cells are rapidly dividing, can not possibly have the
same degree of dirtiness (by particles from the water) as an older
not growing region. And besides, in young tissue there are no
flagellated chambers ; so there the possibility of taking particles
from the water is, of course, considerably reduced. This proved
to be the case. In sunimer, whon Spongilla is growing quickly,
it generally shows brightly (not dirty) coloured tops, '/a — 'A ^•^•
long; which, however, in specimina from cleaner water contrasted
much less distinctly with the older tissue. 3. When such a sponge
(with bright coloured tops on dirty-brownish branches) was put
into an aquarium filled with water from the conduit, all the
diff'erence in colour between the tops and the older tissue had
disappeared within a few days; also this last tissue had got a
bright colour, whether it was green, creamy-white, or an inter-
mediate. ïliis tissue, originally loaded with brown particles, then
proved under immersion to contain almost none. 4. Something
the like can be said of Ephydatia.

So the tivo cJdef forms of Spongilla lacusfris and Ephydatia
fluviatilis are a grass-green (Fig. 1) and a colourless (creamy-white)
one (Fig. 2).

I am going to treat the green form first.

The sponge owes its green colour to numerous little green cor-
puscles preserit in its tissues, especicdly in amoeboid cells (Eig. 69),
which for shortness' sake I shall indicate with the common name
of amoebocytes. (As for the different cell-forms in the fresh-water
sponges, see Weltner (68) 1907). These amoebocytes crowded with
fJic f/rmtt corpuscles form the greater mqjority of the sponge cells,

17

spread all over tlio body in the parenchyma, so among the meso-
gloea (intercellular substancc, ground subst. ') ). (As for their great
importance in sponge life, see Weltner (1. c.) and Minx'iiin (45)
p. 57 — 60). The green colour grains are mostly lying free in
the protoplasm (of the amoebocytes), only seldoni in a vacuole.
In fig. 4 such an amoebocyte is represented in the form I so
often observed, when wholly isolated from the sponge-tissue and
attached to the coverglass in my living preparations of tissue.
It then seemed entirely „vacuolized". Ho wever, I don't think
these open spaces to be real vacuoles belonging to the cell. (See
Appendix, III).

Besides in these amoebocytes, the green corpuscles also occur
— but much less numerous — in the pinacocytes of the inner
and outer surface of the sponge body, in the choanocytes of the
flagellated chambers, and finally in the intercellular groundsubstance.

II. The BEHAVIOUR OF THE GREEN COLOURING-MATTER.

We no'W have to examine of what the green cotyuscles of the
sponge cells consist; in other words, we have to prove that the
material of which the corpuscles consist is morphologically and
physiologically identical to the chlorophyll, that we know from
the plants. Sorby (54), Lankester (35) and Brandt (8) have
already studied this problem. Sorby and Brandt compared the
spectra of solutions of the green sponge colour, obtained in dif-
ferent ways, with the corresponding solutions of vegetable chlo-
rophyll ; in this way the identity of the spectra was stated.
Lankester compared the structure ; and concluded, that the simi-
litude in form and structure proves the absolute identity of the
green corpuscles of the sponges to that of the plants.

As regards the phgsiological identity^ we don't possess any deci-
sive proofs at all ; though this only should give the decision ! In
the first place we have to show that the green corpuscles pro-
duce O^ when exposed to light, and in the second place, that in

1) For this, see Appendix, I.

18

light they also photosynthesise (produce carbohydrate or oil). This
having been established, we are justified in declaring — in
connection witli the points of similitude already known — that
the green colouring matter of the sponges is clilorophyll. I have
been able to procure both proofs.

1. In order to prove the production of 0.^ in light, I proceeded
in the folio wing way :

a. I cut tv^o equal pieces from a branch of a green "Spongilla,
and an equally large pieee from a colourless one. These
pieces were put separately — without having been taken out of
the water — into glass vcssels, filled with water from the con-
duit, uiider inverted funnels and tubes, etc. (see Table Ic). One
green piece and the colourless one were placed into bright day-
(evt. sun-)lig]it, the other green piece, however, on the same spot
in darkness. At first no gasbubbles were to be found anywhere
in the vessels ; but at the end of the experiment the green sponge
piece, exposed to light, showed numerous rather large bubbles,
as well at the outside as within its tissue, and the funnel con-
tained a lot of them. The green sponge in darkness and the
colourless one in light, on the contrary, didn't show any; except
a few bubbles inside and outside their funnels, evidently formed
by air from the water. I have repeated this experiment several
times, al way s with the same result (Table la, b) : only the green
sponge, when exposed to light, formed gas-bubbles, the green
sponge in darkness did not, nor did the colourless one in light.
The quantity of gas produced, however, was always too little for
a determination. Yet it is almost beyond doubt, that it has been O2 ').

b. WiLSON (70) and Muller (4()) stated the fact, that rubbed
sponge material can regenerate to new sponge globules, able to
develop themselves almost in the same way as the gemmulae of
the frosh-water sponges. Now, I put equal quantities of such
globules originating in one green Spongilla, into 12 little glass
vessels of the same capacity, filled with water and covered with

1) According to Brandt, Hoog stated already in 1840 the rising; of gasbubbles
from a Spongilla exposed to sunlight.

19

glass plates. One half of these vessels was exposcd to daylight,
the other kopt in darkness (at the same temperaturc). After a
week's time the sponge globules in all 6 vessels, which had been
exposed to light, appeared to be still intact, while those kept in
darkness proved to bc intact in 2 vessels bnly, but wholly de-
stroyed in the other 4. These observations make us thiiik of a
production of 0^ by the globules in light. This is the more evi-
dent, when we consider that entering of 0.^ from tlie air into
the vessels was almost completely prevented by their glass covering.

c. To Engelmann (18) we owe the bacteria-method, that enables
us to detect the production even of traces of 0.^. It is based, as
one knows, on the fact, that many bacteria are brought to vio-
lent motion by the mere presence of but traces of O.,, while in
lack of 0^ they get at rest. To prove this production of 0.^ by
the green corpuscles of the Spongillidao, I proceeded as follows:
On the surface of an algal-culture I found a membrane of moving
bacteria, from whicli I grafted a littlo on peptone-gelatine. So in
a few days I got a sufficiënt quantity of the bacteria. I then
ravelled a piece of green Spongilla on a glass slide, etc, etc. (see
Table 2). After the preparation had been kept in darkness for '/^
of an hour, the bacteria were accumulating and violently moving
round the air bubbles, but elsewhere they had almost got at rest.
This proved that here we had to do with bacteria sensitive to
O^, as we wanted. After another period of darkness of ^4 of
an hour, the movements round the air bubbles also almost had
stopped. When, next, the green sponge preparation was exposed
to light, we could observc under the microscope that, little by
littlo, the movements of the bacteria were resumed all over, till
the original intensity was reached. We might repeat this ex-
periment numerous times, always with the same result (see Table
2) : in darkness the movements stopped, in light they were
resumed. Accordingly, the preparation proved to contain many
amoebocytes crammed with green corpuscles, and numerous of.
those corpuscles isolated. So these last ones produced in light
the 0.^, necessary for the movements of the bacteria.

I made this experiment with several preparations, also from

20

Ephydatia and always with the same result. But now the contra-
experiment (Table 2) ! When I proceeded with a colourless sponge
in the same way as described for a green one, I found that,
after exposure to Hght, the movements were not resumed by the
bacteria. Accordingly, the preparation of the colourless sponge
proved to contain n o green corpiiscles at all , neither isolated
nor in amoebocytes. I repeated this experiment also several
times.

I think to have given in these experiments the decisive proof,
that the green corpiiscles of the SpongilUdae produce 0^ in light,
hut not so in darkness.

2. Now we have to show the photosynthesis (production of carbo-
hydrate or oil) of the green corpuscles in light '). In the first
place I should mention that in fact most corpuscles show one —
sometimes more — drops of oil, but never any carbohydrate
(pag. 25). To prove their production, I proceeded as follows (Table 3):
Preparations were made from a light-green Spongilla (grown in
twilight and afterwards kept for some time in darkness) in a
darkroom by candle-light. One half of them was immediately put
into complete darkness, while in the other ones the percent of the
isolated green corpuscles containing an oildrop was examined
(Table 3 c). This proved to be 42° j^. These preparations were
then exposed to tempered day-light. Now we see in the table
that in two days the percent rosé from 42 to 79, but that
in the preparations in darkness it remained 35. Then being ex-
posed to day-light for two days, the latter too showed a rising,
namely from 35°/o to 78°/^; while at the end a percent of
+ 90 was reached in all preparations. I could also observe that
the oildrops of the corpuscles, which had been exposed to the
light for a longer time (so in culture n". 396 a — d) were larger.
So it is clear^ that the green corpuscles of the SpongilUdae
photosynthesise oil in light^ hut not so in darkness. I have re-

1) It sccms Ihat Brandt (1- c.) has observed this for Spongilla; he at least men-
lions that the isolated corpuscles remaiued alive for weeks, „according to their pro-
ducing assimilates". But he doesn't give more about it; and where he should have
treated the phenomenon more rxtensivcly, he does not mention it at all.

21

poatod this experiment several times (Table 3 a. b.j; always witli
the same result.

It appearod to me, that the oildrops are formed much more
qiückly, when the green corpuscles are exposed to light after
having been kept — as a preparation — ■ for some weeks in
darkness: in that case the percent rosé in half an hour from
38 to 70. This short exposure to light seems to have extended
lts influence also to later on ; at least in darkness the percent
rosé up to 88, This is not inconceivablo. The oildrops, once
having been produced , seem to be used but very slowly by the
corpuscles — even in darkness — (Table 3 a, n". 163 ; 3 b n*^. 210).
These two cases are by no means the only ones ; I have sometimes
been able to state that most green corpuscles of a culture, after
a period of 6 months in darkness, still contained a drop of oil.

Finally I have been able to directly observe the forming of
an oildrop in a green corpuscle, which at first contained none
at all. The colour grain had not been kept in darkness; so the
forming did not proceed so quickly: the first appearance was
made after 3 hours of exposure to light, a real oildrop only to
be seen after 21 hours.

So we have proved the identity of the green colour mg -matter of
the Sponglllidae to the chlorophyll of the plants hg physiological
argnments. We may now speak of the chlorophyll, the chloro-
phyll corpuscles of these sponges.

III. TlIE NATURE AND STRUCTURE OF THE GREEN CHLOROPHYLL

CORPUSCLES.

As I stated in the Introduction, the results of Brandt (8, 9)
concerning the nature of the chlorophyll corpuscles of the fresh-
water sponges are quite different from those obtained by Kay
Lankester (35) and Geddes (21, 22). Brandt concluded that
these corpuscles were algae, Lankester and Gteddes however,
that they consisted of chlorophyll formed by the sponge itself
as an inherent part of its cells.

22

I am now going to treat in short tlie arguments of Brandt.
In the following points he givos the chief differences between
chlorophyll corpuscles and algae :

c h 1 o r o p h y 1 1 corpuscles
parts of cells
consisting of groundsubst. -|~

chlorophyll
never a nucleus present
no cellulose membrane
not able to live by themselves

algae
cells by themselves
consisting of chlorophyll -j- un-

coloured protoplasm.
always a nucleus present
generally a cellulose membrane
able to live by themselves

ïhen Brandt examines, which of these two series may be
applied to the chlorophyll of the Spongillidae (and of the other
chloropliyll containing animals). That is to say, he extensively
discusses the investigation of Hydra viridis, and for Spongilla
hc refers to the results obtained in Hydra; in his way however,
it remains somewhat doubtful what Brandt exactly stated for
Spongilla. For the corpuscles of Spongilla he especially de-
scribes : 1. Generally a through-shaped chloroplast and hyaline pro-
toplasm. 2. A nucleus, that could be recognized very distinctly
by means of haematoxylin or magdala. 3. A diameter of 1.5 — 3 [a.
4. After having been isolated from the sponge-cells, they re-
mained normal and alive for 3 — 4 weeks. 5. Sometimes they then
seemed to have multiplied (but this required closer examination).
G. Green corpuscles of Spongilla, added to a culture of unco-
loured specimina of Stentor coeruleus were ingested by these ,
but not digested nor ejected ; so it proved to be possible to graft
these corpuscles. i

I have some remarks on these points : 1. The nucleus. As said
beforo, Brandt discusses Spongilla very briefly only and for de-
tails he refers to the description of Hydra. In that description
is mentioned, that in all corpuscles (after having been stained
witli haematoxyline) one or two, sometimes more, violet, round
or somewhat irregular spots could be distinguished ; Brandt
declares them to be nuclei. They were solid corpuscles, but their

23

more detailed structuro could not be examined becauso of tlie
small dimensious. jSTow I can not deny tho pos.sibility of their
being really nuclei; but to mo it seems rather premature to
simply declare one, two or more, somewhat irregular spots to
be nuclei, on the mere account of being stained violet by hae-
matoxyline. One will agree with me, after having read my own
observations (pag. 25 — 26). 2. ïhe grafting. Brandt's words are :
„Die Stentoren nalimen die grünen Körper alsbald in grosser
Menge auf und stiessen sie weder aus, noch verdauten sie die-
selben. Sie blieben auch dann grün, als Hr. K. sie für mehrere
Stunden in reines Wasser setzte". I must remark that, if the
Stentores have not been observed for more than some hours, this
experiment does not sufficiently prove the possibility of grafting
the green chlorophyll corpuscles.

Next we get to Lankester's quite opposite view. The latter
says to be convinced (by his morphological investigations), that
in Spongilla the chlorophyll is present in corpuscles which are
entirely identical to those of the plants, and formed, just as these,
by the protoplasm of the cells in which they occur : 1. A nu-
cleus can never be shown. 2. AVhen the containing sponge cells
are destroyed the isolated chlorophyll corpuscles remain intact
(also in plants). 3. It then appears that some protoplasm adheres
to every corpuscle; a fact which can be explained in this way,
that, when the amoebocytes are destroyed, a lump of protoplasm
sticks to each chlorophyll corpuscle 5 accordingly, there is no
differentiation of a mass of protoplasm belonging to every chlo-
rophyll corpuscle to be seen in the intact amoebocyte. 4. It was
not possible to discover amylum (by means of I.) within the cor-
puscles, but it could bc done in other parts of the amoebocytes.
5. By lack of sunlight Spongilla remains colourless; it proves
that in the otherwise green cells there are then colourless grains,
which appear to be chlorophyll corpuscles in a somewhat abnor-
mal condition. Lankester thinks it impossible to consider these
colourless grains parasitic algae, ready to change into green ones
by the action of sunlight. (Finally Lankester critisizes Brandt's
conclusions, which criticism Brandt (9) treats in his turn.)

24

Also on some of these points I have a few remarks: 1. A nu-
eleus coiild never be found. But we should consider — Brandt
mentions it too — that Lankester never used Brandt's staining
metliod but always picro-carmine only. '2. No differentiation of
protoplasm belonging to each chlorophyll corpuscle could be seen
in the intact amoebocyte. That is absolutely inexact; to me the
contrary proved to be the case.

I am noiv going to show^ hy decisive jyroofs, that the chloro-
2)hgU corpuscles of the Spongillidae are real algae associated in
y^sgmhiosis^^ 'to the spo?ige^ just as Brandt declared. For that pur-
pose I will make use of two sets of proofs, one being morpho-
logical, the other physiological.

a. Morphological proofs; description of the structure
of the green chlorophyll corpuscles.

I am going to treat the living green corpuscles of Spongilla
only, as those of Ephydatia are quite the same.

1. Protoplasm and chloroplast. The shape of the corpuscles is round
or somewhat oval ; the diameter 1.7 — 3.8 ^ci, generally 2 — 3 |U. Under
oil-immersion we observe that in most corpuscles the green cliloro-
plast takes exactly one half of the body, the other half con-
sisting of uncoloured protoplasm (Fig. 5). The separating line
between chloroplast and protoplasm, wliich in oval bodies is always
situated along the longest axis, may be bent a little. But there
are also numerous corpuscles with differently shaped chloroplasts
(Fig. 12 — 16, 23 — 24, 30), generally taking more than one half
of the corpuscle; or even two chloroplasts in one corpuscle. The
mutual relation between these different forms will be discussed
afterwards. It is a matter of course that one same chlorophyll
corpuscle, seen from different sides, will show different aspects;
so Fig. 24 and 30 give an aspect of Fig. 13, and Fig. 23 an aspect
of Fig. 5 and 12 — 15. The protoplasm of tlie corpuscles appears to
be more or less hyaline, not completely homogeneous, but usually
containing some diffuse, darker spots (Fig. 5). The chloroplasts,
on the contrary, appear to be completely homogeneous ; their

25

colour is green. All this concerns the isolated chloropliyll cur-
puscles as well as those lying in amoebocytes.

2. Enclosures. Very often the protoplasm contains oiu;, sonie-
times more, rcfractive globules, 0.4 — 1 [y. in diameter, wliich appear
blue-green whcn the microscope is well adjusted (Fig. 5). Some-
times one can also find them within the chloroplast. These glo-
bules are not stained by I (in KI sol.); but by sudan III (in
alc. sol.) they become red, and gray-black by osniic acid. So tliey
are fat-globules, better: oil-drops '). No other enclosures were
ever to be found within the chloropliyll corpuscles (except, of
course, what is mentioned sub 3 and 4-); so no carbohydrates:
I (in KI sol.) caused only a diffuse brown-colouring of the
whole corpuscle, but nowhere any special colouring.

3. TJw nucleus and pyrenoide. As I have mentioned already,
the chloroplasts are entirely homogeneous ; a pyrenoid was never
to be found. But now the nucleus! If one stains chlorophyll
corpuscles, killed with formol-alcohol (1 p. form. 40 °l^ + 9 p. alc.
64 %) and which have lost their green colour, with methylene-
blue, one will often find in them one or more sharply outlined,
refractive, blue globules and sometimes a more diffuse blue spot.
The sharply outlined blue globules (Fig. 38, 39) are doubtless
the originally blue-green oildrops, still occurring in the unstained
matter as well. By their refraction they simply concentrate
the pale-blue light in the field of the microscope, in the same
way as drops of ceder-wood oil do in a solution of methylene-
blue in water. Perhaps the more diffuse blue spots might be
nuclei ; they are smaller than the preceding ones and are always
situated near the middle of the corpuscle (Fig. 40, 41). When
the same material is stained with haemateine-eosine (de Graaf),
the oil-drops remain uncoloured, viz. blue-green; but sometimes

1) In cousequence of the very small dimensions of those globules it may sometimes
be dilticnlt to detect their red or gray-black colour; when comparing them however
with normal (not stained) globules, the ditference is always distinclly marked out. For
comparing oue should also stain other fat-globules, for instance railk, with the same
substances; one will see then, that only the larger globules have a bright red or a
dark gray-black colour, but that the colouring of the globules, having the same dia-
meter as our oildrops, is just as weak.

26

a corpuscle may be found containing a dark violet-red spot in
the same situation as the spots coloured by methylene-blue. I
stained the material, killed with formol-alcohol, also with haema-
toxyline, just as Brandt did; then the oil-drops appeared to be
coloured somewhat violet — in this case not by concentration
of the light in the field of the microscope — , while sometimes
chlorophyll corpuscles were te be found containing a violet spot
in the same place, where it was in the other stainings. But
there were also specimina containing numerous spots, even irre-
gular violet lines (Fig. 42), The same result was obtained by
staining of the material (with haematoxyline) when killed with
Zenker's liquid.

These results prove, that it is not impossible that those more
diffuse, centrally situated, little spots are real nuclei. Against this
view, however, speaks the following : 1. these spots were but
seldom to be found in a corpuscle; 2. in other cases the cor-
puscle contained numerous of those spots and even irregular lines
with exactly the same (violet) colouring. One might rather think
them to be accidental colourings of arbitrary enclosures of the
protoplasm (conf. the oildrops). Consequently, I do not venture
to settle the question of the prosence of a nucleus in the chloro-
phyll corpuscles.

When now we compare my results with those of Brandt,
there is very much conformity in the facts stated ; and only a
difference on the chief point of the frequency with which the
so called nuclei occur. Brandt found them in all corpuscles.
Now I supposo that Brandt, who ncver mentions the oildrops
in the corpuscles, evidently does not know them, simply has
always considered these also somewhat violet coloured oildrops^ as
nuclei, as well as the diffuse spots. In this way it is possible
that he found all corpuscles containing a nucleus.

4. The cell-ivall. Only one decisive way exists for demonstrating
a coll-wall: by means of plasmolysis. I therefore pvit the isolated
green corpuscles for many hours into a solution, which I had acci-
dentally at hand, viz. that of pag. 10, I (inorg., in concentration X
50). The plasmolysis could be observed very distinctly on many

27

spccimina; the cell-wall appearod as a very thin line without any
perceptible thickness (Fig. 6 — ^11).

Herewith the description of the structure is finished. We have
stated that the green chlorophyll corpusdes of SpongiUa are round
or oval hodies^ 1.7 — 3.8 (j. in diameter.^ surrounded hij a cell-wall,
and consisting of prof.oplasm and a chloroplast ; while perhaps a
nucleus is present^ hut a pyrenoide is absent. They inclose oildro/js,
hut carhohydrates ivere never to he found within them. From
these data we may conclude that, very likely, these chlorophyll
corpuscles are vegetahle cells.

The structure of the green chlorophyll corpuscles of Ephydatia
completely agrees with that of tlie corpuscles of Spongilla. So they
too are vegetahle cells.

h. Phy siological proofs.

1. The green chlorophyll corpuscles of Spongilla as well as those
of Ephydatia, isolated from the sponge tissues, can reniain normcd
and alive foi\ 6 months, and even longer. They were isolated and
cultivated in the way mentioned above on pag. 9 — 11. I am
not going to treat these cultures here, but I refer to the
extensive culture-tables (Table 4) at the end of this paper.

We know that, on the contrary, chlorophyll corpuscles isolated
from plant-cells are not able to live on ; as for instance they
swell and are destroyed, when put into water (see Brandt (8),
HuGo DE Vries (63), Jost (33) Kny (34), etc).

2. The isolated gre.en corpuscles of both sponge types multijdy
rather strongly in cultures, especially during the first 2 months;
but stages of division are also to be found in cultures of 6
months, even in those of 9 months (Table 4, 9, 10). I shall treat
these stages af ter war ds.

3. Green chlorophyll corpuscles, as we know them from the
sponge tissues, (dso occur free in )iature — viz. in the waters
in which the sponges are living — so, not inclosed by other
organisms, but quite independant. I found their number changing
from at least 200 per litre in the beginning of March up to at

28

least 3700 at the end of July. Also stages of divisiou occui' /Vee,
quite identical to those of the corpuscles of the sponges (Table 10).
The diameter of the single corpuscles may sometiines be somewhat
smaller than that of those in the sponges, viz. 1.4 — 3/y. ; the oval
shaped body may be lengthened. One may find the same forms,
however, in old cultures of the isolated corpuscles of sponges
too. Finally I will mention the fact that, free in nature, the cor-
puscles often stick together in masses of 10 — 120 specimina. I will
return to this subject later on.

4. Wheri the sponge dies ifs green corpuscles survive.

5. It proved p)0ssihle to me to durahly transmute colourless
Spongillidae into the green form, hy infecting them with green
corpuscles isolated from a green sponge. Lateron I will treat the
method, in which this infection is brought about, more extensively
(Table 7). Now I will mention only, that for that purpose the
colourless sponges were placed for 3 — 72 hours into a diluted
suspension of isolated green corpuscles in water ; after that
they were transported, either colourless or already light-green,
into an aquarium filled with water from the conduit only and
placed into day-light. The green colouring then proved, in the
course of some weeks, not decreased at all ; on the contrary, it was
strongly increased ; many sponges had obtained rather a normally
green colour in a month's time (see Table 8 W 103, 207, 246,
248, 254, 257, 258, 326, 327), and their amoebocytes proved to
be normally laden with normal green chlorophyll corpuscles (pag.
16 — 17). At the same time such colourless sponges, but without
having been in a suspension of chlorophyll corpuscles, were — as
a contra-experiment — also exposed to daylight in water from
the conduit. These sponges got a faint green tint (colourless
sponges always grow green in daylight; I will treat this after-
wards), but in intensity their colour remained far behind that of
the infected specimina (Table 8 n° 102, 206, 259, 328); proof,
that the laftor really owed their normal green colour to the
infection with chlorophyll corpuscles, foliowed by the rapid mul-
tiplication of these corpuscles.

From these experime^üs we mag deduce^ that the green chlorophyll

29

corpusdes are oryanisms^ on the one hand vapahle of liohuj bij
fhemselves without the sponye hodi/ ; on the other hand of accommo-
dating themselves to the life within the sponge tissues^ irhen taken
from the siirrounding water hy the sponge.

This result together with that of our rnorj)hological investigation
justifies the conclusion: that the green chloropJiijll eorpusdes of
the Spongillidae are algae, associated to the sponge in „sgmhiosis^\

IV. The genus of the „symbiotic" alga ; its mode

OF REPRODUCTION.

As I have mentioned already in the Introduction, the symbiotic
alga of the fresh- water sponges is generally considered to belong
to the genus Chlorella — e.g. by Beijerinck (4) 1890, Oltmanns
(47) 1905, SciiENCK (56) 1908 and Wille (69) 1911 —. I am
going to discuss the investigation of Beljerinck. This investi-
gator says :

„Es dürfte nicht überflüssig sein, bevor wir weiter gehen, an
dieser Stelle einen Rückblick zu werfen auf die durch die Cul-
turversuche festgestellten Eigenschaften unserer Gattung Chlorella,
sowie auf die dazu gebrachten Arten:

Chlorella: Einzellige, grüne, zu den Pleurococcaceeen gehörige
Algen, mit kugeligen, ellipsoidischen oder abgeplatteten Zeilen
von 1 — 6 f4, Mittellinie, gewöhnlich mit nur einem Chromatophor
von der Gestalt einer Kugelsegmentschale; Pyrenoid undeutlicli
oder fehlend, lm Lichte entsteht unter Sauerstoffentwicklung aus
KohlensJiure Paramylum^ welches sich mit lod hraim fdrht. Zell-
kern meist einfach, bisweilen in Zweizahl, von wechselnder Grosse,
nur aus Chromatin bestehend. Die Vermehrung heriiht auf freier
Zellbildung durch successive Zireitheilung. Die Theilproducte kom-
men f rei durch Platzen der Wand der Mutterzelle ; sie können
schr verschieden sein in Grosse ('/.^ — 4 //.). Schwarmsporen fehlen
voUstiindig. In süssem und salzigem Wasser, wahrscheinlich auch
auf dem Lande."

Next Beijerinck describes the different species belonging to

30

this genus: 1. Chlorella vulgaris, 2. Chl. infusionum, 3. ^CJdorella
{Zoochlorella) parasitica Brandt ; Chlorophyll von Spongilla fluvia-
tilis, vielleicht identiscli mit Chl. infusionum und wahrscheinlich
wahrend des individuellen Lebens durch Spongilla von aussen
aufgenommen. Isolirungsversuche nicht gelungen". And at last:
4. „Chl. (Zoochlorella) conductrix Brandt ; Chlorophyll von Hydra,
Stentor, Paramaecium und wahrscheinlich von vielen anderen grü-
nen Thieren".

In the first place I should mention the fact, that in botanical
literature of modern times the Chlorellae are no longer reckoned
among the Pleurococcaceae, but that Chlorellae and Pleurococcaceae
are considered to be two entirely separated groups (see Oltmanns
(47) 1905, Wille (69) 1911, and this paper "pag. 33—34).

But when we compare the definition Beijerinck gives for Chlo-
rella, and consequently for the symbiotic alga of the Spongillidae
as well, with my observations concerning this alga, we are struck
by the fact, that Beijerinck mentions paramylum, coloured brown
by I, to be a product of the photosynthesis, while, on the con-
trary, I found oildrops and never any carbohydrate that could
be stained by I. A thing of much more importance, however, is
the entirely different mode of reproduction I stated.

71k' mode of reprodndion of the green algae of the SpongiUidae.
When studying the different forms of chloroplasts I immediately
observed, that in cells with doublé chloroplast both halves of
the latter were always symmetrically situated with respect to an
imaginary axis of the cell (Fig. 16, 17a). I also often found two
cells, each with a single chloroplast, which cells were connected
one with the other along a short distance of their wall, while
their chloroplasts were situated in the same way, now symme-
trically with regard to the common cell-wall (Fig. 22a). Conse-
quently, the last couple of cells seemed to be a stage of division
of the first cell with doublé chloroplast. This proved to be really
the case: once that my attention was drawn to this fact, I have
observed numerous different stages of division (Fig. 17 — 22). Some-
times I have also been able to follovv the division of au alga —

31

at least for a part (Fig. 17a-c, 22a-c). Tliis division always pro-
ceeded very slowly; hours, even days passed before one could
obscrve the slightest change in the division-stagc. And this does
not only count for specimina in ravel-preparations, bnt also
for those tliat remained in absolutely nornial conditions eithcr
within or without tlie tissues of a living sponge grown on cover-
glass. It also proved probable to me that the algae, with the
different shapes of the single chloroplast (Fig. 12 — 15) mentioned
above (pag. 24), are all transitory stages from the alga with the
primitive and most occurring shape (in which the chloroplast takes
exacjtly the one half of the body, Fig. 5) into forms with doublé
chloroplast (Fig. 16,' 17), so into stages of division.

Knowing this, we may compose the following cyclus of develop-
ment of tlio symbiotic algae of Spongilla; we place the primitive
and most occurring form at the beginning and at the end : Fig. 5,
12— IG, 17a— c, 18, 19, 20a— b, 21, 22a— c and Fig. 5 again.

All illustrations of the symbiotic algae have been made with
great care from living specimina, with oil-immersion and in Engel-
mann's case. All these stages were found in cultures of the isola-
ted algae as well as within the tissues of the sponges.

I have still got to mention a few points somewhat more at
large: 1. The stages of division were by no means always larger
than the single ones ; this is clear, for the single forms may greatly
diflfer one from the other as to their dimensions.

2. I call attention for the eccentric way, in which the sepa-
rating wall in a mother cell is formed (Fig. 17b — c, 18, 29c). As
one knows, the separating wall in algae, for instance in Spirogyra,
is formed by a regular, concentric growth out from the existing
cell-wall ; the ring, formed in this way, closes more and more
towards the middle of the cell, till at last it divides the cell
body in two parts. I saw this but once in the symbiotic algae
(Fig. 25). In all the other cases the forming took place by eccen-
tric growth out from one side of the mother-cell-wall, while
the separating wall penetrated more and more into the cell till
at last it reached the opposite side (of the mother-cell-wall). It
is a phenomenon comparable to the one stated by Treub (57a.)

32

on cell clivisions in seed-buds of Epipactis palustris. Probably in
direct relation to this eccentric manner of cell division are the
facts, tliat the separating wall is generally thicker at the base
than at the top, and that both halves, the chloroplast has already
divided into before, diverge more on the side wliere the separa-
ting wall will start (or started) than on the opposite side (Fig. 17a — c,
18, 29). In the one case of concentric division which I observed
these phenomena, accordingly, did not occur (Fig. 25).

3. I want to mention a phenomenon that is only to be seen
on very accurate observation. From the apical end of the sepa-
rating wall, when growing, a very thin line is extended to each
of both halves of the chloroplast (Fig. 26 — 29). These Unes are
thinner than the separating wall itself, and evidently move on
through the whole cell with the growth of this ' wall. In con-
nection with the facts in Spirogyra, one might be inclined to
consider these lines as threads of the nuclear spindle; which
spindle will then move from one side of the cell-wall to the
otlier, according as its forming of the separating wall proceeds;
therefore, something like Treub stated in Epipactis. But I can
not say this for certain, for I don't possess any observations as
to the nuclear division.

4. When studying these stages of the algae in division, one
should take care not to confound simple figures caused by the
diffraction of the light with real cell structures ; one is apt of
doing this on account of the very small dimensions of the chlo-
rophyll corpuscles. These figures, however, are easily to be re-
cognized, as they are always parallel to the cell-wall or outline
of chloroplast.

5. I could never detect any tracé of amembrane
surrounding — as if it we re a mother-cell-wall —
a stage of division as for instance Fig. 20, 22 and 27 show;
although I have always accurately examined.

The chlorophyll corpuscles in the amoebocytes are nearly al-
ways turning slowly; one time one can observe sucli an alga
from this side, next from that side; a thing of mucli importance
when studying stages of division. In this way the following

33

aspocts of one and tlie same dividing alga were observed : Fig.
29 a — (/. In a the alga is seen exactly at the least bent part of
the wall (= h seen froni aside); in h the alga is seen on the top
(= a on top); in c in a position between a and è; and in (/more or
less from below ( = a in slanting upward direction). This alga
with its surrounding amoebocyte has been observed for 1^ hour.

It is a matter of course that I observed a great many of those
stages of division, nuich more than have been drawn here; they
were all like these; I will only add Fig. 31.

Besides these double-stages, there also occur plural-stages of
division, but mucli less numerous (Fig, 32 — 34).

What I have mentioned here about the cell-division for the
chlorophyll corpuscles of Spongilla concerns also the symbiotic
algae of Ephydatia as well as the similar algae, which occur
free in nature.

As I stated above, free in nature these algae often occur
sticking together in groups of 10 — 120 specimina, sometimes sub-
dived in small groups of 4 specimina. Evidently we have to do
then with the result of 2 successive divisions of a single cell.
Moreover, one may sometimes find the algae of one group (of
10 — 120) in almost the same stage of development; so, probably,
all of them originating in one cell. Neither the smaller groups
of 4, nor the groups of 10 — 120 pieces are ever to be found
surrounded by a common membrane or wall. Nevertheless, the
(round) corpuscles often obstinately stick together, wlien we try
to separate them; so, apparently, they are kept together with
a kind of slimy substance.

So we have stated^ that the green symbiotic alga of the Spon-
gillidae multiplies hy simple^ vegetative division of the irhole
mother-cell (into tivo)^ the new separating wall sticking to the
mother-wall and^ consequentlg, also dividing the latter {into two).
So there exists here no cell-division ivithin^ and indepeyident of
the mother-cell-wall, therefore no ,,freie Zellbildiing'".

Thus the symbiotic alga does not at (dl answer the definition

given by Beijerinck for Chlorella; neither the definition given

for Chlorella in modern literature — Grinzesco (24) 1903; Olt-

3

34

MANNS (47) 1905; Wille (69) 1911 — : Chlorella possesses a hell-
or hall-shaped chloroplast and multiplies hy „freie Zellhildung''\
the daughter-cells surrounding themselves within the mother-cell
each with its own membrane arisen quite independently from the
mother-cell-wall. Consequently, they are lying free within this
old wall and get at liberty by its bursting or early dissolviiig.
So they are aplanospores ; zoospores and sexual reproduction are
absent. A nucleus is present. A pyrenoide may be absent. The
product of photosynthesis is starch, oil or glycogen.

On the contrary, the symbiotic alga answers exactly the defi-
nition given in literature — Gay (20) 1891; Artari (1) 1892;
Chodat (U) 1894; Oltmanns (47) 1905; Wille (69) 1911 —
for the Pleurococcaceae : The Pleurococcaceae possess a disc-shaped
chloroplast and nmltiply hy simple vegetative division of the ivhole
mother-cell {into two)] the new wall, forming a partition in the
mother-cell and sticking to the existing wall, divides this one
as well (into two). So they do not multiply by „freie Zellbil-
dung". Zoospores, aplanospores, and sexual reproduction are
absent. A nucleus is present; a pyrenoide may be absent (Pleu-
rococcus vulgaris). The wall is not so very thick, or thin (Pleu-
rococcus vuig.). A jellied envelope is present, but in the genus
Pleurococcus rather indistinct. The product of photosynthesis is
starch or oil (the latter in Pleurococcus vuig. and others). The
algae live in the air or in fresh-water. The diameter of Pleuro-
coccus vuig. is 3—7 [j..

Now, my descriptum of the symbiotic algae of the Spongillidae
I examined (pag. 24 — 27, 30 — 33) entirely corresponds with this
definition of a Pleurococcus (except that the nucleus has not yet
been sufficiently demonstrated in the symbiotic algae). I therefore
consider these algae to be a form closely related — if not identical —
to Pleurococcus vulgaris Naegeli. It is only in dimension that both
algae differ, the symbiotic one being 1.7 — 3.8 ^a, Pleurococcus
vuig. (according to Artari) ') 3 — 7 [/.. One might call the first
Pleurococcus parasiticus.

1) Artahi calls it Pleurococc. vuig. Menegh.

35

I sliould mcntion, however, that it mig-lit be possible, that our
fresh-water sponge will associate with quito different unicellular
algae in other countries, as I will point out afterwards (at the
end of chapt. VIII and chapt. IX).

V. Green and colourless fresh-water sponges; under wiiat

CIRCUMSTANCES THEY OCCUR ; THE NATURE OF TIIEIR
„STMBIOTIC" ALGAE.

"When we examine under what circumstances the fresh-water
sponges occur, we find that, generally speaking, the green sjjon-
ges grow on places exposed to hrigJit day-ligJit — for instance on
the wooden lining of the lake bank — ; the colourless sponges^
on the contrary, on places in darkness or in fwilight — for instance
under bridges and landing places of steamers — .

One might ask if the green and the colourless form could
not be two separate varieties of the sponge. This is not the case ;
for, as I will mention afterwards, gree^i sponges j^rove to grow
colourless in darkness and colourless ones jirove to grow green in
light (Table 8, p. 66), while moreover one may often find in nature
specimina partly green and partly colourless.

I analyzed on a large scale the number and nature of the
symbiotic algae in fresh-water sponges by means of ravel prepa-
rations (Table 6 A, C). In that table (column 1 and 3) we see:

1. In the green sponges in light as well as i?i the colourless ones
in darkness green as well as colourless chlorophyll corpuscles
(algae) occur.

2. In the green sponges the green corpuscles are much more
numerous than in the colourless ones.

3. In the green sponges the colourless corpuscles are somewhat
less numerous thau in the colourless ones.

4. In the green sponges the colourless corpuscles are much less
numerous than the green ones; in the colourless sponges theij
are jiist as numerous or still somewhat more numerous.

I am speaking here about colourless chlorophyll corpuscles, in
other words, about a colourless form of the symbiotic algae. This
requires further explanation.

36

As mentioned in the Introduction, Lankester (35) already has
found in colourless sponges the otherwise green amoebocytes now
overladen with colourless grains, which appeared to be chlorophyll
corpuscles in a somewhat abnormal condition, viz. irregular and
angular. Lankester concluded that there had to be some relation
between those two (green and colourless) forms.

I have examined this more exactly and it proved to be the
case. But I must not only declare that — contrary to Lankester's
observations ■ — the colourless chlorophyll corpuscles may be per-
fectly similar to the green ones as to their structure, but also
that their mutual relation is quite different from what Lankester
thought (Introduction pag. 4). On account of its great importance,
I will treat this question in a new chapter.

VI. The structure of the colourless „symbiotic" algae; how

THEY ARISE from THE GREEN ONES.

I will treat now only the pure structure of the colourless chloro-
pliyll corpuscles^ as we can observe it from the well preserved speci-
mina in which it is still clearly showing. This structure is per-
fectly similar to that of the green ones, as shown in the illustra-
tion (Fig. 35) ; the diameter is the same. The colourless corpuscles
may also contain an oildrop and generally occur free in theproto-
plasm of the amoebocytes, just as the green ones do.

WJiat then is the relation hetween these colourless symbiotic algae
and the green ofies? Did the former arise from the latter or the
latter from the former?

In relation to the facts, that green sponges occur in light and
colourless ones in darkness (p. 35); that green sponges grow
colourless in darkness and colourless ones grow green in light
(p. 35) ; and to the fact, that we know the same to be the case
for the higher plants, one might be inclined to conclude that all
these facts are based on one same j^henomenon, known for the higher
2)lants, viz. that chlorophyll can not be produced in darkness.
Lankester and Brandt (l.c), indeed, did explain these facts in this
way, as I mentioned in the Introduction (pag. 4). And also

37

Oltmanns (47) supposes tliat iii the colourless gemmules of the
fresh-water spoiiges the algae would be colourless for lack of light.

Bilt is it correct to suggest this analogy of algae to Jiigher plants ;
is it not possihle that the symhiotic algae do produce chlorophyll
in darJmess?

When comparing the amoimt of algae in green and colourless
sponges (p. 35, Table 6) ooe is inclined to declare, on account of
the presence of green algae in colourless sponges in darkness and
of colourless ones in green sponges in light, that evidently lack
of light can not be the cause of the algae being colourless. But
this conclusion would not be right ; for it is possible that it is
dark within the tissue of a green sponge in light — therefore
the colourless algae — ; and on the other hand we know, that a
sponge, c. q. a colourless one, is able to capture green chlorophyll
corpuscles from the surrounding water (pag. 27 — 28).

In order to decide whether the symbiotic algae can produce
chlorophyll in darkness or not, we have to cultivate them isolated
from the sponge tissues. So I did on a large scale (see Table 4 B,
cultures in water, except column 6), with the following rosults :
1. During the first two months a rather vigorous multiplication of
the green material took place, together with an inrease of the
number of green chlorophyll corpuscles (and not caused by a pro-
pagation of other algae). 2. Even in cultures of 4 months and
older such multiplication occurred, or green stages of division
were to be found. 3. In old cultures the normal green corpuscles
were still present in a great number. 4. On the contrary, the
colourless corpuscles (with structure) in general did not increase,
but even decreased in number ; in this way : the original number
disappeared rather quickly, lateron some new ones might arise,
but also these disappeared after some time.

So the fact known for higher plants, viz. that chlorophyll can not
be produced in darkness, proved not at all appliable to our sym-
biotic algae. On the contrary, these algae can produce chlorophyll
in darkness very ivell indeed.

It proved then to me to be a well-known fact in botanical
literature since Schimfer (51) 1885, that algae can produce chloro-

38

phyll in darkness (Heinricher (27) 1883, Etard and Bouilhac
(19) 1898; MatruchÓt and Molliard (43) 1900; Oltmanns (47)
1905). Moreover, the same is known about the seedlings of some
Gyranospermae, about ferns and mosses (Staiil (55) 1909).

So we have to find another explanation for the facts, men-
tioned above (p. 35), than the simple one given by Lankester
and Brandt (p. 36—37).

Consulting the botanica! literature I found, that in algae the
producing or not-producing of chlorophyll — in darkness and
even in light! — depends for a great deal on the nature of the
feeding-milieu (Beijerinck (4) 1890; Artari (2) 1902; Grint-
ZESCO (24) 1903; Radais (50) 1900). But a rule in general
appliable cannot be given for it, one kind of alga behaves in
this way, another in that way. By combining the results of
the investigators mentioned we may, for instance, distinguish the
following 3 types of algae :

A. Scenedesmus.

a. when cultivated in light.

1. in water + salts + N H^ N O3 without organic sub-
stances no growth takes place (Sc. acutus) or vigorous
growth of green algae (Sc. caudatus).

2. in water + salts -\- little organi* substances growth of
green algae takes place.

3. in rich organic feeding solution the algae become colourless.
h. when cultivated in darkness.

1. when glucose is present in the solution growth of green
algae takes place.

2. in rich organic feeding solution the algae will probably
also become colourless.

B. Chlorella vulgaris, Stichococcus bacillaris.
a. when cultivated in light.

1. in poor or in rich feeding solution growth of green
algae takes place.
h. when cultivated in darkness.

1. in poorer feeding solution (water + salts + K N O3 +
glucose) the algae become colourless.

39

2. in i'ich foediiig solutioii (water + salts + peptone + glu-
cose) vigorous growth of green algae takes place.
C. Chlorococcum infusionum froni the Lichen Xanthoria pa-
rietina.

a. b. wlien cultivated in liglit or in darkness and in all kinds
of feeding solutions the algae rcniain green.

Ho the algae proüe to hecome colourless under verij ((i/f'ereiU
conditions as to UgJd and food. Therefore we ougJit to exmnine,
if perhaps oiir symhiotic algae can lose their green colour and
2)((ss into the colourless form hg a combination of darkness (or
light) and a certain feeding miliea. And at the same time we
should examine, if the colourless form of the syinbiotic algae mag
in its turn pass into the green one hg a certain combination of
light (or darkness) and feeding milieu.

For the present I will .treat the first question. We have to
examine then, to which of the foUowing types of algae — the
only ones possible and partly hypothetical — our symbiotic
alga belongs :

A. when cultivated in darkness.
type I (Scenedesmus).

in poorer feeding solution the algae remain green.

in rich feeding solution the algae become colourless.
type II (Chlorella, Stichococcus).

in poorer feeding solution the algae become colourless.

in rich feeding solution the algae remain green.

type III (Chlorococcum from Xanthoria).

in poorer feeding solution ]

. _ „ _ , . / the algae remam green,

m rich leedmg solution )

type IV (hypothetical).

in poorer feeding solution 1 , , ,

. , „ ,. , ,. the algae become colourless.

in ricn teeding solution \

B. when cultivated in light.
type I (Scenedesmus).

in poorer feeding solution the algae remain green,
in rich feeding solution the algae become colourless.

40

type II (hypothetical).

in poorer feeding solution the algae become colourless.

in rich feeding solution the algae remain green,
type III (Chlorella, Stichococcus, Chlorococcum frora Xanthoria).

in poorer feeding solution

in rich feeding solution
type TV (hypothetical).

in poorer feeding solution

in rich feeding solution

the algae remain green.

the algae become colourless.

A poor or a rich feeding solution here always means a solution
poor or rich in organic feeding substances.

To decide to which type the green symbiotic alga of our
sponges belongs, it was isolated from the sponge tissues and cul-
tivated in light and in darkness in various feeding solutions. I
will not treat these cultures here at large ; one can find a de-
tailed description in Table 4 A, B.

The resul t we infer from these cultures is, among ethers, that
the symbiotic algae remain green and multiply by means of
green descendants under all circumstances. However, we had not
yet examined every imaginable combination of feeding in the in-
organic and organic feeding solutions used here; on the con-
trary, some chief combinations only. So it might be possible
still, that a fresh-water sponge offered exactly such a combina-
tion of food to its algae, that they did lose their green colour in
darkness or in light. So we had to study this possibility as well,
for which a feeding solution was required, differing as little as
possible as to composition and concentration from the one sur-
rounding the algae in the living sponge. I got this solution (the
so called diluted and concentrated liquid from a sponge) in the
way described on pag. 11. The result inferred from these cul-
tures is quite the same as that from the preceding cultures, as
Table 4 A, B shows:

1. The isolated green symhiotic algae of the Spotigillidae, whether
cultivated in light or in darkness in poor or in rich organic
feeding solutions, even in liquid pressed from a sponge, remain

41

normal (green, for instance) and alioe for months, and multiphj
hy normallij green descendatits.

2. In goneral the nuinber of isolated colourless symbiotic
algae (with structure) does not increase in these cultures, but
decreases ; they disappear from the culture.

So the green symbiotic algae of the sponges belong to type A,
B, III, to the same type as the symbiotic algae of Xanthoria.

Next J wanted to examine (pag. 39) if the colurless form of
the symbiotic algae may pass into the green one by a certain
combination of light (or darkness) and feeding milieu. I cultiva-
ted therefore the isolated colourless algae in light and in darkness
in the same feeding solutions, as the green ones were cultivated
in. I refer to Table 4 C, D. The result was :

The isolated colourless symhiotic algae of the Spongülidae (n.b.
those with structure), ivhether cultivated in ligJit or in darkness
in poor or in rich organic feeding solutions, even in liquidpressed
from a sponge, disappear from the culture after some time; they
never pass iiito the greeyi form.

We may now conclude : It is impossible, that the green sym-
biotic algae pass into the colourless ones, nor can the colourless
algae pass into the green ones, by the combined influence of darkness
or light and a certain feeding milieu — at least not in those cases,
which regard the condition of the sponge. This also proceeds from
the following facts:

As I stated above, green sponges generally occur in light and
colourless ones in darkness or twilight. In nature however — as
exception to the rule, but by no means very seldom — colourless
sponges also occur in light and — rather seldom — green ones in
twilight. Sometimes one may even find, close together, some green
and colourless sponges in bright daylight, or in twilight. It goes
without saying that — as in each of these two groups of sponges
(that in light and that in darkness) the algae live under the same
conditions as to light and food — one may not attribute the fact
of the majority of the algae being green or colourless in one case
or in the other to the combined influence of those two factors.

42

What indeed iiiai/ he the relation betiveen these green and colour-
less algae?

I refer agaiii to Tablu 4 A, B. There we see that, when the
green algae decrease in number, the eolourless ones increase (in
order to disappear after some time). ïherefore it is probable, that
the green ones can become eolourless.

Next we should consider that, as green sponges grow eolour-
less in darkness (pag. 35), which goes together with a cousi-
derable decrease in number of the green algae and a considerable
increase of eolourless ones, so, we might say, together with a
transition of green algae into eolourless ones, we are now able
to state, that this transition is not caused by the combined influence
of darkness and the feeding milieu in the sponge tissues but that
it must be closely related to the life of the sponge ; in other
words, we want a living sponge to perform this transition.

I am. going to prove^ that the green symbiotic algae of the fresh-
water sponges can only pass into the eolourless ones hy dying.

I. Analyzing the nature and number of the symbiotic algae in
green and eolourless Spongillidae (Table 6), one will find the
already mentioned (pag. 35) green and eolourless algae. But exa-
mining these eolourless algae more exactly, we see that there exist
3 different forms of them : 1. the eolourless ones with clearly
marked out internal structure (Fig. 35) mentioned on pag. 36 ;
this form is the least numerous ; 3. the eolourless algae, the internal
structure of which is only visible as a shade (Fig. 36); this form
is somewhat more numerous (1 and 2 together are the group of
the „eolourless ones with structure") ; 3. the eolourless ones, the
internal structure of which is no more visible at all, but which
appear internally either homogeneous (Fig. 37) or somewhat
granular, and wich are the most numerous of the 3 forms (the
group of the „eolourless ones without structure"). But closely
examining one can still detect a 4*1^ group , viz. of „vague
shades" of eolourless algae, in which there is of course neither
any internal structure to be seen. All these forms of symbiotic
algae generally occur — as mentioned for the green ones and

43

the coloiirless ones with structure (p. 17, :5(!) - frec; in the
protoplasni of the amoebocytes ; so tliey are not lying in vaeuoles.
Nevertheless, sometinies one may also find theni in food vacuoles
(Chapt. YIU).

It is very likely now, that the 3 hxst groups, the colourless
algae with shade of structure, th(! colourless ones without struc-
ture, and the vague shades of colourless ones, are only successive
stages of „solution" of tlie colourless ones with clearly marked
out structure; for this reason it would be rather evident, that
the latter are dying.

II. I have been able to prove by numerous experiments, tiiat
in fact the isolated green symbiotic algae can change in this way
only : first into colourless ones with clear structure, then into
colourless ones with shade of structure, next into colourless ones
without structure, then into vague shades of colourless algae, in
order to finally disappear. The green algae were killed
purposely in many of these experiments, for instance by
heating or more or less intense lighting. (Table 5, n". 68, 94,
95, 290 n, 290 p, 307 1, 308 1, 318, a. o.)

In this table also many cultures taken from Table 4 are recorded.
In them it is striking to notice, that through infection of mould,
common algae or diatoms the green symbiotic algae are changed
into colourless ones with structure, while the latter, passing via
the other colourless stages nrentioned above, will disappear from
the culture {W\ 84, 851, 113, 141, 188, 189, 190, 194, a. o.).
Bacteria, on the contrary, don't seem to do any harm to these
green algae at all (Table 4).

As, when purposely killing the isolated green algae, we get
a succession of quite the same stages of colourless algae which
we also meet in sponges, it is indeed very likely, that in the
latter too the colourless algae with structure arise in no other
way than by dying of the green ones, in order to pass also after
that into the various successive stages of „solution" — mentioned
above — to finally disappear entirely from the sponge tissues.
And the more so, because the same succession of stages can be
found in cultures infected by mould, common algae and diatoms.

44

III. On pag. 41, treating the cultures of isolated colourless
algae, we concluded that these algae (n.b. those with structure)
always disappeared from the cultures, and never passed into
the green ones. The same proves to bc the case (Table 4) for
the isolated colourless algae without structure. Which was already
self-evident.

We have proved now, that the green sponge algae may change
into the colourless ones by dying. We shall have proved incon-
testably, that the green symbiotic algae within the sponge tissues
become colourless exclusively by dying (in order to disap-
pear afterwards), only when we have shown that all colourless
algae present in these tissues are really dying. The following
are the proofs:

IV. The general rule given under III ; whilo, on the contrary,
the green algae remain alive for months.

Y. When a sponge dies, its colourless algae do not remain
intact — as the green ones (p. 28) — but they disappear.

VI. Colourless stages of division of symbiotic algae are but
seldom to be found in sponges — on the contrary several green
ones (Table 6) — ; therefore the former must probably be explained
as having been originally green.

VII. As known, living protoplasm is generally not stained,
or less quickly stained than dead one. By means of this fact I
could definitively decide whether the colourless algae were alive
or not. I therefore made ravel preparations of living, green and
colourless sponges, and added equal quantities of a solution of
eosine or methylene-blue in water, with the following results:

1. Green SpongiUa material containing numerous green symbiotic
algae, a few colourless ones with structure, and rather numerous
colourless ones without structure.

A. In eosine. After 25 hours the numerous green algae have
as a rule not been coloured red, only very seldom one meets
with a green specimen with red tint. Colourless algae are but
very seldom to be found, almost all of them are red : the few
with structure - they have n o green chloroplast ! — as well
as tlie rather numerous ones without structure.

45

B. In methylene-blue. After 25 minutes the numerous green

algae are not jet blue at all. Colourless algao, however, are no-

where to be found, all of tbem are blue : the few with structure

(they have no green chloroplast !) as well as the rather numerous

-ones without structure.

2. Colourless Spoyigilla material containing several green symbiotic
algae, a few colourless ones with structure and rather numerous
colourless ones without structure.

A. In eosine. After 25 hours the (several) green algae are not
yct red at all. Colourless algae are but seldom to be found, al-
most all of them are red: the few with structure (without green
chloroplast), as well as the rather numerous ones without structure.

B. In methylene-blue. After 35 minutes the (several) green
algae are not yet blue at all. Colourless algae, however, are
nowhere to be found, all of them are blue : the few with structure
(without green chloroplast) as well as the rather numerous ones
without structure.

The same counts for the algae of Ephydatia.

By these last experiments we have got the decisive proofs,
that all colourless symbiotic algae in sponges are dead, at least
are dying. So we have incontestahly sJioirn^ that the green „sgm-
hiotic^ algae in the tissues of the Spongillidae hecome colourless
exclusivelg hg dging (of the algae^ namelg), in order to graduallg
pass from colourless algae tvith clecir structure into the successive
stages of ^solution''\ colourless algae u-ith sluide of structure^ co-
lourless ones without structure^ vague shades of colourless ones, and
to fincdly disappear.

For completeness' sake I want to mention that the colourless
sponge algae, arisen from green ones in a culture infected by
diatoms (pag. 43), were also quickly stained with methylene-blue.
This proves that they too were dying.

46

VII. The intrinsic amoünt of the various green and

COLOURLESS STAGES OF THE „ SYMBIOTIC " ALGAE IN SPONGES.

TllE FACTORS RULING THIS AMOUNT. IIOW GREEN AND COLOURLESS

SPONGES KEEP UP THEIR „COLOUR", AND HOW THEY ARISE

FROM EACH OTHER.

a.

We now have stated the nature and origin of the colourless
symbiotic algae, and resumé the discussion started in chapter V.
We put the questions: What is a green sponge, what a colourless
one; how do they keep up their „colour", and how do they arise
from each other?

For the present we might answer the first two questions as
follows (pag. 35, Table 6) : Green sponges are sponges containing
a great number of living green algae and a smaller number of
dead colourless algae; colourless sponges are sponges containing
a small number of living green algae and a greater number of
dead colourless ones. But ive sJiould now compare the green
sponges — usually occurring in Ught, as we know (p. 35) — and
the colourless ones — usually occurriug in darkness — more
accurately as to their intrinsic amount of the various (green and
colourless) stages of the symbiotic algae; especially newly caught
sponges.

To that purpose I analyzed, as mentioned on p. 35, a great
number of those Spongillidae, green and colourless ones, Spongillae
as well as Ephydatiae (Table 6 A, C) ; the amount of algae in
Spongilla was examined separately in tissues in different stages
of development: in very young tissue, in full-grown, and in
tissue at rest (gemmulae). The number of the algae mentioned
always concerns the amount present within an equal volume of
each sponge. The results of the analyses are as follows:

1. Green as well as colourless symbiotic algae occur in the green
sponges in light as well as in tJie colourless ones in darkness.

2. in the course of the development of the tissues of tJie green
Spongillae the numher of the green algae ,remains constantly con-

47

siderable, decreasing a liftle in the gemmuh-stage. The niimher
of the green stages of divisioti is comparatively great^ hut in gem-
muJes theg are absent; hardlg the gemmules have germinated,
however, and the number increases again. The number of the coloiir-
less algae irith structure is small and remains rather constant
during development^ showing a considerable decrease diiring and
after the gemmule stage. The number of the colourless ones ivithout
structure is not great at the beginning, but increases rather con-
siderahhj afterwards, also showing a strong decrease (as far as
we mag judge) during or after the gemmule stage.

3. Li the course of the development of the tissues of colourless
Sponglllae the number of the green algae remains constantly smdll,
in order to disappear completely in the gemmule stage; ivhen,
however, the gemmules have germinated the number immediatelg
increases. The number of the green stages of division is constantly
very small; as a t'ule they are even missing. The number of the
colourless algae with structure is not great and remaijis rather
constant during development, showing a considerable decrease during
and after the gemmule stage. The numher of the colourless ones
tmthout structure is ratJier great at the beginning and increases
considerably afterwards, also showing a great decrease during and
after the gemmide stage.

4. In this way one observes in the tissues of the green Spon-
gillae as well as in those of the colourless ones a gradual change
of number of the various stages of algae: from very young tissue to
full-grown, from full-grown tissue to gemmules, and from gemmules
to very young tissue again.

5. During or immediatelg after the gemmule-stage the tissue of
a Spongilla contains a minimum of green and colourless algae.

6. ]n the green sponges the numher of the green algae is
usually much greater than that of the colourless ones (with, and
without structure) together ; only in some cases this number is equal.

7. In the colourless sponges the nutnber of the green algae is
always much smaller than that of the colourless ones together.

8. In the green sponges the green algae are always much more
tiumerous than in the colourless sponges.

48

9. In the green sponges the colourless algae are generally less
numerous than in the colourless sponges — of course one must com-
pare tissues in the saine stage of develop)ment — ; this concerns
the colourless algae ui'th structure as well as fhose u-ithout. For
the first ones this difference in numher is smaller than for the
last ones ; and for the latter it still increases rather considerably
during the development of the sponge tissue^ in order to prohahly
disappear almost entirely during or Immediately after the gem-
mule stage.

10. In the green and, in the colourless sponges the numher of
colourless algae with structure is ahvays much smidler than that
of those without structure.

11. The total numher of symhiotic algae present in the green
sponges surpasses that in the colourless ones.

Having stated this^ we want to know^ what is the reason of
all this {point 1—11). In short, why in nature a {green) sponge
in light contains an excess of green living algae and a smaller
numher of colourless dead ones, a (colourless) sponge in darkness,
on the contrary, an excess of colourless dead algae and a smaller
numher of green living ones ; how hoth sponge types keep up their
„colour'"; a?id how they arise from each other (pag. 35).

For that purpose we have to examine tJie factors ruling the
numher of the symhiotic algae in the sponge tissues. These factors
are 6 in number, viz. :

A. the import of the algae from the surrounding water into
the sponge (the factor of import).

B. the export of the algae from the sponge-tissues into the
surrounding water (the factor of export).

C. the increase of number of the algae in certain parts of the
tissues by the reduction or deatli of other parts (the factor
of reduction).

D. the dccreaso of number of the algae in a certain sponge-
volume by the growth of the sponge; (the factor of growth).

49

E. the niultiplication of the green algae within the tissues
(the factor of multiplication).

F. the mortality of the green algae within tlie tissues (the
factor of mortality).

I shall now treat each factor separately.

A. The factor of import.

As I mentioned above (pag. 28), it is possible to durably
transmute colourless sponges into the green form by placing
them into a diluted suspension of isolated green symbiotic algae
in water, I give a more detailed description in Table 7. There
we see, that a living colourless Spongilla (volume 3 — 10 c.M^)
is able to make perfectly clear within a few days 3 litres of a
grayish suspension of algae, by which the colourless Spongilla it-
self grows light-green; and that the rapidity of this process is
directly related to the number of oscular tubes, the sponge shows.
As we know from the research of Vosmaer and Pekelharing
(62), these tubes accelerate the rapidity of the water current
through the sponge body — serving as lengthening pieces of
the draught canals — . Therefore we may conclude that, the
quicker the current in the canals of the colourless sponge,
the more quickly the sponge will gei clear — so to say by
filtering — the troubled suspension, and itself will grow light-
green by capturing the green algae. The oscular tubes are not
indispensable, of course — as was proved — ; the current of
water can also go on, when they are lacking. One might think it
possible, that the sponge does not only catch the algae within
its tissues, they have got into by the current, but also at its outer
surface. This possibility might be realized; but it can hardly
come into consideration in comparison with the first method of
capturing, as I will point out afterwards in chapter B and C
(on the current of water and the ingestion of food). I will only
mention now that the algae are soon joined quite normally
within the sponge amoebocytes (not vacuoles!), and that the light-
green colour of the sponges, after they have been transported
into daylight into aquaria filled only with water from the con-

4

50

duit, does not at all decrease in tho course of' some weeks but
even strongly increases, as stated already on pag. 28. All this
concerns Spongilla as well as Ephydatia. (See Table 8.)

In this way the import of the green algae proved possible.
One might ask, however, if this factor really exists in nature
under normal conditions. This is certainly the case. For we
know that the symbiotic algae occur free in nature in exactly
the same waters as the sponge is living in (pag. 27 — 28); namely
to the amount of at least 200 por litre in March and at least
3700 in July ; but these nunibers give a minimum only, probably
very much too low. Moreover, one should not consider the in-
tensity, with wich a sponge filters the surrounding water clear,
to be but weak. As to this, we saw in Table 7 that a little
gponge (of but 3 c.M-' vol.) is able to raake clear 3 litres of a
troubled suspension within 3 days, while the filtered water was
again and again mixed with the suspension. So, how many times
had not the same water to pass through the sponge body before
all was clear at last; how many litres has the little sponge really
filtered in those 3 days! Another proof of this really enormous
„filtering power": sponges as large as a finger proved able to
make clear 3 litres of water mixed with 2 c.M'^ of milk within
a day's time; but exclusively when oscular tubes were present.
(This result was not caused by sponge-enzymes, as one might
think; for such liquids mixed with material from a pressed
sponge remained troubled for days. Nor did the milk sink to
the bottom).

Having stated noiv the -p^'^sence of green symbiotic algae free
in the water and the enormous yifiltering power'''' of a sponge^ we
mag conclnde that in nature the import is a vigorouslg and con-
tinualhj acting factor of increasi?ig the number of green algae in
sponge-tissues. And this must be the case ! For we stated (p. 47)
in colourless sponges from darkness that green algae are con-
stantly present in a small number, that stages of division are
generally absent, that the colourless algae (without structure) in-
crease considerably in number, in other words, that green algae
are continually dying; so it is absolutely necessary, that new

51

green algac are constantly imported froni the surrouiiding water
in order to keep up their (sniall) quantity witliin the sponge
tissue (the factor of reduction is normally not acting). Tli(;refore
the import is the only factor of increase of the nuniber of green
algae in colourless sponges in darkness.

When treating the factor of import I should mentioii aiiothcr
remarkable fact. In winter, wlien the sponge tissue is reduced
to tlie gemmules fixed quite free in the skeleton, several normal
green symbiotic algae provo to bc sticking to that skeleton ; pro-
bably caught there in the course of the winter from the flowing
water. The gemmules, now, when germinating on their place in
the old skeleton — which liappens very often — will immediately
find some green algae to their disposal. So the rapid increase
in number of the green algae in newly germinated gemmules, I
mentioned on p. 47 (3), has to be explained.

Next one might ask if in nature the factor of import does
only concern the green algae, or the colourless ones too. ïhe
latter would be realized, when also colourless algae occur free in
nature. This is certainly the case. Their number, however, always
proved to be but very small, compared to that of the green
ones; what stands to reason (conf. pag. 42- — 45). Therefore fhe
factor of inqmrt may be ?ieglected as far as the colourless alyae
are concerned.

Finally ive may accept that the factor of import is eqnally
active in (green) sponges in light as in (colourless) sponges in
darkness ] for the number of the algae in the surrounding water
will be equal for both of them in consequence of the continual
water circulation, and both sponges will probably possess the
same „filtering power" ').

1) From an experiment it seems to re&ult that the „filtering power" of green
sponges in light is greater than that of colourless sponges in darkness. In this case
also the import woukl be greater in the llrst sponges. We want, however, many ex-
periments to answer this question, and for the moment it is of no iraportance to us
(see the note at pag. 68). It will, however, be much more important when consiJered
in relation to a lack of O2, which possibly exists in (colourless) sponges in darkness
(chapt. VIII).

52

B. The. factor of export.

I treat this factor as theoretically possible and the reverse
of the import; for a sponge laden with algae might continually
eject some of them ; though the above stated eagerness with
which a sponge captures, algae does not make this supposition
very likely. But I should mention that I have really observed
sometimes (not often !) the ejecting of green symbiotic algae'
together with feces by vaciioles in the process of defecation, I
shall treat afterwards (chap. E). The export can not be expe-
rimentally stated in another way ; for a sponge in captivity may
always show some small parts of its tissues dying (at least this
possibility can never be excluded), whereby algae are set at liberty.
I thmk we may consider the export of algae from the sponge
tissues as an uncertam^ but prohahly not importa^it factor.

C. The factor of reduction.

After some time in captivity the fresh-water sponges show a
reduction of thcir tissues, which originally filled the whole ske-
leton but then begin to reduce to the inner parts. This may be
the consequence of a progressive dying of the outer layers, fol-
iowed by tlieir destruction. At least this is often the case. A
same phenomenon of reduction, however, might also be caused by
the tissues growing more and more compact, by the internal ca-
nals and lacunes being filled. It seemed to me that in a sponge
in reduction always both processes were going on. Their influence
on the remaining paj't of the tissues wonld he the same: the
numher of the algae present ivithin the unit of volume o f these tissues
ivoiild increase. When the reduction is caused by the tissue growing
more compact, this result is quite evident. In the other case we
may distinguish two possibilities: 1. The dying amoebocytes might
be (partly) ingested by the remaining ones, with preservation of
the green algae. 3. The destruction of the dead amoebocytes would
set numerous green algae at liberty in the neighbourhood of the
remaining sponge parts; thus the factor of import would be in-
creased. One can often observe this last phenomenon: a dying sponge
is surrounded by a green cover of algae, settled to the bottom.

53

lil nature, howcver, tlio process uf rcduction occurs in autumn
only. We iimij therefore neglect t/iis factor for sponrjes living
free in nature (except in antumn) ; but we should prev(;nt tliat
in our experiments (in aqiiaria etc.) this reduction bccomes effi-
ciënt, and we should take care to limit its troubling consequences
(the increase of the import) as miich as possible by a continual
vigorous circulation of fresh-water through the aquaria.

D. The factor of (jrowtlu

As a very young sponge forms but a rainute corpuscle, when
full-grown, however, a large ernst witli long branches (10 c.M.
and even longer) — Spongilla — or a thick cushion — Ephy-
datia — , it stands to reason that tlte groirt/i of tJie sponge imist
be (not in a short, Ixit in a long space of time) a verg aetive
factor of decreasing the nnmher of algae ptresent in the unit of
volume of its tissues.

One should consider, however, that growth takes place almost
exclusively at the top of the branches in Spongilla, as I men-
tioned already on pag. 16. So especially here the factor of
growth will act, although it might be possible that this in-
fluence is spread all over the sponge tissue by means of an ac-
cumulation of amoebocytes from all parts of the sponge body to
the branch tops. But it is remarkable to notice that these tops
are exactly the parts of a sponge, which become green first of
all and remain so for the longest time, as I stated repeatedly ;
so some other factors must act here as well. Nevertheless, I have
once found in a very warm season a great number of quickly
grown, green Spongillae with indeed very light-green coloured tops.

Green Spongillae (from light) proved to be larger than colour-
less ones (from darkness). This difference can not always be ob-
served, of course; nor is it always so prominently marked out as
in Fig. 1 and 2 ; but 1 have been able to state it in general and
in different months of several years. Later on I will treat the
cause of this phenomenon (chap. YIII). So tve mag conclude the
factor of growth to be more aetive in green sponges in light than
in colourless ones in clarhiess.

54

E. The factor of multipUcation.

We stated above (p. 27, 31, 47, and Table 4, 6) that the
green symbiotic algae multiply, when isolated in cultures, as well
as within the tissues of the sponge.

We have to examine now the rapidity of the multiplication
under different outer conditions (Table 9, 10). We will do this
by counting the number of the stages of division present in 100
green algae at a certain moment. Before we proceed to this in-
vestigation we should ask, what factors rule this number. It will
increase by 2 factors: 1. by the number of the algae (per 100)
which divide within a certain space of time, 2. by the time in
which the division of an alga is accomplished. We may say
that the l^t factor depends on the state of feeding of the algae,
tlie 2iii on the temperature. The latter was always the same in
my experiments of one series ; therefore we may consider the
time, in which the divisions of the algae took place, to be equal
also for every experiment of a same series. Consequently, we
possess in the number of stages of division per 100 algae (the
percent of stages of division), which I examined in my in-
vestigations, a direct measure, true for every series of experi-
ments, of the number of algae (per 100) which divide within a
certain, equally long space of time ; in other words, a measure of
the intensity of multiplication of these algae.

In this way we will have examined this intensity always cal-
culated per 100 green algae, which are present in a culture or
in a tussue of a sponge. The other factors (import, export, re-
duction, growth and dying), however, have been studied or will
be studied per unit of time and per unit of volume of sponge
tissue. Consequently, we have to bring also our results con-
cerning the intensity of multiplication in accordance with these
units, in order to combine all results afterwards.

Proceeding now to my investigations we see :

1. Periodicity does tiot occur in the intensitij of multiplication^
neither for the algae in the sponge tissue, nor in cultures ; nei-
tlier within 24 hours, nor within some days (Table 9). I there-
fore believe that the algae continually multiply each in its turn.

55

without any mutual regiüarity ; wliile the process of division
proceeds but very slowly (pag. 31).

2. The weaker the concentration of the algao present in a
culture or in a sponge tissue in light, the higher is their
intensity of multiplication (Table 9, 10; in sponges one should
consider the concentration at the beginning and at the end of tlie
experiment; the abnormal n^^ 3361, 341, 3651, 375, 376 should
be neglected) ; in darkness, on the contrary, the intensity is al-
ways the sanie (viz. + 0) in sponges (Table 10, conf. Table 6).
I will not examine, now, the cause of these phenomena; one
may ascribe them to the quantity of food (eg. C 0.^), the algae
can dispose of. All tliis concerns the intensity calculated per 100
green algae. Now we have to remould these results and to cal-
culate them per unit of sponge volume. We therefore should
know the mutual proportions of the various concentrations, which
we can only calculate roughly (p. 13). In this way we find in
light (Table 10 and 8, n°. 3371, 347, 3381; 3331, 3341, 343) on
the one hand an intensity (per 100 algae) of 13 with an average
quantity of algae (in the unit of volume) of VII, on the other
hand an intensity (per 100 algae) of 1 with an average quan-
tity of algae (in the unit of vol.) of XI. Now I stated that
XI = + 70 X VIL Consequently, the same sponge volume in light,
containing 100 algae in the weak concentration and therefore
possessing an intensity of multiplication of 13, must contain
in the strong concentration 7000 algae and an intensity of
multiplication of 70. Thus : in light tJie intensity of multiplication
of the algae in sponge tissue^ calculated per unit of sponge volume^
in a strong concentration, of the algae surjjasses the intensity in a
weak concentration; in darkness they are the same^ viz. 0.

3. The intensity of multiplication of the algae in the sponge
tissues as well as of those in cultures is much larger in light
than in darkness; in a sponge in darkness it is +0 (Table 10,
cf. Table 4 and 6). The concentration of the algae in every
two experiments belonging together (one in light, the other in
darkness) was generally almost the same in the cultures; in the
sponge tissues, however, in light (necessarily) even stronger than

56

in darkness. Conseqiiently, if this concentration had been equal,
the intensity of multiplication (calc. p. 100 alg.) in the sponge
in light wonld have surpassed that in darkness even more. The
cause of this phenomenon is, of course, again the state of feeding
of the algae.

This rule concerns the intensity calculated per 100 green algae;
while the concentration of tlio algae was then supposed to be
the same in light as in darkness. From this foUows : tlte concen-
tration of tJie algae being tJie same, their intensitg o f multiplication
in sponge tissue in light, calculated per unit of sponge volume,
largely surpasses the intensity in darkness.

F. The factor of mortcdity.

In chapter VI we have stated that all colourless algae present
in sponge tissues are dead or dying green ones; and in chapter
VII ^, that generally rather a considerable quantity of the green
algae is continually dying in those tissues, first changing into
colourless algae with structure and then into colourless ones without
structure (p. 45). As besides we see from Table 5 (n°. 68 p, for instance),
that there the stage of colourless alga with structure is passed
much more quickly than that of colourless one without structure,
we might in general consider through analogy also in the sponge
tissue tlie number of colourless algae with structure to be a direct
tneasure for the intensity of dying of the green algae during a
short period preceding our analysis; and the number of colourless
algae without structure, on the contrary, to be the total amount
of the algae, that died (in the same sponge volume) during a much
longer period preceding our analysis. This conclusion agrees with
the results from the analyses of Table 6 ; for there we have stated
(pag. 48, 10) that the number of the colourless algae without
structure is a 1 w a y s much larger than that of the colourless ones
with structure. This is only possible, if the first mentioned stage
of colourless ones (that without structure) is passed less quickly
than the second.

Knowing this, we may conclude from the analyses of Table 6
(pag. 46 — 47, 2, 3) that in green sponges in light as u^ell as in colour-

57

less ones in darkness : 1. the intensit;/ of dij'm(j of the rjreen alyae
remains constant in all stacjes of development of the spomje tissue^
showing hoivever a ronsiderable decrease in the fjemmule-staye; 2.
the total amount of dead ahjae increases (in the tinit of sponge
volume) during the development of the tissues, whicli is of cuurso
a matter of fact. Nevertlieless, it is important to see that tlie
latter shows from the analyses ; for it proves that these colourless
algae without structiire must hold in the tissues for rather a long
time. Is is even probable, that in full-grown tissue (at least in
the beginning) the same colourless algae without structure would
still be present, which were already there at the time the tissue
was young and growing; for their continually increasing number
can not be explained in another way (as the intensity of dying is
constant, and one should admit also that the number of dead algae,
passed at the same time from colourless ones with into colour-
less ones without structure, will also disappear at the same time
from this last stage). That the total amount of dead algae should
considerahly decrease during or after the gemmule stage is quite
conceivable, for then the intensity of dying proved much smaller,
while on the other hand colourless algae are continually dis-
appearing.

Next we want to compare the mortality of the green algae
in sponge tissue in light and in darkness. For that purpose we
can make use of both groups of colourless algae mentioned here.
First we should ask however, if in the dying of the green algae
within a sponge the stage of colourless one with, as well as that
of colourless one without structure is passed in light just as
quickly as in darkness. One might answer that this question does
not conie into consideration, as we concluded above: 1. that in
both cases the first stage is passed so quickly, that we may con-
sider it to be a measure of the intensity of dying during a short
period, and 2. that in botli cases the algae can not possibly dis-
appear from the second stage before the sponge tissue is full-grown.
This is exact. Yet I shall also answer the question experimentally,
at least as far as the second stage is concerned.

When asking this question, one thinks of a possible difference

58

of rapidity, with which the colourless stages are goue through,
as caused by : a. a changing influence produced by the green
algae on the sponge tissue (production of 0.^ and assimilates in
light, but not in darkness), h. some other influence independent
from those green algae. I will treat both possibilities in con-
nection with my experiments. In order to get a pure result, the
factors of import, (export), growth, reduction and of dying should
be excluded as much as possible in these experiments; which
may be obtained by cultivating colourless sponges (so sponges
containing a small number of green and a large number of colour-
less algae) in flowing water from the conduit, and to continue
the experiments for not too long a time. These experiments
belong to a large series of similar ones, made for different
purposes (Table 8). My material consisted in Spongillae and
Ephydatiae; generally of each sponge a piece was cultivated in
light and another piece under the same conditions in darkness.
In the beginning of the experiment both pieces of each pair
possessed an almost equally small quantity of green and of colourless
algae with structure, and an almost equally large quantity of
colourless ones without structure. Table 8, n°. 336, 365 I, 365 II,
375, 376 give an answer to the possibility mentioned sub h. For
at the end of these experiments: 1. the quantity of green algae
proves to be just as small as at the beginning, and therefore to
have been of no influence, 2. the large quantity of colourless algae
without structure in each sponge piece in light proves just as much
increased, decreased or remained equal during the same time as
in the partner sponge piece in darkness; pi'oof^ that in sponge
tissue^ when the number of green algae is small, the stage of co-
lourless alga without structure is imssed in light just as quicMg
as in darkness. Table 8, n«. 263, 264, 298, 299, 337, 338, 341—
342, 347 — 346 give an answer to the question mentioned sub a.
For at the end of these experiments: 1. the quantity of green
algae proves to have increased rather much in light, therefore
perhaps of much influence, 2. the Jarge quantity of colourless algae
without structure in each sponge piece in light proves to have
changed just as much, or more increased in the same time than

59

in the partner sponge piece in darkness; pyotjf\ fJiut in spomje
tissue^ when the nwnher of f/reen algae is important^ the stage of
colourless alga ivitJiout structure is passed in light eifher just as
quicldy or less quickly than in darkness^ hut hy no means more
quickly. Besides, this is logical (cf. chapt. VIII). Something
the like will evidently be the case, when one compares a sponge
in light containing many green algae and one containing hut a
few; for the latter will bohave almost like a sponge in darkness.

Now we proceed to the comparison of the mortality of the
green algae in sponge tissue in light and in darkness. Are there
more, or less algae dying in a sponge in light than in a sponge
in darkness?

From the results obtained through analyzing the niimbcr of
algae in sponge tissue (Table 6, pag. 46 — 48) we may immedia-
tely answer this question, if we consider that 1. in colourless
sponges in darkness the import is the only factor keeping up the
number of green algae (pag. 51), and that 2. the import is
equally active in green sponges in light as in colourless ones in
darkness (pag. 51). We may thus conclude that^ aUhouglt the
colourless sponge i?i darkness possesses miich less green algae than
the green sp)onge in light (pag. 47^ 8), still more green algae die
in the colourless spoyige in darkness — as the intensity of dying (the
number of colourless algae with structure) as well as the total
amount of dead algae (the number of colourless ones without
structure) is at its largest in the colourless sponge (pag. 48, 9).
Consequently, much more specimina of a same quantity of green
algae die in a colourless sponge in darkness than in a green
one in light.

As to this fact, one might object tjiat it might be possible
that a sponge (in light, for instance) regularly wants — it may
contain many or but a few green algae — a same quantity of these
algae to feed upon; that therefore it would not be of any use to
calculate the mortality per same number of green algae, as then
one would find, of course, a large relative amount of dead algae
in a colourless sponge, even if it did not grow in darkness.
ïhis reasoning might be exact, certainly (see below); but in any

60

case we have stated here, tliat even the absolute amount of dead
algae in the colourless sponges in darkness surpasses that in the
green ones in light.

I will prove also by direct experiments, that of a same quan-
tity of green algae in sponge tissue — in other words, the concen-
tration of the green algae being the same — more algae die in
darkness than in light. Also here the factors of import, (export),
reduction and growth should be excluded as much as possible
in the experiments; that of multiplication can not be excluded,
but it will not be of influence on the results. For that purpose
we cultivate green sponges in flowing water from the conduit
for not too long a time. See Table 8, n». 100, 260, 261, 292,
293, 294, 333, 334, 343—344, (357, 359) — (348, 356, 358),
366 I, 366 II, 371, 372; all of them green Spongillae and
Ephydatiac. Generally of each sponge a piece was cultivated in
light and another piece under the same conditions in darkness.
In the beginning of the experiment both pieces of each pair
possessed an almost equal and large quantity of green algae, an
almost equal and small quantity of colourless ones with structure
and an almost equal and moderate quantity ot colourless ones
without structure. Now, during the experiments the number of
green algae generally proved to have more decreased and the
number of colourless algae with structure and that of colourless
ones without to have more increased in the sponge pieces in
darkness, than in the partner sponge pieces in light during the
same time. So it is clear, not onlij from the intensity of dying
(number of colourless algae with structure) hut also from the total
amount of dead algae (numher of colourless ones without structure),
that m sponge tissue, when the concentration of the green algae is
the same, much more algae die in darkness than in light (calcu-
lated per unit of time and of spoyige volume). (In some experi-
ments — n''. 344, 348, 358, 366 I, 366 II — the number of
colourless algae with structure has decreased at the end in the
sponge in darkness, or has remained the same. Evidently this
is caused by the already very much progressed decrease of the
green algae (by dying), for the number of the colourless ones

61

without structure proves in all these cases, that also here more
algae dicd in darkness than in light).

I want to point out emphatically that we got tliis result by
means of experiments in which the spongés in light contained a
large quantity of green algae. We therefore know (pag. 59)
that in these experiments the stage of colourless alga without
structure can not have been passed more quickly in the sponges
in light than in those in darkness, but that it has been passed
just as quickly^ or even less quickly in light. When we suppose —
to get a pure comparison — this stage to have been passed just
as quickly in both cases, the above obtained result must be
binding, perhaps even a fortiori.

One should also examine, if there is any difference in the in-
tensity of dying of the green algae in the tissue of a sponge
with a strong and in that of a sponge with a weak concentra-
tion of green algae. To answer this question we may mutually
compare the number of colourless algae with structure in green
and in light-green sponges, after these sponges have been culti-
vated for some time in water from the conduit, in light or
in darkness (Table 8). At first after culture in light. We find
this number in 27 green sponges : 1 II -|- 2 III + 7IV4-10V4-
4 VI + 3 VII and in 18 light-green (or colourless) ones : 1 I +
1 II + 2 III + 3 IV + 4 V + 4 VI + 3 VII. So it follows that in
light the intensity of dying of the green algae in sponge tissue in
a weak co7icentration is almost just as large as in a strong con-
centration of the algae (calculated j;er unit of sponge volume).
Then the same for sponges cultivated in darkness. In 8 green
sponges the number of colourless algae with structure proves to
be : 1 II + 1 III + 1 V + 3 VI + 2 VII, and in 37 light-green (or
colourless) ones : 2 I + 5 III + 8 IV + 4 V + 10 VI + 8 VII. Con-
sequently, in darkness the intensity of dying of the green algae
in sponge tissue in a weak concentration is somewhat smaller than
in a strong concentration of the algae (calculated per unit of
sponge volume).

When we consider both these facts in all experiments of Table
8 (with respect to the concentration of the green algae in the

02

beginiiing and at the end of tlie experiments), the above obtained
result (p. 60) — that more algae die in darkness than in light —
remains valid ; then there are even some more experiments
leading to the same resnlt: n'\ (246, 248) — (255, 256), 339,
340, 367, 368, 369, 370, 374, 378—377. Moreover, the exact-
ness of this result — not only for a same strong- concentration
of the green algae, but also for a same weak one — also follows
very clearly from the last two argumentations.

Finally I should mention that we have realized the faet in
these cultures of green sponges in aquaria in darkness, that of
all 6 factors, normally ruling the number of algae in sponge
tissue, only the factor of dying has (practically) remained.

Afterwards I will treat the cause of the dying of the algae
in sponge tissue, when speaking about the symbiotic relation of
sponge and alga.

V-

Having studied the 6 factors ruling the number of symbiotic
algae in sponge tissue separately, we are now going to examine,
if some combinations of those factors can be realized. We will not
take into consideration the uncertain factor of export, the ab-
normal ono of reduction and the but slowly werking factor of
growth, in order to combine the 3 principal factors of import, of
multiplication and of dying :
I. Import + multiplication can not bo realized, of course.
II. Import + dying is realized, together with growth, in nature
in colourless sponges in darkness. See Table 6.

III. Import + multiplication + dying is realized, together with
growth, in nature in green sponges in light. See also Table 6.

IV. Multiplication + dying can be realized by cultivating green
and colourless sponges in flowing water from the conduit in light
and in darkness for not too long a time; in this way the factors
of import, (export,) reduction and of growth will be excluded as
much as possible. These experiments are very important ! For ive
will succeed in this icay to transmute green sponges into colourless

63

ones hl/ culture in darkness and colourlcsy spongen info (/reen ones
hy culture in light^ uifh the smallest nmnber of active factors
possihle. Consee/uently ^ we must succeed in explaining these plieno-
me.na, the interpretation of whirh has heen songht for ever so long
in quife a wrong direetion (pug- -^0 — 41)^ as hei)tg caused hg tlic.
comhined arfion of the nmltiplieation a?id tJie mortality of the
green algae in the sponge tissues^ in light and in darJaws.s. Seo
Table 8, all n^s (all green and colourless Spongillae and Ephy-
datiae) ; generally of each sponge a piece was cultivated in liglit
and anotlier piece under the same conditions in darkness. In each
piece the colour and inostly also the amonnt of algae in its
tissues was accurately examined at the beginning and at the end
of the experiment.

In general we distinguish 3 types of sponges in respect to their
behaviour during the experiments. In type I the green colour,
so the number of green algae (as the experiments show), increases ;
in other words the increase of green algae surpasses the de-
crease. In type III the green colour and the number of green
algae decrease, in other words the increase of the green algae
is smaller than the decrease. In type II the green colour remains
constant as well as the number of green algae, or the green
colour or the number of green algae changes a little by increase
or decrease ; in the last case but one we niay speak of a type
II'; in the latter of a type II"f.

We see from the table:

A. 1. From 92 Spongillae, cultivated in light, behaved like
type I 60 )

„ II 22 = 22 = + 24%
IIi'i 2 )

lm 5 h ^ = ± «°'°

If we consider, ho wever, that under type II 21 already ori-
ginally green coloured sponges occur — in which some decrease
of the green colour could probably have been observed very well,
some increase but very difïicultly — we are justified in neglecting
those 21 specimina. Than we would find:

64

Froin 71 (=92 — 21) sponges in light behaved like
type I+IIi 63 = + 89'

„ II 1 = + 1°/

„ Ilm + m 7 = + 10%

'°/o

o

Consequently, in the greater majority of Spongillae, when culti-
vated in liglit, the increase of the green algae proves to surpass
the decrease. Accordingly, we saw that in light : a. most colour-
less to light-green Spongillae (61) became groener (or at least
increased in number of green algae) ; but once this did not happen ;
h. most green Spongillae (23) maintained their colour ; but in 7
sponges the green colour diminished (so here the decrease of the
algae surpassed the increase).

2. From 32 Spongillae cultivated in darkness behaved like

1=4= + 13%

type I O
„ IIi 4

„II 3=3=+ 9%

lm 23 1 = 25 = ± '«°/°

•

Consequently, in the greater majority of Spongillae, when cul-
tivated in darkness, the increase of the green algae proves smaller
than the decrease. Accordingly, we saw that in darkness : a. most
green to light-green Spongillae (25) lost, or at least diminished,
their green colour ; only once it remained constant ; h. the colour-
less Spongillae (6) remained colourless, though in 4 pieces the
number of green algae appeared to have somewhat increased.

B. 1. From 34 Ephydatiae cultivated in light behaved like

type I 14
. IIi 4

= 18 = + 537,

0/ ,
o

o /

II 4 = 4 = + 12

Iliir 4

III 4 ! = 12 = + 35°

o

o

„i,ni, 4

Consequently, in the majority of the Ephydatiae also, when cul-
tivated in light, the increase of the green algae proves to sur-

05

pass tho decrease. Accordingly, we saw that in light: a. most
colourless to light-green Ephydatiae (15) became greener (or at
least increased in number of green algae), that but few specimina
remained colourless (3) or even decreased in number of green
algae (3), while others became greener in the beginning in order
to lose their colour entirely afterwards (4) ; h. the green Ephy-
datiae sometimes kept up (3), sometimes even increased (2),
several times however considerably decreased (4) their green
colour. So it proves that in general Ephydatia in light behaves
like Spongilla; but that even under these circumstances it pos-
sesses a strong tendency to become colourless.

2. From 37 Ephydatiae cultivated in darkness behaved like

II 13 =13 = + 35%

. I, III 4=4=+ 11"/,

If we consider, however, that under type II 12 already origin-
ally colourless sponges occur — in which some increase of the
green colour could probably have been observed very well, but
no decrease can possibly have been observed — we are justified
in neglecting those 12 specimina. Then we would find :

From 25 (= 37 — 12) sponges in darkness behaved like

type I + IIr 2= 8%

n 1 = 4°/,

„ II"i + ni 18 = 727
„ I, III 4 = 167

o

0/

o

Consequently , in the greater raajority of Ephydatiae, when
cultivated in darkness, the increase of the green algae proves
smaller than the decrease. Accordingly, -we saw that in dark-
ness: ff. most green to light-green Ephydatiae (11) lost their
green colour, but 1 kept-it up; b. the colourless Ephydatiae ge-
nerally remained colourless (12) or even lost green algae (7);

5

66

bilt in 2 specimina the number of these algae increased, while
4 other ones became greener in the beginning in order to lose
all colour afterwards. So Ephydatia in darkness proves to behave
like Spongilla.

C. Finally 8 sponges of unknown genus, cultivated in light;
4 behaved like type I and 4 like ^type II. Siich a sponge cul-
tivated in darkness behaved like type UI.

The residfs of our experiments may be resumed as foUoivs:
1. Green Sjmïigillidae remain green in light. 2. Colourless Spongil-
lidae remain colourless in darkness. 3. Colourless Spongillidae be-
come green in light. 4. Green Spongillidae become colourless in
darkness. 5. When Spoyigillidae are cultivated in light^ the increase
of the green algae surpasses the decrease. 6. When Spongillidae
are cultivated in darkness, the decrease of the green algae sur-
passes the increase. I want to point out emphatically that these
residts were obtained by cultivating the sponges under such cir-
cunistances, that the factors of import, export, reduction and of
growth were almost entirely excluded. Consequently , the facts stated
here must . necessarily be explained by the two remaining factors :
that of multiplication and that of mortality. Therefore the results,
given in these factors, run in the following way :

1, 2 for green sponges in light and colourless ones in darkness : mu = mo (I)

3, 5 for light-green and colourless sponges in light : mu > 7no (II)

4, 6 for green and light-green sponges in darkness: mu<imo(in.)

(mu = factor of multiplication, mo =^ that of mortality)

Proceeding from formula I, we will now prove the exactness
of the other formulae by means of the above obtained data
(p. 55 — 56, 60, 61) concerning the factors of multiplication and
mortality. This is quite simple. We proceed from a green sponge
grown in an aquarium in light; for this formula (I) mu = mo is
binding. What happens, when we transfer this sponge into an
aquarium in darkness? Then this green sponge must pass into a
colourless one — according to our data. We may symbolize this
transition in this way:

mu —

0

mo

V

A

mu < ^]

)mo

V

mu <

mo

V

mu —

mo

67
green sponge in light:

green sponge transferred into darkness

T

t

light-green sponge in darkness :

1

colourless sponge in darkness:

Now the reverse : proeeeding from a colourless sponge grown
in an aquarium in darkness (so : mu = mo). What happens when
we transfer this sponge into an aquarium in light? Then the
sponge will become green:

colourless sponge in darkness : mu = mo

A V

colourless sponge transferred into light: mu > mo

I ^ A II

light-green sponge in light: mu > mo

I

green sponge in light : mu = mo

I am not going to treat this question at large now, for I will
soon come back to it, when treating the behaviour of the sponges
in nature.

^.

Having examined the 6 factors, ruling the numher of sym-
biotic algae in sponge tissue, as well as some of their chief com-
hinations, we will trij to answer the ahove (p. 48) mentioned
questions, concerning Spongillidae in free nature, hij means of the
data we have obtaified in the mean time.

1) < is stroBgei- than <, ^ is stronger thaa <.

68

I. The question , why green as ivell as colourless algae oecur in
sponges in ligJit as icell as in darkness. Because in sponges in
light import, multiplication and dying of green algae takes place,
import and dying in sponges in darkness.

II. The very important question, directly corresponding with
that of the foregoing pages, n-hy in nature a sponge in light
contains an excess of green algae^ consequently it is green; why a
sponge in darkness contains a small numher of green algae^ con-
sequently it is colourless; how a green and a colourless sponge
arise from each other.

The data, we will make use of, concerning the factors of im-
port ') (ï) (pag. 50, 51), export (e) (pag. 52), reduction (r) (pag.
52 — 53), growth (g) (pag. 53), multiplication (mu) (pag. 55 — 56),
and of mortality (tiio) (pag. 60, 61) are printed in italics on
the pages mentioned here.

I want to point out emphatically that all these data have
been calculated per unit of time and per unit of sponge-volume,
while the facts resulting from Table 6 (pag. 46 — 48, point 1 — 11),
which we have got to explain here, are also calculated per
same units.

We now imagine a sponge (containing an arbitrary quantity
of green algae) keeping constant its colour, therefore its num-
ber of green algae. For this number the following formula
would be binding:

« + r + mu = e -{- g -{- mo

An equation of balance: the number of green algae added per
unit of time in the unit of sponge-volume continually counter-
balances the number which is substracted. Now we know that
in nature a (green) sponge in light as well as a (colourless) sponge
in darkness really keeps up its colour for a long time (pag. 35).
Consequently, this formula is binding for their quantity of
green algae. •

1) If the import in green sponges in light might prove greater thaa that in
darkness (p. 51, note), the following argumentations would be binding a fortiori.

69

A. If in nature such a sponge containing an arbitrary number
of green algae and growing in light — for its green algae
then we have i -\- r -\- mii = e -]- f/ -\- mo (I) — is transported into
darkness, what is going to happen then? The multiplication of
the green algae must then become much smaller (= + 0), the
mortality much more intensive ; while the import remains the
same, also the export (at least in the beginning), but the growth
of the sponge will probably decrease immediately and the reduc-
tion remains the same (= 0). The original equation i -\- r + >}iu =
e -\- g -\- mo passes into i -\- r -\- niii < ^ + 5' + ^^^^ (H)* The ba-
lance is broken, the sponge must continually lose green algae,
therefore become more and more colourless. In consequence of
this decrease of the concentration of green algae the import, the
reduction and the multiplication do not change, the mortality how-
ever decreases as well as the export, while also the factor of growth
will be diminished ; but the formula i + r -\- mu < e + ^ + >no
remains binding (III). Consequently, the end of this process must
be that all green algae disappear from the sponge tissues, the
sponge itself becoming perfectly colourless. Then, of course,
also the second part of the formula e + ^ + ^no must decrease
automatically till it has become equal to i + r + ww, so till a
balance i + >' ~\- nm = e + g -\- mo is re-established (IV) ; but now
another than the original one. So the mortality must have dimi-
nished ; nevertheless it is then still strenger than in the begin-
ning (p. 59), and rather considerable. When this state of per-
fectly colourless sponge in darkness is reached, the import is
still rather considerable, the factor of growth has diminished
still more and the multiplication, the reduction, and the export
are + 0. In stead of i -\- r -{- mu = e ^ g -\- mo we may put
i = g -\- mo ; in fact even / = mo. In other words, in such a
colourless sponge in darkness the whole import is always counter-
balanced by the mortality (and the growth).

We may symbolize the transition mentioned, in the fol-
lowing way:

70

(I) green sponge in light:

(II) green sponge transported into darkness:

I

(III) light-green sponge in darkness:

■

(lY) colourless sponge in darkness :

i -\- r -f mu = e -{- g -\- mo

V

V A

i + r + mu < e + (jr + ino

11 II II V V VA
i + r + nm < e + </ + ''>'o

II II II VVV
ï + r + mu = e + </ + mo

\

i + 0+ 0=0 + ^ + mo

II II II

i =z g -\- mo

l t

mo

From this we see that, if in nature a sponge containing an
arhitrary numher of green algae, so a more or less green sjwnge,
wJiich grew in light and kept up its colour, is transported into
darkness^ it must unavoidahly José all its green algae and accord-
ingly become colourless itself^ especially in consequence of a very
miich decreased multiplication and a stroïigly increased mortality
of tJiose algae in darkness. When all green algae have disap-
jyeared, the sj^onge is able only hy continually importing new ones
from outside to keep up a very small numher of green algae in
its tissues, as these too continually disappear hy dying (conf. Table
6 and p. 47, 3).

B. Now the reverse. What will happen, when a sponge in
nature containing an arbitrary small number of green algae,
which grew in darkness and kept up its colour, is transported
into day-light ? In darkness the formula ^ + r + mu ^e -{- g -\- mo (I)
was binding for its green algae. Now, in light the multiplication
of the algae must become much more intensive, the mortality
much lower, the import remains the same, also the export (at
least in the beginning), while the factor of growth (in the be-
ginning) as well as the reduction (= 0) remain the same. The
original equation i + r + mu = e -\- g -{- mo passes into ^ + r +

71

mu > e + g + mo (II). The balance is broken, the sponge keeps
more and more green algae, therefore becomes green itself. In
consequence of this increase of the concentration of green algae
the multiplication increases, the mortality, the import and the
reduction remain the same, but the export and certainly also the
factor of growth must increase little by little. The formula
^ + >• + mu > e -\- g ^ mo however remains binding (III). The end
of this process must be, that the sponge lodges an excess of green
algae in its tissues, it therefore becomes dark-green itself; even
there would not seem to come an end to the increase of the
number of green algae in this way. That is impossible, of course;
in such a dark-green sponge the factors must change in such a
way, that at last this perpetual increase ceases. This changing
is again the consequence of this great increase of concentration
of the green algae : although the multiplication has still increased —
it is considerable and much more intensive than in the beffinning;
(Table 10) — and the mortality has remain ed the same — it
is moderate and much lower than in the beginning (pag. 59) — ,
the factors of growth and export have certainly strongly increased,
while the import has remained the same (rather considerable) as
well as the reduction (= 0). In this way a new balance {-{-r-i- mu
= e -]- g + mo must arise in the dark-green sponge in light (IV) —
of course another than the originally existing one.

We may again symbolize the transition mentioned, in the fol-
lowing way :

(I) colourless sponge in darkness

(Tl) colourless sponge transported into light: i + r -j-

\ II II

(III) light-green sponge in light

T
t

(IV) green sponge in light:

i + r + ^ mu ^: e + g -\- mo ^

A II II V

jitii > e ^ g -\- mo

AA AA II V

mu > e + g + mo

A A A II
)nu = e -\- g -\- mo

i + r -\-
II II

O

72

hl tliis way ive find that, if in nature a sponge containing an
arhitrary small numher of green algae, so a more or less colour-
less sjjonge, which ivas growmg m darhiess and kejjt up its colour^
is transported into daglight, it must unavoidahly accumulate a
large quantity of green algae in its tissues and therefore become
dark-green itself, especially in consequence of a strongly increased
multiplication and a much decreased mortality of those algae in
light. When the wJiole tissue is crammed with green algae, the
various factors ruling their numher change in such a manner,
fhat a new balance is established; these changes are an increase
of the groivth of the sponge and p)erhaps also of the export of
green algae.

(I have always put the export to account. It is, however, an un-
certain factor, as I have stated. One may therefore leave it out
entirely. That would be of no consequence to the argumentation).

Up to now my argumentations have set forth from sponges,
which kept up their colour and, therefore, showed the equation
of balance for the number of their green algae (p. 68). But the
same can be proved for sponges changing their colour: as we
proved that a dark-green sponge from light becomes colourless
in darkness, it is a matter of course that a sponge, which grew
green or colourless in light (therefore, a still more or less light-
green sponge) must also become colourless in darkness ; while the
reverse will be the case for sponges, which were growing colour-
less or green in darkness, and were then transported into day-
light. The questions, why in general a green sponge in light
remains constantly green, and a colourless one in darkness con-
stantly colourless {i + r -f mu = e -\- g -\- mo), have in fact been
answered already above under B and A (pag. 69 — 72). Also other
questions may be proposed and answered in the same way.

We have stated now, that (and why) generally in nature 1. sponges
in darkness must become colourless and sponges in light green,
2. greeyi sponges in light and colourless ones in darkness must
keep up) their colour.

73-

(I want to point out einphatically that, up to now, I have
exclusively spoken about the normally occurring cases; I will
treat the exceptions below.)

III. Now we come to the question, wltij in nature a sjjonc/e in
light — so a green sponge — contaitis a moderate numher of co-
lourless algae and a sponge in darJmess — so a colourless one —
rather a large numher of these algae.

Also here we can make use of an equation for the nuniber
of dead (colourless) algae :

>

i + r + mo = e + g -\- d

<

(The letters stand for the same as in the formulae above ;
d means the number of colourless algae disappearing (by solu-
tion) in the unit of time from the unit of sponge-volume).

We know, however, that i = O (pag. 51), r = O (pag. 53),
e= ± O (pag. 52), and d= ± O (at least before the sponge is full-
grown: pag. 57). So we get;

>

mo = g

<

of course it is (p. 57),

eg. for a green sponge in light: mo )> g

A V
consequently for a colourless one in darkness : mo > g

as will show from the data given on pag. 60 — 61 and 53. So we
see that in the same time the number of colourless (dead) algae
nmst increase much more in the sponge in darkness than in that
in light.

Lateron I will treat, why the number of colourless algae with
structure remains constant during the development of the sponge
tissue (chapt. VIII). Why that of the colourless ones without
structure increases is mentioned on pag. 56 — 57.

74

colourless sponge in darkness:

IV. Why does the number of the various (green and colourless)
algae always shotv a decrease in the gemimde stage ?

As for the green algae, we may symbolize the transition of a
colourless sponge in darkness into the gemmule stage as follows :

i i + r + mu = e + g ^ mo

j II II II II II II

1/+0+0 = 0 + g + mo

V A II II V

young colourless gemmule in darkness : 0+/'+0 0+0+ mo

I II V 11 II II V

old colourless gemmule in darkness : 0+0 + 0 <(0 + 0 + mo

\ A II II II A A

germinated gemmule in darkness : i + 0+0 0 + (/ + mo

Consequently the green algae must entirely disappear from old
colourless gemmules in darkness, in order to re-appear immediately
in small numbers, when the gemmules have germinated (conf.
pag. 47, 3).

The transition of a green sponge in light into the gemmule
stage may be symbolized :

■ i + r + mii = e + g -i- mo
green sponge in light: -» II II II II II II

^ + O + mu = e -\- g -\- mo
VA V V

young green gemmule in light : O + r + mu O + O + mo

I II V V II II V

old green gemmule in light : 0+0+0 <(0 + 0 + mo

J A II A A A A

germinated gemmule in light : / + O + mu e -\- g -\- mo

Consequently, the number of green algae must decrease in old
green gemmules in light, but probably increase immediately after
the gemmule has germinated (conf. pag, 46, 2). The fact, that
the multiplication of the algae stops in old green gemmules, is
stated on pag. 46, "Z, There are several reasons possible for it;
none of them can be proved, however.

75

The deercase of the number of cohmrless algae with structure
in the gemmule stage will be explained lateron, when speaking
about the cause of the dying of the algae in sponge tissue, But
I want to remind that we concluded (pag. 42) that this dying
is closely related to the life of the sponge ; and we know that
the gemmules are stages of rest of the Spongillidae. So it is
evident that probably herein is the cause of the decrease of
the mortality during that period. That the. total amount of dead
(colourless) algae (without structure) decreases in the gemmule
stage, has been explained already on pag. 57.

hl this way we have proved with the help of the data ice oh-
tained^ when studying tlie 6 factors (of import^ export^ reduction^
groivth, multiplication and mortality) ruling together the number
of the symhiotic algae in sponge tissue: 1. Why in nature the
Spongillidae must contain such an amount of the various green
and colourless stages of the symhiotic algae in light and in dark-
ness, as we have exj)erimentally stated on pag. 46 — 48,pointl — 11.
2. Hoiv in nature these sponges keep up their ^colour^' (green or
colourless)^ and how both ,^coulour'"-types arise from each other
(pag. 35).

As mentioned above, up to now I have exclusively treated the
cases normally occurring in nature, viz. those of green sponges
growing in light and colourless ones growing in darkness (pag. 46).
We stated, however, that sometimes green sponges might be found
in nature in darkness and colourless ones in light (p. 41); and
in Table 8, pag. 63 — 66, that as an exception to the rule green
sponges may become less green in light and colourless ones more
green in darkness. How is that to be explained?

We saw that the amount of green algae, so the colour of the
sponge, is ruled in nature by the proportion (/ + r + mu) :{e + g
+ nio) and in my experiments by mu : mo. We must consider,
however, that each of these factors is depending on numerous
circumstances. These circumstances proved in general rather con-

76

stant — for we could deduce several generally appliable rules
concerning these factors, by which could be explained the nor-
mally occurring cases of changing or remaining constant of the
number of green algae in sponge tissue (in light or in darkness).
But this fact does not at all exclude the possibility, that these
circumstances do change — as an exception. In such cases our
rules, deduced for normal circumstances, would not be binding
of course.

In such a way one will have to explain the abnormalities
mentioned. When analyzing now the amount of algae present in
these cases (Table 6 B), we find : in grepn sponges in darkness
the multiplication to be normal — very slow — but the mor-
tality abnormally low ; in colourless sponges in light, on the
contrary, an abnormally slow multiplication and a normal mor-
tality. By these facts the abnormalities become already more
conceivable.

VIII. The nature of the „symbiotic" association of sponge

AND GREEN ALGA ; ITS USE TO THE ALGA AND TO THE SPONGE.

This part of my investigation has indisputably been the most
difficult one. Only after much groping, I succeeded in finding a
way out from the labyrinth of facts, which bear upon these pro-
blems ; not by lack of points of issue, but even more by their
great number, however partly leading — at first sight — in
opposite directions.

a.

I irill begin ivith the use wJdch the ,,symbiotic^^ association
offers to the alga.

In the first place this question: How shall we state whether the
algae are in better conditions in one milieu ■ — eg. a sponge — or
in another? We want to state the use of the „symbiosis" to the
alga, in other words : if the alga is in a better condition in the
sponge tissue than in the water. Which phenomenon on the alga
shall we take as criterion?

77

Only two criteria are to be considered, as being most self-
evident: Ist the intensity of the multiplication of the algae,
2nd the total increase of an algal-culture within a certain time.
It appears less desirable to me to accept a criterion in the ap-
pearance of the algae, viz. in the more or less normal or dege-
nerate condition in which they are, as it must be very difficult
to apply.

So there remains : tlte mtensiti/ of multiplication (the number
of stages of division per 100 green algae, see p. 54) and the
total increase of an algal-culture. Perhaps one will suggest
that both these criteria come to the same in fact ; but this is not
the case at all. The intensity of multiplication gives a waij of
measiiring the favourableness of the conditions imder which every
alga individually lives, for instance of the feeding milieu (apart
from factors which, in short, destroy those algae). The total in-
crease (or decrease) of an entire culture, however, is a measure for
tJie favourableness of all factors, which possihhj can be of amj
influence to the algae. So it may be that, though an alga finds
somewhere a favourable feeding milieu, by which it multiplies
rapidly, the whole culture is exposed to such a degree to the
gluttony of protozoa, that after all the number of algae is de-
creasing instead of increasing.

So it is most important to apply both criteria in our investigations.

Comparing a sponge (in light) and lake water (in light) with
regard to the question we are treating presently, we notice first
and premost the enormous difïerence in concentration of the green
algae. The sponge is grass-green or dark-green, the water from
the lake never has a green tint; the sponge contains numbers
of green algae in its tissue (one could take 3 X 10" green algae
per litre), the water from the lake only 4000 per litre (p. 28),
at the end of July.

I have stated in chapter VII, that sponges in nature constantly
increase their number of green algae by import. So at any rate
the accumulation of algae in a green sponge is already partly
explained by this mechanical process. But import onl) is not

78

sufficiënt — just think of the colourless sponges in darkness with
an import just as large (but with a much smaller multiplication
and a much greater mortality) — also a rather considerable
multiplication is required and low mortality.

What about this multiplication and this mortality of the green
algae in a sponge, compared with those phenomena in algae free
in the water? Is in light the intensity of multipUcation in a
sponge larger^ the same or smaller than in water?

For this see Table 10, to which I have already referred
several times. In this table there is given every time in column 1
the intensity of multiplication of the green algae for a sponge in
the light (and in the dark) and for a culture in water from the
conduit or from the lake in light (and in darkness). From that
we see that in most experiments the intensity in the water is
ever so much larger than in the sponge ; in the latter it is
generally below 15, in water it amounts to 20 — 35 !

Let us, for the present, not ask how that phenomenon in caused ;
at any rate it goes without any doubt for these experiments.
No-w what ahout the total nmnber of green algae when cultivated
in light in sponge and in water? See Table 10, column 3. That
number proves, notwithstanding the much larger intensity of mul-
tiplication in water, in general in water less increased than in
the sponge. So it cannot be otherwise than that the algae, which
have much more multiplied in water, must also have been more
destroyed there, in some way or other, than in the sponge. (With
all these experiments the factors of import, export, reduction and
of growth were excluded as much as possible). So all things
together, the algae in the light are in more favoiirahle conditions
in the sponge than in the water; really the sponge must protect
its algae against destruction '),

This fact must also inevitably appear, when we notice that,
according to Table 8, entirely colourless sponges with only few

1) To get this result puiely, we must compare the algae with equal begin-concen-
tiation in sponge tissue and in water from conduit, of couise, after they have been
cultivated for the same time and at the same temperature. Then consider what is stated
in the following pages (p. 82 — 83).

79

green algae, ciiltivated in light in water from the conduit (so
excluding import), soon show a larger amount of green algae
than the water of the lake ever possesses.

It is rather well conceivable, although not quite sure, against
what the sponge protects its algae. A priori one supposes this
protection to be against protozoa and other small fresh-water
organisms which will swallow the algae. Also in my cultures I
have got an indication for this, as shown in Table 9 B. There one
sees, among others, an algal-culturo in light in small concentra-
tion in water from the lake, which the 2'^d week consisted of a
ihin green membrane surrounded by a (newly formed) darker
green rim. During the Srd week, however, first the rim and next
also the membrane suddenly begins to disappear. Now, numerous
protozoa prove to have grown in the culture ; among which there
are some filled with the green sponge algae. About a week later
the whole algal-culture has almost been destroyed ; numbers of
degenerate algae remained, while the protozoa disappeared for
the greater part.

Besides, there exists also a means of protection for the sym-
biotic algae within the sponge body against other enemies, not
enemies which will swallow them, but which cause their destruc-
tion in some other way : diatoms and ordinary algae. Above
(p. 43, 45 and Table 5) I treated already, how the sponge algae
were killed by an infection of diatoms or algae arising in the
culture. I do not venture to decide, to what this influence must
be ascribed ; one might suppose to (lack of food or to) poisoning
by products of metabolism, especially as the same thing happens
when mould-infection occurs (p. 43). It is obvious, now, that this
influence of the infecting algae and diatoms will be strenger in
light than in darkness; which, moreover, appears from Table 4.
So it might be possible, that a culture of symbiotic algae in
water and in light, with of course a high intensity of multipli-
cation, has in fact less increased after some time — by the hurt-
ful influence of luxuriantly growing algae and diatoms — than such
a culture in darkness, with but a small intensity of multiplication.
In Table 10 there are indeed some of such cultures to be seen.

80

So here we have siich an (apparently) paradoxal phenomenon,
as treated above in consequence of the comparison between multi-
plication-intensity and total increase of the algal-culture in a
sponge and in water; indeed, here too we found a smaller total
increase with a larger multiplication-intensity of the symbiotic
algae (in water).

So one proof more, that this intensity of miiltiplication
and this total increase are independent factors ; while, what
we treated just now, gives even more support to the above
mentioned opinion, that the protection of the symbiotic algae by
the sponge is, among others, also meant against diatoms and
ordinary algae.

It stands to reason, that this protection must now not be taken,
as if there are no algae destroyed in the sponge itself. Of course
this does take place, as we saw, eg. on p. 46 — 48.

On p. 78 we saw that in the cultures of Table 10 the intensity
of multiplication of the green algae in light was generally much
higher in water than in the sponge tissue. I have purposely
omitted till now treating the cause of it, to evade unnecessarily
complicating the question we were about.

Yery likely that cause is not to be found in the milieu, in the
sponge or the water, but in the concentration-diiïerence of the
algae themselves (see p. 55). It might seem to be very difficult,
almost impossible, to directly compare the concentration of the
algae in water and in the sponge tissue somewhat accurately.
Nevertheless, I believe to have succeeded rather well ; and I so
came to the conclusion that in fact in the light, in an equal,
strong concentration of the green symbiotic algae, their intensity
of multiplication in water and that in the sponge are probably
the same.

In the first place we see that in Table 10 there are also cases
to be found in which the intensity of multiplication in the sponge
is just as high as that in water, or just the reverse, that the
intensity in water diminishes down to that in the sponge. The
first regards sponges with weak concentration of the green algae

81

— consider botli begin- and final concentration — '); the latter
cultures with a strongcr concentration, compared with othcr cul-
tures. So wc see that, when we consider the concentrations, the
found intensities of multiplication in sponge and water seem to
approach each other. This appears even more clearly, when we
compare some intensities in the sponge tissue found in Table 10
with the intensities in water with different concentrations of the
algae, stated in Table 9. (Here the concentrations have namely
boen more accurately established.) We then see that in the sponges
8371, 3381, 347, 3701, 416, etc, all of which are sponges with
weak concentration of the algae, a multiplication-intensity ruled,
which was equal to, even larger than that of the algae in a
strong concentration irr the water-cultures of Table 9. So this
was an indication the more in the^above mentioned direction.

The question was how to compare these concentrations of the algae;
so in a culture in water, that is (p. 10) a membrane attached to
bottom, and in a more or less green sponge. Of course it is impos-
sible to fix the number of algae in equal volumes of sponge and cul-
ture. There only remains the comparison of the colour. Thereto
one should consider that one can state the colour of the green mem-
brane on a white and on a dark background. For a colourless or a
green sponge one can say, that the background is white (creamy).
Therefore the sponge may be compared directly, as regards its
colour, with a membrane on a white (creamy) background.

Apply this on Table 9. ït then appears, that in A the mem-
brane in the strong concentration on a white background is yellow-
green to light-green, the rim (just as the sponge) dark-green; in
the weak concentration the membrane greenish, the rim light-
green to green. In B the sponge is dark-green, the membrane in the
strong concentration on a white background green to light-green ; in
weak concentration the membrane greenish, the rim light-green.
Let us now stick to Table 9 A ; this one has been continued
longest and is the most accurate, as there was no question about
infection, as was in the other one. So we see that with a dark-

1) Nos 3361, 341, 3651, 375, 376 should be neglected as being abnormal.

O

82

green colour, so in a concentration s. of the algae, the intensity
of multiplication is the same in the sponge as in the water-
culture, viz. about O — 6.5 (once 9), on the average 2 in
the sponge, in water 2.3 ; with a yellow-green to light-green
colour, so in a concentration m., in water about 7 — 20 (once 28),
13 on the average ; with a greenish colour, so in a concentration
w., in water about 29 — 39 (once even 45) and 33 on the average.

We should also apply this method to Table 10 and first to the
sponges in light, considering again both, begin- and final con-
centration of the algae. We then find in a concentration s. — S.
of the algae in the sponge a multiplication-intensity (in 22
out of the 23 cases) of about O — 7 (once 9), 2.6 on the average;
in a concentration m. — s. (in 14 out of* the 18 cases) of about
5 — 11 (once higher, 3 times lower), 7 on the average; in a
concentration w. — m. (in 12 out of the 15 cases) of about 9 — 17
(once lower, twice very low), 10.7 on the average ; in a concen-
tration w. — s. both very low values for the intensity of 3 and 7 ;
and finally in a concentration w. — w. (in 3 out of the 4 cases)
an intensity of about 15 — 20 (once lower), 15.5 on the average,
while the experiments n°. 3361, 341, 36511, 3751, 3761, with
the concentration w. — u\ and their multiplication-intensity of O,
should be neglected as being abnormal (p. 75 — 76). For the cul-
tures in water from the eonduit in light we find: in a concen-
tration s. — s. an intensity of 1; in a concentration m. — m. of
11 — 23, 15.7 on the average; in a concentration w. — m. of about
19- — 28, 23 on the average; and in a concentration w. — w. an
intensity of about 17 — 37 (once 10), 25.2 on the average. For
the cultures in lake water these values are generally lower ; as
also in Table 9 B.

One will acknowledge that, considering the rather coarse way
of comparing the concentrations of the algae in the sponge tissue
and in the water cultures, their multiplication-intensities for the
strong concentrations (.s. — s. and m. — s.) in sponge tissue and in
water do mutually correspond very well in Table 9A and 10');

1) In fact we ought to have stated them separately in Tablo 10 for each series of
experiments (p. 54); the lesult, however, would have been the same.

83

while tliüsü for the weak conoontrations {ir. — m. and w. — w.)
are lower in sponge tissue than in water. But, of course, the
correspondence of the intensities for the concentrations s. — s. and
fn. — s. is the most decisive. So we are justified in concluding
that the sijmhiotic algae multiphj in light in equal^ stromj con-
centration within the tissue of the spotige about just as quickly
as in water ; hut in equal, weak concentration in the sponge less
quickly than in water. From this we may also deduce (p. 77)
that the feeding milieu for the alga is in fact not more favour-
ahle in the sponge than in the water, but about just as favourable
or even less favourable. That it is not more favourable, also very
clearly show^s from the fact, that the algae multiply in darkness
less quickly within the sponge tissue than in water (Table 10,
cnf. Table 6, col. 2 and Table 4 B, col. 4).

It is a matter of course that the above proved fact about the
protection, which a sponge in light gives to its algae, does not
lose anything of its validity, now that we have shown that the
greater intensity of multiplication in water, which occurs in
these experiments, is not explained by the milieu but simply by
the concentration-differences of the algae (see note p. 78).

But what about that protection (p. 78) in darkness? It appears
from Table 10, col. 3, and also by comparing Table 4 B and 8
that — contrary to the result in light — the algae in darkness
are in much less favourable conditions in the sponge than in the
water; in the sponge all algae are destroyed within short (p. 70).

As final conclusion ') we may give this one: In darkness the

1) In fact we should have stated this not only by comparing the behaviour of algae
when cultivated in water from the conduit and in sponges in water from the coiiduit,
but also by comparing their behaviour in lake water and in sponges in lake water.
This, however, is impossible, as we can cultivate sponges only in pure streaming water
(p. 9), and as, raoreover, ihe factor of import cannot be escluded in experiments in
lake water (p. 11). Bul in any case we know that the feeding milieu is less favourable
to the algae in lake water than in that from conduit (p. 82), and that in light the
algae are also in less favourable total-conditions in lake water (than in that from
conduit) (Table 10, col. 3). From which perhaps might follow that in light the de-
struction of the algae in lake water is about just as large as ia that from conduit,
at least is not weaker.

84

y^symhiotic^' association of Sjjongillides and ahja offers much less
advantage to the alga than a life f ree in the water, as in the sp'onge
all algae are destroyed. In light, on the contrary^ that „symbiotic"
association offers more advantage to the alga than a life free in
the water; hut that . advantage only consists in the f act, that the
sponge protects the alga against destruction, hy enemies for in-
stance. The milieu — the feeding milieu — , on the contrary, is
in the sponge not at all more favourahle to the alga than in the
water, neither i?i Ught nor in darkness, hut about just as favour-
ahle or even less favourahle. When further tve knoiv, that also in
Ught algae are constantly destroyed i^i the sponge — though less
than in the tvater — we must conclude, that from the point of
view of the use to the alga that association with the sponge cannot
he called at all a symhiosis in the meaning of that of the Lichetis.
In Ught the alga, so to say, has chosen the least of two evlls ;
ene cannot say more.

|3.

We have noiv come to the still more complicate question of the
use of the „symhiotic^^ association to the sponge.

I will begin with mentioning all the facts regarding this question.
After that we shall see, if all these different data can be united
into one conception.

1. On p. 25 I have mentioned already that the green sym-
biotic algae of the Spongillidae lodge oildrops, which they form,
as p. 20 shows, by photosynthesis.

2. The colourless algae may also show oildrops (p. 36) ; but
in general not so often as the green algae; while of these co-
lourless ones those, which kept their internal structure, show
them more often than the colourless ones, the structure of which
has got lost. This may appcar from the following analyses of
green Spongillae taken from the light, by. which the number of
algae with oildroplets is given per 100 algae which have been
tested.

85

<u

<B

01

O)

Q>

bc

bD

bC

bc

bC

u

a

a

a

a

a

ÖC

o

o

o

o

o

05

o.

o.

o.

a,

o.

1/3

co

M

»3

co

s

^

T3

T3

X

ï»

75

Li

rt

-th

<s

CO

. -^I

lÖ

pei- 100 green algae

72

60

80

94

74

70

„ ,, colourless ones with structure

30

22

40

40

;w

32.4

„ „ „ „without „

18

4

10

10

6

9.6

With a view to what we shall treat later on, I want to add,
tliat here almost exclusively algae were examined, which were
situated free in the protoplasm of the lodging amoebocytes, so
not in vacuoles.

3. Also in the amoebocytes of green sponges, so in amoebocytes
overladen with green algae, there occur numbers of refractive
oildrops lying free in the protoplasm; eee Table 12 and 13. They
are not stained by I in I K sol., but they become red with sudan
III in alcohol and gray-black with osmic acid (see note p. 25),
and are blue-green, when not stained and the microscope is well
adjusted — just as the oildroplets of the algae. They also have
the same diameter (0.4 — 1 /y.) as these ones, although the larger
specimina seem to occur more in the algae than in the amoebo-
cytes. Further the oildroplets of the amoebocytes very often
seem to be still much more refractive and sharper outlined than
those of the algae. This might show, that the oildroplets from
alga and amoebocyte are not identical.

Next I want to mention that, although these „oildroplets"
(of alga and sponge) will consist for the greater part of oil,
one still has to consider the possibility, that they might possess some-
thing as a plasmic stroma or cover, as is also given for instance
for the milk-globules. Also the above mentioned (p. 26) colouring
of the oil-droplets by haematoxyline makes us think of that.

4. How often I have paid attention to it, I have never been
able to see the slightest tracé of an oildroplet being ejected by
the symbiotic algae. Also the supposition, that such a phenomenon
miglit be possible, does not sound very likely — for we have

86

found a cell-wall round the alga (p. 26), and even without that
it is very unlikely already — . Still I have obtained a number
of observations with cultures of isolated green algae, from which
seems to follow that sometimes the number of oildroplets, which
occur outside the algae c. q. free in the membrane at the bottom
of the culture, rises and lowers with the number of oildroplets
within the algae, that is to say with the number of algae lodging
such a droplet. See Table 11.

In general, namely, the free oildroplets seem to disappear very
soon from an algal-culture. Quite intelligible, for instance by the
action of bacteria. Further it appears, that these free droplets
can only be numerous if there are also numbers of algae con-
taining an oildrop; if the number of the latter lowers — which
always happens when the algae are vigorously dividing — that
of the former seems to necessarily follow immediately. Is the
reverse the case (with rising, namely), this need not absolutely
take place. Sometimes however this happens in quite a striking
way. I will give an example: A culture in light of numerous
green algae, several of which carry an oildroplet, very rarely
shows a free oildroplet. After 10 days the number of green algae
with oildroplets has increased very considerably, the number
of free oildroplets also to rather a great number. Two cultures
are made then out of this one, and one of them is placed in
light under favourable, the other under unfavourable conditions.
After two weeks again the first culture shows a particularly high
number of green stages of division of the algae, consequently a
small number of algae with oildroplet, and also a small number
of free oildroplets; the 2^^ culture on the contrary contains no
stages of division , numerous algae with oildroplet and rather
a great number of free oildroplets. Now follow the first of these
two cultures. After a month this one shows very seldom a stage
of division and consequently a great number of algae with oil-
droplet ; yet free oildroplets are only present sporadical ; but three
months later, when dividing-stages lack and thus oildroplets still
appear in a great number of algae, the free oildroplets have be-
come rather numerous again.

87

By these observations one will acknowledge, tliat tliore seems
td" be some relation between the number of' oildroplets inside and
outside the green algae. What relation — in the experiments under
consideration — is not yet quite clear to me. I consider direct
ejection of the oildroplets by the algae to be excluded, not only
because of what I mentioned above, but even more because of
what I am going to say (5). I believe, that this relation is
more likely to be in the stages of „solution" of the algae,
the colourless ones with and without structure, about which I
spoke on p. 42 and 43. There are also some indications for it in
Table 11.

5. Also in the amoebocytes of colourless sponges, so in amoe-
bocytes with but few green algae, there are humbers of oildroplets
in the protoplasm. In Spongilla their average number in these
amoebocytes of colourless specimina from darkness is even some-
what higher than in the amoebocytes of green sponges from the
light, i. e. than in amoebocytes filled with green algae (in which
the oildroplets are formed). See Table 12. From this follows that,
very likely, there is no question at all about ejecting of oil-
droplets (or their constituent parts) by the green algae; for if
this were really the case, the amoebocytes of green sponges from
light had to contain ever so many more oildroplets than those of
colourless sponges from dark, while on the contrary the latter
appeared to lodge even more than the former.

Perhaps one might be inclined to explain this last fact as being
caused by a larger consumption of the oildroplets in a green
sponge in light than in a sponge in dark. In the first place I
have to answer then that, as the amoebocytes are exactly the
cells in which the green algae are especially to be found within
the sponge body (p. 16) — which cells therefore may be con-
sidered as being the place of production of the oildroplets — at
any rate at least in them there should still be something to be
seen of that larger production in green sponges in light. And in
the 2nd place it would be a mere chance, that this supposed
increased consumption of oildroplets in a green sponge in light
should exactly counterbalance the ever so much larger produc-

88

tion (which is not at all under the control of the sponge). Besides,
what might be the reason for that larger consumption? Perhaps
this reminds of the fact mentioned on p. 53, that green Spon-
gillae in light often prove to grow much quicker than colourless
ones in darkness. But growth is always only a consequence
of, among others, the quantity of food disposable; in other
words: if really the lesser growth of the colourless sponges were
the consequence of the smaller quantity of oildroplets they can
dispose of, it would be a very singular fact that there is still
rather a large number of those oildroplets left in the amoebocytes
of such a colourless sponge, that there is even more left than in
a green sponge in light! Besides, an organism especially wants
protein to grow and not so much fat (or carbohydrates). Last not
least, I have to propose another question, much more important,
in case one sticks to the opinion, that the oildroplets really get
directly from the green algae into the amoebocytes ; this question
namely, how ^ — if this supposition were right — the very few
green algae, which are present in a colourless sponge in darkness
(or twilight), could possibly procure all those oildroplets, which
we find in the amoebocytes of that sponge ; while, moreover,
those algae can hardly photosynthesise there, even will have to
die very soon (p. 70). Consequently these few green algae almost
exclusively dispose of the oildroplets, which they already carried
when imported from the outside to within the sponge, and
which in dark they are certainly not going to give immediately
to its tissues! As we are thus obliged to find for the colourless
sponge another explanation for the presence of oildroplets in the
amoebocytes, the suggestion is very likely, that this (other) ex-
planation will also prove to go for the green sponge. Besides,
the whole supposition of oildroplets being ejected by the green
algae by itself sounds rather unlikely, as I stated already above
under point 4.

But lateron I will mention quite another, much more logical
way, in which the amoebocytes do get really their oildroplets
from the algae (p. 98 — 99).

All that is stated sub 5 about ejecting oildroplets by the green

89

algae counts as mucli, without any, change, for ejecting (dissol ved)
carbohydrates, from whicli one miglit think the oildroplets ori-
ginating. I shall return to this lateron (11 — 13).

(). From the same Table 12 it also appears, that in the amoe-
bocytes of Spongillae the number of oildroplets in young tissue —
the branch-tops (p. 16) — is a trifle smaller than in full-grown
tissue — the branch-bascs — ; that it is however at its largest in
young, old and newly germinated gemnmlae, but that it strongly
diminishes in the stages of development which follow. Consequently,
the oildroplets seem to be consumed by the tissue of germinated
gemmulae.

7. While on the one side it appears from Table 12 that the
number of oildroplets in the amoebocytes is not in correlation
witli the number of green algae carrying an oildroplet — as
shown above under 5 — , on the other side we can eonclude from
the same table that apparently that number of oildroplets (in
amoebocytes) is in some correlation with the number of colourless
algae without structure, so with the number of dead algae, in
the sponge tissue. This would all at once explain the queer fact,
mentioned under 5, that in the amoebocytes of colourless sponges
from darkness there are somewhat more oildroplets than in those
of green ones from light; for we know (p. 59), and it appears
again from this Table 12, that in a sponge in darkness there
are more green algae dying than in light. But also the facts
mentioned under (> could be explained in connection with this:
in the course of the development of a sponge the total number
of dead algae is constantly increasing, according to p. 57, with
a considerable decrease in (or shortly after) the gemmule-stage
(this also appears in Table 12); so the same should happen to
the number of oildroplets per amoebocyte.

Which, however, is the right connection between the number
of oildroplets in the amoebocytes and the dying of the green
algae, why this connection must necessarily exist, can only be
treated lateron, when I have mentioned all facts concerning it.

8. In the sponge-tissue occurs a lipase, a fat-splitting enzyme.
In Table 13 one finds, how .1 have pointed out its presence.

9Ü

9. The uildroplets appear to bc more numerous in the choano-
cytes, the collar-cells lining the flagellated chambers, than in the
amoebocytes. See Table 14. Perhaps this might make one suggest,
that all oildroplets in the sponge have been taken from the sur-
rounding water by means of the choanocytes, the food-capturers
par excellence. This suggestion was the more justified, because
my sponges were mostly gathered in a by-channel of the lake,
along which were numbers of houses which emptied their refuse
from the drain-pipes in that canal ; even so, that the sponges were
often in the middle of the dirt. This supposition, however, proved
untenable; for the sponges gathered in the lake itself, in very
clean water — far from houses — , contained about as many oil-
droplets in their choanocytes as those which had grown in the
dirty canal water; while this also appeared to count for sponges
which had been cultivated for some time in flowing water from
the conduit (while no reduction occurred). See Table 14.

10. As we saw above under 7, that the number of oil-droplets
in the amoebocytes was in some relation with the number of
colourless algae, we might also expect here for the choanocytes
some relation between the number of their oil-droplets and that
of their colourless algae, That proves however not to be the case,
as foUows from this table:

choanocytic layer

green sponge

colourless sponge

number of

number of

oildrops

colourless algae

oildrops

rutlier numerous

several

some

some

»
few

mass

rather numerous

several

colourless algae

few

several

rather numerous

11. I have already mentioned on p. 25, that I have never
been able to show any carbohydrate within the symbiotic algae
— except the cell-wall, which of. course will consist of cellu-

91

lose. However, carbohydrato (glucose) will probably be furmed
(but theii kept in solution); so also Oltmanns (47) gives for
some algao that, although oil may bc found as final product,
tlic prime products of photosynthesis are probably carbohydrates;
also see Pfeffer (47 a) for plants in general.

13. The amoebocytes of green and colourless Spoiigillidae and
their gcmmules show, when stained by I in KI sol., numbers
of very sniall red-brown globules, much smaller than the oil-
droplets (Table 14) and especially situated along (the inside of) the
wall. On the other hand I have never found vacuoles stained by
I in the amoebocytes, as Lankester (35) states. One will be
inclined now to consider these small brown globules as a solid
carbohydrate ; but such a colouring by I does not yet give suffi-
ciënt proof by itself. So I have also tried to prove in a more
direct way, that carbohydrates occur in the sponge tissue. And
such with the help of tlie Fehling solution which, as known,
gives a red precipitation, when boiled with a reducing sugar (for
instance glucose or an other monosaccharide).

I rubbed a green Spongilla, just boiled the remaining fluid and
filtered it, while the symbiotic algae and all smaller particles
passed through the filter. The fluid reacted neutrally and was
light-green, rather troubled. This liquid, now, showed after having
been boiled with some Fehling solution rather a considerable
red precipitation, while a blind experiment (Fehling boiled
without sponge liquid) did not show any reduction. So sugar
(probably a monosaccharide) was present in the sponge. Next the
same was repeated with sponge liquid, which had in advance
been boiled for one hour with some drops of strong HCl
(to break down polysaccharides which might be present), then
neutralised by KOH and filtered; this liquid showed strenger
Fehling reduction than the original one. From this we may con-
clude, that the sponge liquid, consequently the sponge tissue, con-
tained a polysaccharide besides the monosaccharide. But this poly-
saccharide need not exactly have been the carbohydrate which can
be stained by I; it may have been exclusively the cellulose of
the algal cell-walls (perhaps the increased reduction after hydro-

92

lysis by HCl might also been explained as caused by the carbo-
hydrates originating from the nucleins?).

The same result, however, was obtained also for the gemmules
after I had almost entirely freed their rubbed material of (coarser)
solid particles (among others of algae and oil-droplets) by centri-
fuging and extracting with ether. Moreover, the living cells of
the gemmules considerably swell in water, so apparently possess
a strongly hypertonic cell-fluid, which corresponds very well with
the presence of dissolved sugars.

So we may conclude, that a polysaccharide is present in the
sponge-tissue also beyond the (coarser) solid parts of the cells;
we now can freely explain the above mentioned small globules
stainable brown by I as consisting of the polysaccharide in question.

13. As appears from Table 14, these small globules are present
in about the same number in amoebocytes of a green sponge in
light, so in amoebocytes filled up with green algae, as in those
of a colourless sponge from darkness, so with but few green
algae; it may even be, that these globules are somewhat more
numerous in the second than in the first cells. From this we
may conclude again, that export of carbohydrates from the green
algae probably does not take place at all. For if it were the case,
these carbohydrates in solution — in 11 namely it appeared, that
these will be present in the algae — , which would then evi-
dently be deposited in the sponge tissue partly in the form of
reserve food (the little globules), had at any rate to be much
more numerous in the green sponge from light than in the colour-
less one from darkness, while exactly the reverse proved to be
the case.

Perhaps one might be inclined to explain this last fact, just
as in 5 for the oildroplets, as being caused by a larger con-
sumption of the carbohydrates in a green sponge in light. I then
can give exactly the same answer, I have given already (in 5)
for the oildroplets, and which I am not going to repeat.

As we saw that the little globules, which can be stained by
I, in the amoebocytes of a colourless sponge from darkness are
probably even somewhat more numerous than in those of green

9:5

ones from light, it is probablc — in analogy with wliat was
stated above under 7 for the oildroplets in amoebocytes — that
there must be some direct relation between the number of these
little globules and the number of dead algae, which, as known, is
also larger in sponges in darkness than in sponges in light (p. 59).
I shall mention only lateron, what relation this is.

14. The little globules stainable by I are to be found somewhat
more numerous in the choanocytes of the flagellated chambers
than in the amoebocytes (Table 14). Also here one could ask
the question, which we put above in ï) for the oildroplets, if
perhaps not all these globules could have been captured from the
surrounding water by the sponge with the help of its choanocytes.
But also this question we must answer negatively, as these glo-
bules are about as numerous — or only a little less numerous —
in the choanocytes of sponges out of the lake-water or the water
from the conduit as in those of the sponges from the dirty canal
water (Table 14).

15. As we saw under 13 that in the amoebocytes there is
some relation between the number of globules, stainable by I and
the number of dead algae, we might expect the same relation
in the choanocytes. This proves, however, not to be the case, as
the table below shows.

choanocytic layer

green sponge

colourless sponge

number of
glob. st. by I

colourless algae

number of
glob. st. by I

colourless algae

numerous
mass
»

few
some

»

mass

»
»

few

several

rather numerous

16. On p. 18 — 20 I have proved already, that the green sym-
biotic algae produce 0^ in light.

94

17. In the amoebocytes of the Spongillidae food vacuoles are
to be foiind including symbiotic algae in different stages of di-
gestion ; so one finds in these vacuoles all normal and „solution"
stages of those algae, which I treated repeatedly (p. 42 — 45),
viz. : green ones, colourless ones with clear structure, with a shade
of structure, without structure, and vague shades of colourless algae.
Besides these symbiotic algae one also finds in the vacuoles:
diatoms, ordinary algae, bacteria, all sorts of unrecognisable de-
tritus and the above mentioned oildroplets, mutually combined as
well as with the symbiotic algae.

18. In sponges newly caught from nature these food vacuoles
are rather rare in the tissues (Table 15). Consequently, the
sponge in free nature seems to digest only few symbiotic algae
and other food particles in this way by vacuoles.

19. In sponges, which have been for some time in aquaria (with
water from the conduit) these food-vacuoles, however, are more
numerous (but there does not seem to be much dilference then
between cultures in the light and in the dark; Table 15); so
under these circumstances the sponge proves to digest more food
in this way.

20. In newly caught Spongillae food vacuoles are less numerous
in young tissue (branch-tops) than in fuU-grown (branch-bases)
(Table 15).

21. In newly caught Spongillae the food vacuoles are somewhat
more numerous in the tissues of colourless specimina from dark-
ness than in those of green ones from light ; they seem equally
numerous in Ephydatiae (Table 15).

22. As I mentioned already on p. 42 — 43, most of, not only the
normal green symbiotic algae but also of the often mentioned
colourless dying- and „solution"-stages of those algae (p. 42 — 45),
occur quite free in the protoplasm of the amoebocytes, not in
food vacuoles.

23. The amoebocytes with (green or colourless) symbiotic algae
form — as was partly mentioned on p. 16 — the greater majo-
rity of the cells of the green and the colourless sponges. The

95

amocbocytes of green sponges lodge, besides tlieir nuineruus green
algae, mostly also one or more colourless algae free in their pro-
toplasm ; while, after what was said above, it stands to reason
that also the amoebocytes of colourless sponges contain colourless
algae free in their protoplasin.

24-. In green and colourless sponges the amoebocytes appear to
lodge more colourless symbiotic algae than foreign enclosures
(unicellular algae, etc). The same thing counts for the whole
sponge-tissue.

25. Particles, which have been taken up by amoebocytes, never
come immediately in a vacuole but remain free in the protoplasm ;
if a vacuole is formed around, this only happens lateron.

26. From ïable 8 it appears, that in green sponges cultivated
in water from the conduit the number of colourless algae with
structure generally also increases in the light.

Now that we have described in the above given 26 points the
chief facts, irhich bear upon the question aboiit the use of the
symbiotic association to the sponge^ we tvill now see, if all these
various data caii be united into one conception; in other ivords^
if we can come to an answer to this question with the help of
these data. Probably one will suppose already oneself in which
direction the conclusion can be found, by the way in which now
the 26 points have been arranged. I must confess, however, that
this solution has troubled me a great deal; while on one point
it requires still further completion.

As was mentioned under point 17 and 18, the fresh-water sponge
seems to digest free in nature only little nutrition (symbiotic
algae and other food particles) by means of food-vacuoles. So
the sponge must evidently supply its food ii; another way. Several
ways are imaginable:

First the possibility, that the sponge lives of organic materials
in solution, present in the lake water. I ani not going to treat

96

here the question, if this supposition — the Putter theory (48,
49) — should also count more or less for the Spongillidae ; for
these sponges possess, as we will see presently, another very rich
source of food ; so that the argument, on which Pütter's theory
is based, seems not to hold good for the fresh-water sponges.
The dissolved organic materlals of the lake water are for them
surely not the most important source of food.

Next one might have thought, that it were the products of
photosynthesis of the green symbiotic algae (the oildroplets and
carbohydrates) which, after having been ejected by the algae, would
serve the sponges as food (point 1, 3, 11, 12). We now know^ how-
ever (point 5, 13), that it is very likely such an eject'mg of oil-
droplets and carbohydrates by the algae does not take place at all.

There is still another possibility, viz. that the sponge is fed by
proteins (or their constituent parts) which the green algae could
eject. For the (colloidal) proteins this sounds, however, very un-
likely ; and also for their parts, the amino acids, will be no
question about ejecting by the algae, as we saw above that it is,
very likely, already not the case for the primary products of pho-
tosynthesis (the carbohydrates), that are still much more numerous.
Consequently, nor in this way we escape from the difficulty.

The solution is, that according to point 22 — 24 (p>. 94 — 95)
the sponge has a very important, almost inexhaustable, perhaps even
its principle source of food in the green symbiotic algae, which con-
tinually die (p. 46' — 48, 57) free in the protoplasm of its amoebocytes,
and ivhich then pass there gradually from „colourless algae ivith clear
structure'''' into the successive „solution stages'\ „colourless ones with
shade of structure'''', „colourless ones tvithout structure", and „vague
shades of colourless algae", in order to finally disappear entirely
(p. 42 — 45). Consequently, here free in the protoplasm of the amoe-
bocytes necessarily an — dlthough rather slow (p. 57),nevertheless —
complete break-down and solution takes place of the substances the
symbiotic algae consist of; ivhile the products of the decomposition
must come to the disposal of the amoebocytes. How this decom-
position is produced, I cannot yet decide ; but it is evident, that
enzymes of the amoebocytes will take part in it.

97

So it seems, as if the sponge wonld dispose of two different
methods of digestion, l^i the often appearing sloiv digestion free in
the protojdasm of the amoehocytes, 2nd the less common quicJcer
digestion in food vacuoles of the sam,e cells. But is it not more
likely, tliat these two methods are only apparently diiïerent and
not really? With a slow digestion only littlc enzyme will be
secreted to the body which must be digested, so no vacuole- will
be formed around ; with a quick digestion on the contrary much
enzyme, consequently a vacuole is formed. The whole difference
between vacuole digestion and digestion free in the protoplasm
would thus only be founded on a difference in the rapidity, with
which the amoebocyte desires to digest a body (see also chapt. U).
With a normal regular course of the process of life there is no
need for a quick digestion, ouly little enzyme is secreted, conse-
quently no food vacuoles are formed.

But if, for instance, a sponge is taken from its habitat to an-
other place, eg. an aquarium with water from the conduit, where
it will miss at any rate all kinds of nourishment — if not
the symbiotic algae, yet many other materials (dissolved in lake
water?) which probably are not less important — it is very
likely, that the sponge will theu try to supersede its lack of other
materials by a quicker digestion of the food, which is at its dis-
posal; in other words, the sponge will be going to secrete more
enzyme and form thus vacuoles round its food. Now, according
to point 19, exactly this thing happens with sponges in aquaria !
Next the fact, that in newly caught Spongillae, according
to point 20, the food in young tissue is less quickly digested
than in full-grown ; it can be explained in several ways. But it
is not clear at once why, according to point 21, a quicker digestion
takes place in the tissues of colourless Spongillae in darkness (not
of Ephydatiae!) than in those of green ones in the light; for
there is probably no question at all about a stronger nutrition
of the green sponge . from the side of its green algae (p. 96),
while in the colourless sponge even some more algae are digested
in the protoplasm than in the green one (p. 96, 59, 46 — 48). So
one must come to the conclusion, that the colourless Spongilla

98

wants more food tlian the green — once more, this cannot have
its cause directly in the algal products of photosynthesis — but
in what then ? Perhaps the following solution holds good :

In connection with what was mentioned in point 16 (p. 93),
one must admit, that the green sponge in the light disposes of a
very considerable abiindance of Oo in its tissues, which the (colour-
less) sponge in the dark cannot have, of course. It is now
acknowledged in general physiology, that the katabolic phase of
metabolism has quite another course in lack of O.^ than in abun-
dance; in lack of 0^ a much more largely, but much less deeply
extending break-down of body-materials (proteins, carbohydrates)
takes place than with sufficiënt O.^ — Verworn (58), Hermann
(28), Hammarsten (26), Biedermann (6), De Vries (63) — ;
indeed, in lack of 0.^ much more material is required for obtaining
a certain quantity of energy, as the organism for source of energy
is then chiefly dependent on not oxidative splittings which procure
but little energy, while then, also by the faulty oxidation, a great
deal of the chemical energy of the splitting-products is lost for
the organism. In this way one would be inclined to explain the
fact, that the colourless Spongilla in darkness wants more food
than the green one in the light '). For the present this is but
a suggestion, to which I shall return however later on,

Now that we have seen that the freshwater sponges for a great
deal, perhaps even chiefly, find their food in the symbiotic algae,
which continually die and are digested and dissolved free in the
protoplasm of their amoebocytes, the connection, which there is
according to point 7 (p. 89) between the number of oildroplets
in the amoebocytes (point 3) on the one side and the number of
dead (colourless) algae in the sponge tissue on the other side,
may be explained quite simply. For the sponge tissue disposes
of a lipase (point 8), and in point 1, 2 (p. 84) we found
an always decreasing percent of algae with an oildroplet.

1) That this seemed not to be the case with Ephydatia, might be explained from the
fact, that the colourless specimina I exarained, which contaiu always soine green algae,
were partiy originating from the light.

99

according as tlic digestion of tlie algao had progressed. So in
other words, just as the amoehocyte sloivly digests the other constituent
jyarts of the algal cell and makes use of their decomposition-pro-
ducts, in the saine iray and at the same time it also digests the
olldroplets of the algae, and ivith their products of spUtting (the
glycerine and acid) huilds up its own oildroplets. Indeed, we saw
(point 3), that very likely the oikiroplets of alga and amoebocyte
are not identical!

From the preceding follows, that we may consider the pro-
duction of the splitting-products of the oildroplets (the glycerine
and acid) — so probably also the production of the oildroplets
themselves (see below) — in the amoebocytes to be direct pro-
portional to the number of the algae being digested, in other
words, to the sum of the number of colourless algae with and of
that without structure.

The same thing will count also for the production of the carho-
hydrate globules, which can be stained broiim by 7; as source of
the carbohydrate we must of course accept — there are no such
globules in the algae (point 11) — either the dissolved carbo-
hydrates and the wall celluloses, or the nucleins, or again the oil-
droplets of the algae. (The transmutation of fats into carbohydrates,
as well as the reverse, we repeatedly meet in physiology.)

According to point 9, 10, 14 and 15 the oildroplets and the
globules, stainable by I, are even more numerous in the choauo-
cytes than in the amoebocytes. From those same points it also
appeared, that these oildroplets and globules are not captured
from the surrounding water by the choanocytes, and that there
is no relation between the number of oildroplets or globules
and the number of dead algae in the choanocytes. Therefore it is
very likely, that these oildroplets and globules are carried on
from the amoebocytes through the „intercellular groundsubstance"
to the choanocytes; for the amoebocytes with their constant di-
gestion of algae form, as we saw, the true place of production of
those corpuscles. But why are these carried on to the choanocytes
in such a great number, that they-are even more numerous there
than in the amoebocytes?

100

On p. 50 I have treated alroady, what an enormous quan-
tity of water a tiny sponge makes circulate through its canal-
system. This eurrent of water is kept iip by the flagellar-motion
of the choanocytes. Consequently in these choanocytes a very
strong transformation of energy takes place ; those choanocytes ^
therefore, must necessarily dispose of a great source of energy.
What is more evident than fhat this large mass of oildroplets and
of carhohydrate globules woidd serve as such! The more so, as
we know from genera! physiology, that in organisms labour,
the so called functional metabolism, exactly takes place at the
expense of N-free materials, so of carbohydrates and fats —
Verworn (58), Hammarsten (26).

Next we can say that it is also very likely, that the oil-
droplets (and carhohydrate globules?) are used in great numbers
for the development of the gemmules ; for what we have given
an argument above.

Let us just look over, what we have stated in the last pages
about the production and the consumption of fat in the sponge ;
and let us try to make up in this way an explanation of the facts,
which we derived from Table 12 for colourless sponges from
darkness and green ones from light (point 5, 6, p. 87 — 89).

This must be preceded however by another question. Namely :
does the great mass of fat, obtained by the sponge from the
digestion of the algae, occur in the sponge as oildroplets — the
number of which we can easily state by means of the micros-
cope — , or divided into glycerine and acid — which entirely
disappear from observation ? In other words : may we see in the
number of oildroplets, which has been experimentally stated, the
total quantity of fat present in the sponge tissues, or, if not
the entire, yet a proportional quantity — or may we not do
so at all? This is an important question. The (l^t and) 2"'^ sup-
position sounds most probable; not the S'*!. This question will
soon find its solution in the foUowing.

Now return to our subject. We were going to try to make
up an explanation of the facts mentioned under point 5 and 6,
with the help of the data about production and consumption of

101

fat in the sponge. Our data are (calculated per unit of time
and of sponge-volume) :

r. The production of fat (p) is always proportional to the number
of colourless algae in the sponge (pag. 99). We know this number
of algae in the different stages of development of the tissue of
green Spongillae from light and colourless ones from darkness,
from Table 6, pag. 46 — 48 ; so we can imraediately fix the course
of p: p will increase in green and colourless sponges during
the development from very young to full-grown tissue, and
in colourless sponges it will always increase more than in green
ones; at the end of, or shortly after, the gemmule-stage p will
decrease considerably and be about the same in green and
colourless sponges.

The consumption of fat is determined by the motion of the
flagella in the chambers (/") and by the development of the gem-
mules {g). From this follows:

2. The consumption (ƒ) is proportional to the number of fla-
gellated chambers (we suppose now, that the average of their
flagellar-motions is always equal), the number of which is zero
in gemmules, but quickly increases in very young tissue, to
remain constant afterwards; f does the same. Next — let us say
for simplicity's sake — f will be equal in green sponges in light
and in colourless ones in darkness.

3. The consumption (r/) is only present and then liigh in the
very young tissue during the development of the gemmules, and
the same in green and colourless sponges.

From these data follows: I. As p increases more during the
development of colourless sponge tissue than during that of green,
while (/■ + </) remains the same in both, there must be, l''* some-
what more fat in young (N.B. not very young!) tissue of colour-
less sponges than in that of green ones, 2'>'i in full-grown tissue
of colourless sponges much more fat than in that of green ones
(point i>, p. 87). II. Ist. As p increases during the development
of green and colourless sponge tissue while {f + g) remains
constant, the quantity of fat must increase in that period in both
sponges. 2°'!. As in both sponges p only considerably lowers at

102

the end of, or sliortly after, the gemmule-stage, but (/' + g) di-
minishes already immediately in that stage to about zero thé
quantity of fat must be very high (maximal) in that period.
3''<i As in both sponges j) is a minimum in very young tissue,
while here {f + g) reach their maximum, the quantity of fat must
lower considerably (be minimal) in that poriod (point 6, p. 89).

From this we see: l^t Hoiv perfectly the exjjerimentaUi/ statecl
facts about the quantiti/ of oildroplets, present in the sponge tis-
sues^ correspond ivith. the theoretical calculations of the quantity of
fat, which we could mahe from the co-operation of the factors
that proved to rule the producttoti and the consumption of fat in
the sponge. From this follows again: 2Qd That the quantity of oil-
droplets in the sponge tissue must be in fact proportional to the
total quantity of fat that is present (see p. 100).

Undoubtedly, such calculations cguld be made also for the
carbohydrates in the sponge tissue. I do not dispose, however, of
sufiicient facts to test their result. We might still conclude that
the fact mentioned under point 13 (p. 92), that the globules
which can be stained brown by I in the amoebocytes of colour-
less sponges are perhaps somewhat more numerous than in those
of green ones, will have to be explained in the same way as we
did here for the oildroplets.

At last the question : What is the reason of the dging of the
green symhiotic algae tvithin the amoebocytes? Probably one will
be inclined to see this in the fact, that the amoebocytes digest
the algae, as we saw above. Certainly, the amoebocytes are sure
to digest the dead algae, but have they also purposely killed all
of them — i. e. to make them serve as nutrition ? Or does the
sponge digest them, because (after) all (or some) algae were al-
ready dead for quite a different reason? Perhaps one considers
this at first sight as a singular and rather far fetched supposition.
After due consideration, however, one will acknowledge, that this
supposition is not at all so singular and far fetched ; on the con-
trary, that one certainly must consider this possibility too. For
the rest I will immediately adniit, that the whole question about

103

the reason of the dying of the algae is cspecially of thooretical
interest and not so much of practical, as indeed all dead algao
conie to the benefit of the nourishment of the sponge.

It is rather a complicate question, which I am going to treat
more in extenso.

I. In the first place we will answer the question, what causes
are tlieoretically possible for the dying of the green algae in the
amoebocytes, and at the same time if those causes should have
to behave differently in a sponge in light and in a sponge in
darkness : Ist Of course : the sponge cells might actively kill the
algae with the aim to digest them, so from want of food. Would
there be any reason then to accept, that this cause would be
active in light in another degree than in darkness ? Certainly !
One might expect, that the amoebocytes of a sponge in darkness
should kill the algae in a higher degree than those of a green
sponge in light. For some pages back (p, 97 — 98) we had several
sound reasons for supposing, that a sponge in darkness would
need more food than a green one in light. The more so, as we
saw on p. 100, that the sponges are very likely to transform
relatively great quantities of energy in the flagellar-motion of
their choanocytes, in which transformation in case of lack of 0.^
not only more N-free materials, but very likely also the proteins
themselves of the choanocytes are broken down and, consequently,
must be restituted (p. 98). As 2ad cause of the dying of the
green algae in the sponge cells comes into consideration : „poi-
soning" — so to say — of the algae by products of metabolism
of the sponge, so without any relation to the want of food and
the nourishment-process but, for instance, more as a reaction of
defence of the sponge against a foreign intruder. There is no
certain proof for this possibility, but some indication in the
direction of poisoning of the algae by products of metabolism
can be the behaviour of isolated green sponge-algae, when there
appears in their culture a strong infection of diatoms, mould, or
ordinary green algae. For, as I have mentioned already on p. 43 and
45, -the sponge algae die under such cirQumstances. (On the other
hand the cultures — which, as mentioned before, succeeded well —

104

of green sponge algae iu liquid from a pressed sponge (Table 4),
cannot teil against this possibility of poisoning ; for constant pre-
sence of those hurtful products of metabolism might always be
connected with the life of the sponge ; though then, of course,
they cannot be present in great quantity ; what is however not
necessary here.) Is there, finally, any reason to suppose, that this
„poisonous" influence of the prodncts of metabolism is larger or
smaller in a sponge in the light than in the dark? This „poison-
ous" influence taken by itself does not give way to answer the
question affirmatively ; but if one considers it as a reaction of
defence of the sponge against an intruder, then there is a reason
to suppose, at least to think it possible, that this influence is
strenger in darkness than in light. For the following reason :
As we shall see on p. 109 — 112, the production of 0^ by the
green alga ia light is in fact the only function of life of the
alga, in which the sponge can have any direct interest. Of course
this function is stopped in the dark, and then the sponge has no
interest in the life of the alga any more, but probably will have
a reason to fight against it as a foreign intruder, and such more
vigorously than 'it would have done in light. x4.s 3i'd cause for
the dying of the algae in the sponge cells comes into considera-
tion : lack of food, and as 4th cause : lack of 0.^ and accumulation
of C O2 in the algae themselves ; all of them only for algae in
sponges in darkness, of course.

II. Let us now recall to our memory, what facts we have got
to know successively about the dying of the green sponge-algae.

1. Continually algae are dying in the sponge tissue (p. 56 — 57).

2. The intensity of the dying in all stages of development of
the tissue is constant, with a considerable lowering however in
the gemmule stage (p. 57). 3, Of the same number much more
algae die in a sponge in darkness than in light (p. 60). 4. The
intensity of dying in light is about equally high in a weak con-
centration of the algae in the sponge tissue as in a strong con-
centration ; in the dark, on the contrary, smaller in the first case
p. 61). 5. In free nature the number of dying algae (colour-
less ones with structure, p. 56) is always very small in a green

105

sponge in light witli regard to the total nurnber of living (green)
algae present (p. 46 — 48, ïable 6). 6. In nature the number of
dying algae (colourless ones with structure) in a colourless sponge
in darkness is larger than iii the green sponge in light (p. 48) ;
this number (in colourless sponge) is almost equal to that, which
is continually imported into the sponge (p. 69 — 70). 7. If one culti-
vates green sponges in light in water from the conduit, the number
of colourless algae with structure generally appears to increase
(p. 95, point 36). 8. Isolated and cultivated in cultures, the algae
prove to remain living and green for months in light and in
darkness, and even to multiply (p. 40 — 41).

Let us now see, to what conclusion regarding the cause of the
dying of the algae within the sponge ■ — point I, 1 — 4- (p. 103 —
104) — we can come in connection with the facts, mentioned
here under II, 1 — 8. And let us then begin with the dying in
a sponge in darkness.

As we see on the one side (point II, 5), that only so few
green algae die in a sponge in light and on the other hand
(point II, 3, (>) so many more in a sponge in darkness, we must
come to the conclusion, that in the last case the lack of light is
the reason of the so much increased mortality. So we immediately
try to find its cause : on the one side (point I, 1) in the sponge
cells killing the algae much more considerably from want of food
and (point I, 2) in the stronger „poisonous" influence of the
metabolism-products of the sponge in darkness, on the other hand
(point I, 3, 4) in lack of food and of 0^ and in accumulation
of C 0^ in the algae themselves. However, we also know (point
II, 8) that without the sponge tissues the algae can live for
months in darkness and even multiply. Consequently, that lack
of light — with its supposed consequence of lack of food and
of 0.^ and accumulation of C 0.^ in the algal cells — by itself
cannot possibly be the direct cause of the dying of the algae in
darkness. On the contrary, it proves necessary for that manifold
dying of the algae to be in darkness in an actively living sponge
(point II, 6, 3, 2, cf. Table 10). The only and at the same
time most general solution would be therefore, that on the one

106

side the weakened power of resistance of the algae — in conse-
quence of them being in the sponge in darkness, lacking food
and O2 and with accumulation of C 0^ — , on the other hand
the still stronger hurtfull influences from the side of the sponge
cells (point I, 1, 2) — also in consequence of them being in
darkness — are the causes, that such a great number of those
algae die in the amoebocytes in darkness.

Why only so few algae die (point II, 5) in a sponge in light
with regard to the total number present, is also quite clear after
the preceding. The power of resistance of the algae will be much
higher here, in light, than in darkness. The hurtful influences
from the side of the sponge, also by itself already less forcible
now, will thus destroy much fewer algae in this case than the
sponge, which remains in the dark. But there will still always
be a small number of algae, that disposes of less power of resist-
ance for some or other reason; this will have to be destroyed
by the sponge (compare II, 8).

Also the other facts mentioned sub II, 1 — 8 are very well
compatible with this solution.

At last we get to the question, what those hurtful influences
from the side of the amoebocytes, which proved able to kill the
living algae with weakened resistance, are exactly. Whether they
are: simply (point I, 1) a killing from want of food, so a certain
feeding-process of the sponge cells; or (point I, 2) a „poisoning"
of the algae by hurtful products of metabolism of those cells,
consequently something, which in fact would have nothing to do
with the direct feeding process of the amoebocytes, but for instance
should be more considered as a reaction of defence of the cells
against an intruder; or, as we have just formulated above, both
causes together. In all three the cases, however, the final result
remains the same, namely that the algae killed in one of the 3
ways are digested at last by the amoebocytes. So this question has
in fact not much practical use ; it is more of theoretical interest,
as I remarked above.

Also, no definite answer can be given for the present; there
are arguments for both points (I, 1 and I, 2). This can be shown

107

easiest in consequence of the fact (point II, 3, 5, (i), that the
green algae in a sponge in darkness die in such a great number,
in light on the contrary only in such a small. Against the
opinion, that stronger „killing from want of food", so the in-
creased want of food, in darkness (point I, 1) would be a
cause for the manifold dying, tells :

a. The fact that, as appears from ïable 8 and Table 15, several
of the (groen) sponges, which have become almost colourless in
dark, contain only few food vacuoles, so behave as if they did
not specially want food, as stated on p. 97 — 98 (see ni's 333, 334,
340, 344, 366^1, 366 II).

h. The fact, mentioned on p. 94 sub 19, that there are about
the same number of food vacuoles in green sponges after their
culture in aquaria in light as in darkness; in other words: that
the want of food would not be larger in sponges in darkness
than in those in light.

By these facts the chief argument, that „killing from want of
food" could in general be a cause for the dying of the green
algae in the amoebocytes (p. 106), would fall.

With a view to this we would do better to exclusively admit
as cause for the dying: „poisoning" of the algae by products of
metabolism present in the amoebocytes, stronger in the dark and
active in all cases wheu for some reason the power of resistance
of the algae has weakened (p. 103, point I, 2, p. 106).

On the other hand, however, there are even more and stronger
arguments which speak for the fact, that „killing from want of
food" (p. 103, point I, 1; p. 106) certainly must be a cause for the
dying of the algae in the sponge. I therefore refer to the points
II, 7 and 4. ïhat increase of the mortality of the algae, when
the green sponges are transported into water from the conduit (in
light) — where the sponges will have to miss many food ma-
terials, which they found in nature, so that they will have to
make up for it in some way or other (see p. 97) — shows
very much in the direction of „killing from want of food". But
point II, 4, the fact namely, that the mortality in weak con-
centration of the algae in the sponge in the light is equal to that

108

in strong concentration (per unit of sponge volume) can even
only be explained by this last cause for the dying. From this
would follow, that a sponge in light, whether it lodges many or
few green algae, wants one and the same number of these for
food. It is quite clear, why (II, -t) in a sponge in darkness the
mortality in weak algal concentration is less than in a strong
concentration : in darkness the mortality is much larger than in light ;
if however the concentration is weak, it is impossible that many
algae die. Why (II, 2) the mortality in all stages of development
of the tissue remains constant, could be explained by „killing'from
want of food" as well as by „poisoning by products of metabolism".

Finally there are arguments which show, that in sponges in
darkness there is certainly reason to speak of an increased want
of food — in consequence of lack of 0.^ — ; which vs^ould make
a strenger „killing of the algae to digest" from the side of the
sponge cells quite intelligible (p. 103, point I, I, p. 106):

X. The argument, mentioned on p. 97, that in colourless Spon-
gillae from darkness, examined when newly caught, the number
of food vacuoles appears to be greater than in green ones from
light (p. 94, point 21) ; which argument formed exactly the
starting point for the supposition about the changed katabolic
phase in lack of O2 (in this case = lack of light) (p. 98).

/3. When speaking about the growth of the sponges, I have
mentioned (p. 53) that one could generally state, that green
Spongillae (in light) are larger, so grow more quickly, than co-^
lourless ones (in darkness). What can be the reason? Very likely,
there is no question of a strenger nutrition of the green sponge
from the side of its green algae, while even somewhat more algae-
are digested in the colourless sponge than in the green one, as
mentioned on p. 97, Consequently, there is no question about,
that the difference in rapidity of growth is founded on a smaller
quantity of food, which the colourless sponge would have at its
disposal. But it will have to be founded on a greater want of
food, namely chiefly of proteins, in consequence of lack of suffi-
ciënt O., in tlie tissues of the colourless sponge in darkness
(p. 98, 103, I, 1 and p. 88).

109

When we look over the residta ohtaineJ, we migld conclude the
foUowing cmises for the dijing of the algae in the sponge tissue:
A. In light in fact only „killing froin want of food'^ (point 1,1^,
and such of the (few) algae, the poiver of resistance of tvhich is
somewhat weaketied already for some or other reason; but not
„poisoning" by products of metabolism (point I, 2) nor lack of
food, lack of 0.^, and accumulation of CO^ in the algae them-
selves (point I, 3, 4). B. In darkness either ^killing from want
of food^' (point I, \) — perhaps even stronger 7iow — or (and)
„poisoning''^ hg products of metabolism (as reaction of defence of
the sponge against a foreign intruder) (point I, 2^, and such
again of algae, the power of resistance of wkich has certainly
weakened noiv niifch more, in consequence of lack of food or of
0.^ and accwmulation of CO.^ (point I, 3, ■i).

For the present a more detailed conclusion cannot be given;
more data are required for that, among others about the problem
if there is really question about lack of 0^ — with all its con-
sequences, as for instance increased want of food — in the tis-
sues of a sponge in darkness.

Let us now pay attention to the two points {oc, (3, p. 108), re-
garding this last problem and which are so important, because
they give us an insight into the sigtiificance, which the 0^, se-
creted hg the green algae in light within the sponge tissue, might
have for the life of the spo?ige. One cannot say, that the con-
clusion, made in connection with those points o. and /3, quite
satisfies us.

The hypothesis, that in lack of 0.^ the kataholic phase of the
metabolism will have quite another course (than in abundance of
O.J and consequently will cause an increased want of food —
as is given on p. 98 and 103 sub I, 1 — may be right in general,
it seems a bit far-fetched to consider this hypothesis applicable
to our case of a sponge in darkness. Certainly, the sponge in
darkness will possess a much smaller quantity of 0.^ in its tis-
sues than the green sponge in light. But is there really lack of
0^, while sponges have even an extremely strong circulation of

110

water? Sliould one not rather suppose, that by this circulation
the necessary quantity of 0.^ will already be kept up sufficiently
in the tissues of the sponge in darkness, though it will be lower
than in the green sponge in light — perhaps the green sponge
in light wil not do anything with its larger quantity of 0^ and
simply let it slip — ? If this were not the case, liow would
then be the course of that katabolic phase in all higher water
organisms not lodging chlorophyll, when lack of light ah*eady
changed it so enormously in Spongillae (that is to say, made
it go on accompanied with freeing of but relatively little energy).
One then had to come to the conclusion, that all these higher
water organisms, not lodging chlorophyll, can only produce less
complete oxidations in their katabolic phase of metabolism (that
is to say, less complete than the green Spongillae in light).

On the ether side one has to acknowledge that it is diffi-
cult to imagine, that this large quantity of 0^, which is present
in the tissues of a green sponge iu light — I just remind that,
according to p. 18 «, green Spongillae in sunlight even develop
gasbubbles (very likely of O^) — would have no considerable
influence on the katabolic phase of metabolism of the sponge,
Besides, ^how would otherwise the phenomena, mentioned on p.
108^ /3, have to be explained? ')

But let us leave now this question about the lack of O2 (with
all its consequences) in the tissues of a sponge in darkness. It
cannot be dissolved before we have stated experimentally, if in
fact Spongillae in darkness excrete less complete oxidated products
of metabolism than green sponges in light. Certainly this question
would be worth such a research ! I hope to be able to do this
afterwards.

Also the question which was our starting point on p. 106,
namely : whicli in fact are the exact causes of the dying of the
algae in the amoebocytes, must, as said before, wait for its de-
cision. The best thing is that, for the present, we content our-

]) And how (sce p. 51 noto) the perhaps smaller „filtering power" of a (colourless)
sponge in dark?

111

selves witli the general fornmlatinfj- of the answer given on p. 109.

The final result of our research info the use of the y^sijmhiotic'''
associatmi (of sponge and yreen ah/a) f o the sponge is therefore:

It is either the want of food of the sponge — which might he
stronglg increased in darkness — or {and) the y^poisonous'''' influence
of harmful products of metabolisin of the sponge (fo he considered
as a reactioti of defence agaijist a foreign intruder) which
continuaUij destroys green symhiotic algae in the amoehocytes ;
atid exactly those algae, the power of resistance of which is already
'tveakened for some or other reason — for instance by having heen
in darkness — (p. 102 — 109). All algae killed in this way come
to the henefit of the nourishment of the sponge ; as this one digests
and dissolves them entirely either free in the protoplasm of its
amoehocytes or in food vacuoles, keeps the products of the decom~
position (p. 96 — 97) and rehuilds its own cell parts ivith them,,
naniely for instance the oildroplets and carhohydrate glohules
(p. 98 — 102). These oildroplets and carhohydrate glohules in their
turn are, among others, the source of the great quantity of energy,
which the sponge transforms in the fagellar mofion of its choano-
cytes (p. 100).

For the present no decision can he given ahout the exact signi-
ficance for the life of the sponge of the O.,, which the living green
algae in light secrete within its tissues (p. 93). It may he, that this
O., is of much significance ; even so much, that the katahoUc phase
of the process of metaholism in a green sponge in light has quite
another course hy it — namely gives a relatively much larger
quantity of energy to the sponge — than in the sponge in darkness
{p. 98, 103, 109 — 110). Some indications were found for this; hut
this important question requires quite a seperate research, before
anything can he said for certain.

As we saw {p. 96, 87, 92) it is very likely, that direct transfer
of products of photosynthesis from the living green algae into
the sponge tissue does not take place at all.

When next we ask, whaf in fact the „symhiotic''' relation of

112

sponge and greeri alga is, considered from the point of view of the
use to the sponge, we cannot verg well answer that qnestion, hefore
the prohlem, mentioned ahove, ahout the significmice for the sponge
of the O., secreted hg the green alga i?i the light, has come to
solutiofi :

a. If the significance of that O., is in f act so important, as tvas
fhought possihle above, we must conclude — notwithstanding the
fact, that the sponge continnallg destroys and digests numbers of
algae, and notwithstanding all otlier phenomena, tvhich do not seem
to go together with a sgmbiosis — that the reJdtion of sponge and
green alga, considered from the point of view of the use to the
sponge, is in fact a sgmbiosis, though this sgmbiosis is bg no
nieans so complete as that of the Lichens.

b. If, on the contrary, the significance of the 0.^ secreted bg the
alga is onlg of little importance, ive can conclude — whatever
mag be the real cause of the dying of the algae in the sponge
tissue, wether it be the want of food of the spo7ige or {and) the
„p)oisoning^' of the cdgae bg products of metabolism of the sponge —
we must conclude that, practically spoken, that so colled symbiotic
relation of spo?ige and alga is in fact nothing hut simply aprocess
of nutrition of the sponge, or, if gou like, a verg frst transition
of a process of nutrition into a symbiosis. At any rate this always
counts for a sponge in darhness.

For ive could state the folio witig :

The sponge continuallg imports green algae from. the surrounding
water into its amoebocytes {p. 50), where those algae then — it should
be explicitly mentioned — are killed and digested {p. 111) by the
sponge o?ily for a part, when circumstances are favourable;
tvhile the rest of the algae can live on, photosynthesise and mul-
tip)ly {and will give their f\, produced in light, to the sponge
tissues {p. 93) — the onlg argument one can mention iri favour
of the conception of symbiosis !). This favourable case is only realized
in spo7iges growing in light {p. 70^72) — for in light i y mo ') —

1) This foUows from p. 70 IV, p. 51, and p. 60 — 01, 59. In darkness i — mo; so in
light i > mo.

113

and f hen not even always (p. 41 ^ 75 — 7(i). If^ hoivever^ the circum-
stances are mmewhat less favourahle — as is the rule in sponcjes
in darkness {]>. (>■) — 70) and as sometimes happens also in those
in light {p. 41^ 70 — 76) — then all imported algae {and all that
mif/ht be present already) are continually and unavoidahly destroyed
and digested hy the sponge {p. 111).

What happens to the numher of green algae of a sponge under
certain circumstances^ entirely depends upon the value, which each
quanfity fakes under those circiimstances in this formula:

i -\- r + mu =.e -\- g -\- mo

the formula^ which we have got to know on p. GS — 75 as decisive
for the numher of green algae of a sponge.

For the „symbiosis" considered from the point uf view of the
use to the alga, I refer to p. 83 — 84.

In order to show even more clearly, how much the relation
of fresh-water sponge and green alga is still removed from a real
symbiosis (in the sense of mutualism), I want to mention what
we should require from a relation between two organisms, which
are closely connected, to be justified in calling this relation a
symbiosis (mutualism) : That relation should be one of mutual
use ; the symbiontes should be interested in each ethers
existence, so spare, if possible, even nourish each other. Both
the symbiontes should in fact behave as one, new individual —
in extreme cases, for instance, not be able to exist one without
the other and die together. The symbiosis should be kept up
simply by multiplication of both symbiontes ; but should not need
a continual supply from outside (import) of one of the symbion-
tes, to restitute the destroyed ones.

So ï^OLL (56) says about the Lichens: „Die Pilzhyphen umspin-
nen im Flechtenkörper die Algen, überlassen ihnen den zur As-
similation güastigen Platz . . . . , treten mit ihnen in innige Be-
rührung und entziehen ihnen einen Teil ihrer Assimilate. Dafür

114

liefert der Pilz nicht nur das, dvirch oft kraftige Saure-ausscheidung
gehaltreich gewordene Nahrwasser, sondern, wie es nach den
üntersuchungen Artaris walirscheinlich ist, auch Pepton, so dass
die Algen in dem Fleclitenkörper nicht nur nicht erschöpft werden,
sondern sogar sich kraftiger entwickeln als in freiem Zustande
und sich durch Teilung lebhaft vermehren." And Schenck (56) :
„Die Plechten besitzen untereinander so viel übereinstimmendes
in Bau und Lebensweise und haben sich als Konsortien" (of fun-
gus and alga) „phylogenetisch weiter entwickelt, so dass sie zweck-
masziger als besondere Klasse behandelt werden .... Die Symbiose
der flechtenbildenden Pilze mit Algen führt zur Bildung von
zusammengesetzten Organismen mit eigenartiger Form des ïhallus,
welcher entsprechend seiner durch die Algen bedingten selbstan-
digen Ernahrungsweise andere Gestalten als bei den nicht flech-
tenbildenden Fadenpilzen aufweist .... Nur für ganz wenige
Flechtengattungen ist festgestellt, dasz ihr Pilz auch ohne Algen
in der Natur existenzfahig ist".

I will not finish this chapter, before I have said somewhat
more about the often mentioned (p. 111, 103, 109, among others)
„poisonous" influence of the products of metabolism of the sponge,
which influence would be deadly to the algae. There was no
certain proof for its existence, but there were arguments for its
probability. For if it might prove that the want of food of the
sponge, mentioned on p. 111 and 109, cannot be accepted as a cause
of the dying of the algao in darkness, there remains as only
possible the one mentioned by the name of „poisoning by pro-
ducts of metabolism". The term is vague, but all the same gives
exactly what one would havo to understand by it.

Of course, I am not going to take the question once more in
consideration, which I said on p. 110 to leave till later on. But
I have made sonie interesting finds among my sponge cultures,
which certainly justify the question, if the sponge could exert
poisonous iufluences on other organisms (c. q. the algae), which
have come inside its body. In other words, if there would not

115

be some reason to accept, that here we should have to do with
a true reaction of defence of the sponge against tlie foreign in-
truder, in the way an unhealthy organism defends itsclf against
the infector.

I have foiind : 3 different types of algae (2 filamentous and 1
unicellular), which appeared to occiir in great number in the
tissues of several Ephydatiae (from the Brasemer lake near Leyden
and cultivated in my aquaria) (see chapter IX). Two of these,
the filamentous algae, proved to destroy entirely the sponge tissue
with their growth; the 3i"d, .the unicellular one, on the contrary,
after having penetrated the sponge tissue in the beginning — the
original colourless sponge had become light-green by it — was
finally conquered and destroyed by the sponge.

In the first place one could imagine this destroying as caused
by ferments of defence of the sponge, the above mentioned „poi-
sonous" influence of products of metabolism. But there is still
another possibility. It proved to me, that a sponge may eject
such unicellular „infecting" algae from its body together with
detritus (for instance captured carmine grains). (See lateron, in
the description of the defecation-process, chapt. E.)

8o here we have seen cases of positive infection of the sponge
by filamentous algae, by which the sponge was destroyed. But
we also saw a case, in which the sponge finally succeeded in
conquering and destroying the intruder — the unicellular alga —
which was spreading further and further.

That unicellular alga appeared to be probably a Pleurococcacea,
so closely related to the „symbiotic" alga of the Spongillidae
(p. 34). Is it not evident then, that one is inclined to see also
something in that „symbiosis", which is like an infection? An
infection, against which the sponge must also defend itself?

There is still another view in connection with the case of the
mentioned unicellular alga. If the „relation" between sponge and
„symbiotic" alga is no other than was mentioned (p. 111t-113),
it might be possible, that the sponge does not want one certain

116

alga for such a „relation", but that it would content itself with
all sorts of other unicellular algae, according to circumstances.
So for instance, in the case mentioned above, with a relative of
the normal „symbiotic" alga. In this way one might think possible,
in different countries, an association of our fresh-water sponge
with qnite different algae !

IX. SOME OTHER ALGAE OCCUKRINÖ IN THE TISSUES OF EPHYDATIA.

After the theoretical consideration to which these cases gave
reason I want to give now a short description with illustrations
of the 3 infecting filamentous and unicellular algae which I have
found. I must add that I have met with these algae not once,
but in several specimina of Ephydatia (never in Spongillae) ; but
only in one spring, and never in sponges immediately from nature,
but always in specimina which had been in my aquaria for some
time (2 — 3 months). Generally all 3 of them were to be found
together in one sponge, but the unicellular alga also very often alone.

The Ephydatiae infected by filamentous algae were to be re-
cognized at dark-green, almost emerald irregular spots here and
there in the colourless or light-green normal sponge tissue. The
sponges were also (partly) surrounded at the outside by those
algae, which freely spread in the water. Under binocular micros-
cope one could obserye very distinctly that those green spots
might be continued till within the sponge body, so under the
normal tissue; but generally they were to be found in tissue
layers more at the surface.

If one examined a picce of such a green tissue-spot under
oil-immersion, one found parts, where nothing but the skeleton
of the sponge tissue had remained, but the place of the cells was
entirely filled in by filamentous algae ; and next to that some
almost intact sponge tissue parts, in which however among the
normal sponge cells filamentous algae began to spread. One could
also see how such a growing algal filament quite makes an
exterior wall of the sponge protude (tent shaped), when trying
to pierce it from within.

117

On closer examination of the filamentous algae there proved
to be two different types present in the tissue at the same time
(Fig. 43 — 45, drawn after living material). The last one (Fig. 45)
consisting of long, 5 — 6 pi thick, unbranched filaments with girdle-
shapcd chloroplast appeared free in the aquarium as well as in the
sponge tissue. I think it to be Ulothrix subtilissima. The other
one (Fig. 43, 44), however, was never free in the aquarium but
only to be found in the sponge tissue. As one can see from the
illustrations (Fig. 43, 44), it consisted of often very irregularly
branched filaments, consisting of cells which could have all sorts
of shapes from cylinder- to almost ball-shape. The chlorophyll
was scattered all over the cell without any regularity — probably
in a great number of chromatophores, while very likely each cell
contained one nucleus. The filaments were about 8 — 9 (z thick.
As with a view to my other investigations I could not spend
much time on studying these infecting algae, I have not been
able to discover their mode of reproduction (nor of the other
filamentous alga). Nevertheless I want to draw attention to the
fact that this alga, given in Fig. 43 and 44, is much like the
Trentepohlia spongophila, which professor Weber and Mrs. Weber-
Van Bosse (64) found in 1890 also in the tissue of Ephydatia
fluviatilis, but of speciraina originating from a lake on Sumatra.

Finally I want to speak about the unicellular alga which, as
mentioned, appeared either alone or with the two filamentous
ones in the tissue of Ephydatiae. Where of course the latter were
situated between the amoebocytes, the unicellular one occurred
just within the amoebocytes, mostly free in the protoplasm, but
sometimes also in different stages of digestion within food-vacuoles.
The alga is shown in Fig. 46 — 52 (drawn after living material).
The shape was oval, the diameter 5,5 — 7^. The cell contained:
a chloroplast lining the wall, which let the centre of the cell free
and seemed to be one time single and another time composed of
several parts; next a rather big refractive globule and a number
of small refractive points, which, with different adjusting of the
microscope, were one time lilac-brown and another time blue-green.
The wall was rather thin. I have also found a stage of division

118

(Fig. 52); from whicli we see that „freie Zellbildung" does nut
take place, biit simple vegetative division of the whole cell.
Thougli I have not been able to give sufficiënt time to the
research into this alga either, I came to the conclusion that we
have probably to do with a Pleurococcacea, so with a relative
of the ordinary „symbiotic" alga of the fresh-water sponges.

Besides the 3 „infecting" algae mentioned here, there were
of course also the normal „symbiotic" algae in the tissue of the
„infected" sponges, hut their number was always relatively small.
It stands to reason, that there might be in general inside the
sponges — in the canal-system for instance — also quite otlier
kinds of algae as well as protozoa and also diatoms, whicli might
of course be captured at their turn by the sponge tissue to serve
as food, and so might get into the amoebocytes. But this cate-
gory does not come into consideration here at all. Ilere we have
only to do with the algae, whicli appear aud keep up either
regularly (the symbiotic alga) or accidentally (the 3 infecting
algae) in a great number within the sponge tissue.

B. THE CURRENÏ OF WATER IN THE CANAL-SYSTEM.
OF THE FRESH-WATER SPONGES.

As mentioned in the Introduction, I have found out a method,
which enables us to observe wholly intact, normally living tissue
of sponges with an oil-immersion for many hours, on several
consecutive days. The way in whicli the necessary microscopic
preparations were obtained is indicated above on pag. 12 — 13.
It was by means of these living preparations that I have been
able to state, that the generally acknowledged theory concerning
the cause of the current of water through the sponge body is
not right, as it is based on a mode of movement of the flagella
of the choanocytes, which proved to me abnormal and caused by
exhaustion.

Anatomy. — Before proceeding to the examination of the

119

watercurrent, 1 want to givc a description and a diagraniniatic
illustration (Fig. 53) of the canal-systein in frosli-water sponges.

They are taken from Delage and Hérouard (1G) 1S99: „

La surface (de la Spongille) est soulevée par les extréniités sail-
lantes des spicules (Fig. 53 cnli.), qui lui donnent un aspect
hérissé; §a et la se voient quelques oscules (os.), assez larges,
irrcgulièrement distribués. L'Eponge est partout, sauf naturelle-
ment au niveau des oscules, revêtue d'une mince membrane der-
miquc (ecfs.) dans laquelle sont percés les pores (p.)" (better:
ostia) „et qui formc la voute d'une vaste cavité hypodermique.
Cette voute, malgré sa minccur, contient des éléments mésoder-
niiques, parmi lesquels des cellules contractiles, et est tapissée
sur ses deux faces d'un mince épithélium de pinacocytes. La
cavité hypodermique {cv. hy.) est continue mais traversée ga et
la par des spicules ou des faisceaux de spicules, qui se drossant
des parties profondes, soulovent sans la percer la membrane der-
mique. Le plancher de la cavité hypodermique formé par la sur-
face du choanosome est criblé de trous, de taille tres inégale,
qui sont les orifices d'entrée du système inhalant. Les canaux
inhalants {en. inh.) piongent dans le choanosome et s'y ramifient
largement, mais sans aucune régularité ni dans la forme, ni dans
la distribution de leurs branches. — De chaque oscule part un
large canal qui plonge directement dans la profondeur, formant
une cavité atriale irreguliere {cv. air.) d'oü partent en tous sens
des canaux exhalants {en. exh.) d'abord a direction taugentielle,
puis ramifiés "dans toute l'épaisseur du choanosome sans plus de
régularité que les canaux inhalants, ni sous le rapport de la
forme, ni sous celui de la distribution. — De la sorte, l'Eponge
tout enticre est réduite a un système caverneux de cavités ex-
trèmement irrégulières, les unes inhalantes plus étroites, plus
canaliformes, les autres exhalantes plus spacieuses, plus caméri-
formes, intriquées en tous sens, réduisant la parenchyme {chs.) a
des cloisons peu épaisses. — Mais, au milieu de cette irrégularité,
une règle persiste, absolue : c'est la non-communication directe
des systèmes inhalant et exhalant, qui restent séparés. Toutes les
lacunes inhalantes communiquent entre elles, toutes les exhalantes

120

de même ; mais pour aller des premières aux secondes, on se
lieurterait partout a une cloison de choanosome. Dans ces cloisons
sont les corbeilles, petites, arrondies, dépourvues de prosodus et
d'apliodus, s'ouvrant d'une part dans les lacunes inhalantes par
deux a cinq petits orifices prosopylaires et d'autre part dans les
lacunes exhalantes par un large orifice apopylaire, ce qui permet
de distinguer sur les coupes les deux sortes de lacunes. Dans ces
cloisons sont aussi, entre les autres éléments mésodermiques ....

les spicules formant dans Ie réseau du choanosome un

réseau squelettique Ces spicules sont soudés entre eux, soit

dans toute leur longeur, soit par leurs extrémités seulement, par
la spongine".

Delage and Hérouabd's illustration with few alterations
(Fig. 53) gives rather a good idea of the canal-system ; it is, how-
ever, but a diagram. A better illustration of the surroundings of
the flagellated chambers in Spongillidae is given by Fig. 54.

Finally a beautiful illustration of a flagellated chamber of Spon-
gilla lacustris (Fig. 55) is taken from Vosmaer and Pekelharing
(61). The authors mention that this figure was drawn with great
care from a very carefully preserved preparation. The apopyle
(rt^?.) and the excurrent canal is shown. The figure represents a
s e c t i o n of a chamber ; therefore we see but one flagellum at
its real length. The thin line uniting the bases of the choano-
cytes represents the outline of the chamber. So we see that the
chamber is lined by the well known choanocytes, whose collar
and flagellum can be easily distinguished in the figure as well
as their nucleus, a vacuole (at the base of the flagellum) and a
certain number of black spots, which are doubtless the above men-
tioned (p. 90, 9) oildrops. Finally I want to mention that the
choanocytes are able to entirely retract their collar and perhaps
also their flagellum.

Fuiiction. — Proceeding to the description of the water-cur-
rent in the canal-system, I want to remind in the first place
that the water enters the inhalant (incurrent) system through the
ostia, it then passes from the incurrent canals trough the proso-

121

pyles iutü the flagellatod eliambers and from there through the
apopylcs into the exhalant (cxcurrent) system, in order to finally
leave the sponge body by a large osculum (Fig. 53, 54).

This c^irrent of water is caused by the movements of the
flagella of the choanocytes in the flagellated ehambers, as is
generally acknowledged. The great question which had been dis-
cussed for ever such a long time, and which seemed decided in
1898 by the research .of Vosmaer and Pekelharing (62) — as
mentioned in the Introduction — was: what is the exact way in
which the flagella move; how is the movement of the water
within the flagellated ehambers ; how is the whole water-current
explained ?

It is a matter of course that, on account of the difficulty of
the research, one has not been able to make many direct obser-
vations concerning this question. So Lieberkühn (38) says to
have seen the movement of the flagella in Grantia botryoides
(a calcareous sponge), viz. „Wimpern" which „ausserst lebhaft
schwingen"; he does not give more details. Bowerbank (7),
however, says about the flagella of Grantia compressa: „When
in vigorous condition their motions are rapid and cannot readily
be foliowed, but in some in which the action was languid, the
upper portion of the cilium was thrown gently backward towards
the surface of the sponge, and then lashed briskly forward towards
the osculum, and this action was steadily and regularly repeated.
Their motions are not synchronous, each evidently acts indepen-
dently of the ethers", v. Lendenfeld (37) says — I quote from
Vosmaer and Pekelharing — : „it appears that the cilia in the
entodermal collar-cells move, pendulum-like, backward and for-
ward, similarly to the cilia of the polyciliar epithelium-cells in
the respiratory-tracts and other parts of vertebrates" — a remark,
however, apparently not based on observations. Finally Cotte
(13): „on peut voir Ie mouvement des flagella se produire sous
forme d'ondes, avec un rythme particulier au moment ou se fait
l'observation, inais qui a ce moment est Ie même pour tous les
flagella d'un même territoire" (so in the way of polyciliar epithe-
lium). „Par centre, a cóté des cellules a mouvement regulier, on

122

en trouve d'autres qui ont une allure absolument désordonnée".

And: „ Ie mouvement des flagella est comparable a celui

d'un fouet Ie mouvement de l'eau resultant de l'action des

flagella doit etre, dans l'ensemble, perpendiculaire a Taxe des
choanocytes".

In close relation to these interpretations of the motion of the
flagella (as Fig. 56 r/, bid) is the way in which the movement of
the water within the flagellated- chambers was supposed to be.
In the theory of Bowerbank, Lendenfeld (and of Cotte) one
should imagine this movement to be regular and rapid, passing
from the prosopyles through the chamber to the apopyle. In
this way, ho wever, it would not be clear how the sponge is
able to capture the food particles from the circulating water;
for the greatest deal of it would flow rapidly through the canal-
system without ever having been in contact with the cells
liniiig the canals! Cotte resolves this difficulty in the following
way: „Il est certain que cette disposition morphologique" (of the
prosopyles) „a pour résultat la formation d'un remous ou d'un
tourbillon au point oü l'eau pénètre dans la corbeille vibratile.
Dans cette dernière les flagella, par leurs battements actifs, pro-
duisent un brassage énergique de l'eau et par conséquent des
particules en suspension dans celui-ci". And: „Il y a en ce point
contact plus iniime de l'eau et des aliments qu'elle ren-
ferme avec les choanocytes qui sont les organes de l'absorption".
But this seems to be based on reasoning, not on personal observation.

Therefore it has been the great importance of the theory of
VosMAER and Pekelharing (62), that, based on experiments and
observations of the motion of flagella and the vrater-current itself,
it explained these phenomena in such a way, that it was evident
at once that such a movement of the water in the flagellated
chambers, as was stated by the investigators, was exceedingly
fit for bringing food particles within reach of the sponge-cells.

I am now going to treat Vosmaer and Pekelharing's theory
more at large, as it has also been the starting-point of my own
research. Their principal experiment, giving most important obser-
vations, was made directly in the neighbourhood of the habitat

123

of the sponge on a thin-walled Leucosolenia, a tube-like calca-
reous sponge, the inside of which is entirely covered with choa-
nocytes. I will quote now: „A piece of about 1 cm. was out from
a tube and then split open and immediately observed. The piece
was covered with a cover-glass ; but this could hardly harm the
choanocytes, as it was carried by the apical rays of the tetra-
sclercs. The preparations were observed with Zeiss's homog. imm.
1.40, 3; Oc. 12. It was evident then that the flagella were beating
quite independently from each other, all in different directions"
(as Fig. 56 f/, 57 rf, 58 i). „The movement of each flagellum was
not always in the same plane, and one moment it was stronger
in one direction, another moment stronger in another. Sometimes
a flagellum was stretched for a while almost horizontally. It
happened also that one or more flagella were motionless, in order
to beat again vividly a few moments afterwards. Every now and
then flagella crossed, without ever becoming entangled. Particlcs
suspended in the water were whirling about, never carried for-
ward. In short, the aspect of the motion was absolutely different
from what is observed in ciliated membranes of higher animals.
There was no tracé of a coordination of neighbouring cells".

The authors continue :

„. . . . this mode of motion cannot be but advantageous for
capturing particles by the choanocytes. This is not only the case
for choanocytes forming flagellated chambers, but eminently so
for those lining the cloacae of Leucosolenia. If all the flagella
lashed briskly towards the osculum, the particles, entered through
the pores, would be directcd chiefly towards the axis of the tube
and rapidly removed through the osculum. On the contrary the
movement of tlie flagella has the effect that particles can easily
reach the collars and thus come into contact with the protoplasma
of the choanocytes".

„Moreover it seems possiblu to us, to explain by the irregular
motion of the flagella, the regular current through the canals of
the sponge, as this is so often observed, and so carefully studied

by Gkant it seems to us that in the living sponge the

water w^ould find more resistance in flowing out from the chamber

124

through a pore than it finds in streaming in. For we found that
in carefully mounted preparations where all the choanoeytes re-
mained fixed in their place, these cells surround the pores closely
and are placed, not exactly perpendicular on the wall, but some-
what oblique, so as to narrow the cloacal opening of the pore.
We found this to be the case in a flat, stretched piece of Leu-
cosolenia. Their position raust be all the more oblique in the
living state if the wall is of course not flat but concave. If
therefore in the cloaca the pressure of the water becomes higher,
the collars of the choanoeytes will become somewhat inflated and
the pore will be narrowed. If, on the contrary in the cloaca the
pression of the water in the neighbourhood of a pore is lessened,
water can easily flow in through the pores ; the choanoeytes with
their collars thus act as valves. Now by the irregular motion of
the flagella the pressure on the wall of the tube, which by the
spicules is kept rigid, is continually changing. If the pressure
becomes higher, this is of little eff'ect, but if the pressure becomes
less, water will flow in through the pores, as long as they are open.
The sponge will thus suck iu water, which will leave the body
again through the osculum".

Thus Vosmaer's and Pekelharing's theory. Then the investi-
gators call attention to the fact that the arrangement of the canal
system of the sponges becomes more and more appropriate accord-
ing as one examines higher developed forms.

Personal Research. — Hoiv much this tJieorij of Vosmaer and
Pekelharing's may correspond with their observations and hoiv well
it may make us miderstand that ivith such a movement of the tvater
a (jreat number of foodpartides are brought uithin the reach of
the choanoeytes^ it could not quite satisfy me froni the beginning.
It appeared very unlikely to me that the flagellar motion of
the choanoeytes should principally be quite different from that of
the unicellular Flagellaia eg. the Choanofagellata^ which for the
rest remind ns so much of the choanoeytes. This supposition was
the more tompting, because it would make us quite independent
of the synchronism (whether existing or not) and of the direction

125

(whether mutually deviating- or not) of the separate flagellar beatings.

The movement of the flagella, which had hitherto been established
in the choanocytes, was a rowing-movement (as Fig. 56 f/, 57 rf,
58 6) ; so a motion which is not peculiar to the long flagella but
to the short cilia of the protozoa; while, on the contrary, the
flagella of the imicellulars are moving in spiral-lines (compare
DoFLEiN 17). If the latter, now, could be proved to be also the
case with the choanocytes, than the solution would be quito easy.
For the spiral- or screw-motion of the flagelUim of the unicellu-
lars pushes the water on, just as the screw of a steamer, in the
direction of and turning round the axis of the flagellar spiral,
either towards the cell (Flagellata) or in the opposite way
(spermatozoa). — This is simply determined by the fact, whether a
spiral wave (optically) moves on from the top to the base of the
flagellum or in the opposite way; but I will not enter further
into this question here. — If in the choanocytes the motion of
the flagella took also place in this manner (as a spiral), it is a
matter of fact, that by the action of all choanocytes of a flagel-
lated chamber together there should be a constant flow of water
either from the centre of the chamber towards the wall or from
the wall towards the centre, provided that the spiral-motions of
all choanocytes moved on in the same way. We would how-
ever not have anything to do with their synchronism or their
direction. Now, according to Doplein (17) the Choanoflagellata
push the water off along the axis of the flagellar spiral. Might
it not be possible then that the same should count for the cho-
anocytes too?

The question was therefore to observe the movement of their
flagella under circumstances that were as normal as possible. On
the other hand one had to claim, that the study of the flagellar
motions and of the water-current, produced by as niany choano-
cytes together as there are within a flagellated chamber, had to
be preceded by an accurate research into the motion of the fla-
gellum of one, isolated, choanocyte and into the water-current it
caused in a free and open space.

Now, I can state that I have succeeded in both ways. The study

126

of the movement of the isolated choanocytes^ as well as of that in
the intact flagellated chambers^ has shoimi me that the flagellar
motton, under normal circumstances, is in fact the same as that of
the Flagellata, viz. the Choanoflagellala : a spiral- or undulating-
motion; but that this movement, after exhaustion, very soon
changes into quite a different one, viz. the rowing'-motion.

The research into the motion of the fiagella of isolated choano-
cytes was made by me in February 1915. In fact it is best to
be done in winter, at a low temperature. For one has to make
use of ravel-preparations (p. 12) of living sponge tissue, which
one watches as soon as possible with oil immersion in an Engel-
MANN case. As in winter Spongilla dies, only Ephydatia was to
be used for this research.

I shall now give a description and some illustrations of the

flagellar motion, which could be beautifuUy observed owing to

the isolated situation of the choanocyte at the top of a number

of other cells. For the observation, namely, one must have the

flagellum isolated, but on the other hand the choanocyte itself

may not be separated from the others, but it must, just as in

the flagellated chamber, be fixed quite fast with its base to have

a support against the heavy vibrations of its flagellum. I have

noted the description literally during the observations and the

figures were drawn immediately from the living material :

5.55 p. m. Flagellum shows very 7-apid nndidating-motions

(immediately [prohahly in spiral-Une) of small amplitude. The

^ ^^ water with the particles is pushed away stronqly,

isolation) . ^ ^ i^ j v'

straight through the axis of the flagellar spiral, while
at the side it flous on to the base (Fig. 56 a).

5.57 p. m. The amplitude of the flagellar motion becomes
much greater, the movement less quick. The water
with the particles is still pushed on through the
axis. of the spiral, while at the side it flows towards
the base (Fig. 56 è).

G.00 p. m. Just a slight undulating-motion to be seen, very
large amplitude, even less rapidity. ïhe water with

127

the particles is at first stirred to and fro, but finally

pushed away in upward slanting direction (Fig. 56 c).

6.10 p. m. The last movement (Fig. 56 c) was evidently a

transition from the spiral- or undulating-motion to

this new one: A slow ') heating to and fro of the

fiayelluni, unthout waves. The water with the particles

is moved to and fro^ but it is not2Mshed aivay (Fig. 56f/).

6.15 p. m. The ftagelluni stops in a more or less straightened

condition (Fig. 56c).

To this I must add that after the phase, given in Fig. 56 «, the

motion of the flagellum became less rogular; it was intcrrupted

by resting-periods of unequal, but ever increasing length till 6.15

p. m., when it stopped finally. There was no collar to be seen in

this choanocyte, evidently it had been retracted.

One will acknowledge, now, that the first phase (Fig. 56 a) of
the flagellar motion is in fact quite different from that which
the investigators have hitherto observed. It goes without saying
that the water current caused should prove quite a different one
also. But there is still more to be seen in the figures: the mode
of motion of the flagellum, hitherto described (by Bowerbank,
Lendenfeld, Cotte, Vosmaer and Pekelharing), fully agrees
with our phase given in Fig. 56 fZ — even the current of water!
Now, the phase of Fig. 56 d however is quite abnormal, and caused
by exhaustion, as after 5 mnts. it is already foliowed by final
stagnation of the flagellar movements. The explanation, why these
last phases (Fig. 56 c, c?), the rowing-movement, have always been
found by the investigators and never the first one (Fig. 56 «), the
serew- or undulating-motion, is quite clear now. Moreover, I will
just call attention to what Bowerbank said, as I quoted already
on p. 121 : „When in vigorous condition their motious" (of the
flagella) „are rapid and cannot readily be foliowed, but in
some in which the action was languid" etc! Prohahly one
has alivays observed the movements of more or less exhausted flagella.

1) Thnt is to say, comparod with Ihe former intense motion; it still goes rather
quickly.

128

I say „probably"; for I can only speak of the motion of the
flagella of the Spongillidae ; it might be possible, though to me
it does not seem very likely, that in other sponges the movement
is quite a different one.

It stands to reason that my observations are not confined to
the one given hero. I have made many, and all of them with
the same result. I shall not describe them again, but I will only
give a few illustrations ; they speak for themselves (Fig. 57 a — f).
The same for a number of choanocytes still joined within a part
of a flagqllated chamber (Fig. 58 a — c).

Alivays — in favourahle conditions of course: the choanocytes
are often immediately damaged — the motion of the flagelhim
was at first a rapid succession of (spiral-) waves of small ampli-
tude. The waves ivere moving — without any exception — from
the base to the top of the flagellum; and consequenthj the water
with the particles was pushed on from the cell quickhj and in a
straight line through the axis of the flagellar spiral^ ivhile it flowed
toiinrds the base laterally. One can understand that with such a
rapid succession of actions it was not easy to make out, whether
the flagellum moved exclusively in one plane, as a flat motion,
or as a spiral one; one time it showed a flat wave, next deci-
dedly a spiral ; however, it does not matter very much. (I will
revert to this subject later on.)

After a short time this regular, rapid motion passed always
into a slower, less regular one, during which at first the un-
dulating-motion (and the water current) persisted, but this soon
ceased, to pass into the still slower and more irregular rowing-
motion, by which the water was only stirred a little, and no
more pushed away. The end was absolute stopping of the stretched
flagellum ; but not always for long. Sometimes (Fig. 57) the mo-
vement began again after a quarter of an hour's rest, but very
seldom the original rapid undulating-motion (and then only for
a few moments), but more the later phases, alternatively, now
the rowing-motion (Fig. 57 d)^ then the „lash" (Fig. 57 e)] and not
fluent but jerking, interrupted by periods of rest, and very soon
foliowed by entire stagnation, the flagellum (Fig. 57 /') stretched

129

out. Such a period of weak motion may be repeated scvcral times.
As is shown in the figuros, the collars were sometim es visible
for a small part; generally they appeared more clcarly when the
motion had almost ceased (sign of relaxation of the protoplasm-
contractility when death is approachiiig?).

We might now go into a theory about the contractions of the
protoplasm, which must take place in a flagellum in order to
bring about these (spiral-)waves. And we should be the more
justified in doing so, Ist because the spiral- or undulating-motion,
as we shall see presently, is in fact the normal way of flagellar
movement of the choanocytes, and 2nd because in my opinion it
is very likely that in the changing of this movement by exhaustion
we could find a good starting-point for such a theory about its
mechanism.

As all this, however, would only be more distantly connected
with the subject we are treating at present, I prefer to leave it
till lateron.

Though we may have shown now, that the normal motion
of the flagellum is more likely a spiral- or waving- than a
rowing-motion, as the former investigators had found, we have
not yet proved, however, that the normal motion of the ftcu/ella
within the intact flagellated chamhers is really also a spiral- or
undulating one. For up to now I described observations of ravelled
sponge tissue.

. Herh my method^ which makes it possible to observe wholly intact
normally living sponge tissue with oil-immersion for a long tinie^
has rendered me good service. This method has been described on
p. 12 — 13. Only Spongilla is fit for it (as Ephydatia grows too
slowly) and exclusively in summer. If the microscopic preparations
have been made with care and if the ontward circumstances have
been favourable (sufficiënt warmth !), then we find, within a week's
time, the vigorously acting flagellated chambers with in- and ex-
current canals everywhere in the sponge-rim — so in the newly
formed tissue.

130

A remarkable sight to watch siich a flagellated chamber! At
first one sees only a round hole into which, so to say, the water
runs in from all sides in incessant current, like a round cas-
cade (the water disappearing in the middle).

Of course, this is only optical delusion. The current of water
itself cannot be observed, and what one took for the undulating
streamlets are simply the (spiral-)waves of the flagella, that run
on from all sides of the chamber to the centre. For the choano-
cytes are, with their base, attached to the inside of the wall of
a globular space (the chamber), so the flagella are all directed
towards the centre (Fig. 55). The collars will be treated lateron.
Examining now the flagella very accuratelg, one immediately
recognizes the fagellar tnotion^ that we have got to knoiv above as
normal in the isolated choanocytes {eg. Fig. 56a)] hut this one here
is much stronger! The (spiral-jiraves are running on very clearly
in rapid succession from the base towards the top of the flagellum ;
their amplitude is very small, still smaller than Fig. 56« shows;
sometimes the flagellum is almost stretched ; another time it seems
as if there are some smaller waves superposed on the larger ones,
which is certainly possible.

An accurate illustration of such a strongly acting flagellated
chamber is given in Fig. 59, drawn from nature. Beside the (ge-
nerally occurring) very rapid spiral- or undulating-motion some
flagella of a chamber may show a somewhat slower one with a
larger amplitude, in the way as shown in Fig. 56 b. Probably,
this last phase is inserted now and then, as a rest-period, be-
tween the normal, quick undulatings ; I at least saw it sometimes
pass into the rapid one.

For hours one may observe the movements ; one n e v e r sees
any other than those, mentioned here : the quick (spiral-)waves
with now and then a slow one between. I have observed them
ropeatodly in numerous diiferent preparations, in the course of
scveral years (1915 — '16 — '17); always with the same result.
Also, Professor Yosmaer and Professor Pekelharing — I am
very glad to mention — have enabled me to demonstrate to
them, in my living preparations, the flagellar motion of the in-

131

tact chambers, described hcre. Both considered my conception as
convincingly proved by the preparations.

As an exception, however, the chambers did not show these forms
of the flagellar motion. It occasionally happen«d, that af ter liours
of observation and experiment (with carmine) the movement became
different: a relatively very slow one, and no more the normal
but the same abnormal ones, which I have described in Fig. 56 ft-o?,
as being caused by fatigue and exhaustion. Accordingly, they
were always soon foliowed by entire stopping.

Now the collars and cell-bodies of the choanocytes need treating.
The cell-bodies, in my living tissue preparations, were in general
not to be distinguished separately, as one easily understands; one
only sees their joined layer as a whole, round the chamber ; just
as is given in Fig. 59.

The collars are to be seen in great number in the chambers;
they are very long and leave their flagellum uncovered only for
rather a short part at the top (Fig. 59). (I will return to this
subject.) Watching a collar vertically on its longitudinal axis, one
never sees its apical edge ; evidently, this is so thin that it es-
capes to the eye. In this way of a collar one only observes two
straight lines (the extending wall) at the side of the flagellum.
As there are such a great number of cells in a chamber, it is not
astonishing that one often has great difficulty in finding oiit the
flagellum with its own two coUar-lines (of course, one immediately
distinguishes the former from the straight collar-lines by its
motion). It is quite an other case with the collars on the top
of which one can look; so when our eye is in their longitudinal
axis. Then one sees the edge of the collar very distinctly (as a
little circle), in which the flagellum (as a tiny spot) (Fig. 60). Of
course, I could not give all this in Fig. 59 ; I, therefore, only for
clearness' sake have drawn the apical edge of some of the collars,
though in fact they can not be distinguished in this position.

Finally I should mention that I have never observed anything
of the so called Sollas' membrane ; this quite agrees with the
results obtained by Vosmaer and Pekelharing (61).
- I now still have to speak of the shape of the flagellar move-

132

ments. Is this in fact a spiral, or is the whole wave in one flat
plane? It could not be made out very well in the isolated choa-
nocytes ; but all the better in the intact flagellated chamber. For
there we see, as I said before, a number of collars from above on
the top (as a circle), the flagellum within (as a spot) (Fig. 60). It
then proves that that spot — the section of the flagellum —
usually describes a flat ellipse or an almost straight line (Fig. 61, 62);
consequently, that the flagellum itself performs its undulating-
motion either as a flat spiral or in one flat plane. (As above
mentioned, this makes but little diff'erence to the eff'ect on the
water).

So ive have shoini definitively that the normal flagellar mofion
of the choanocytes is : a very rapid succession of (spiral- jwaves of
small ampUtNde, yoing on from the base to the top of the fla-
gellum {Fig. 56 a^ 59) and causing a current of water straight
through the axis of the flagellar spiral also in the direction from
base to top^ while the water floivs laterally towards the base. Ex-
haustion causes wholly differe^it flagellar motions with abnormal
current of water.

The water-current caused by all the flagella together in a fla-
gellated chamber must of course be the resultant of all the little
currents, caused by each of the flagella separately. We have got
to know the current of water during the normal motion of the
flagellum of the isolated choanocytes (p. 126 — 128). Within a
flagellated chamber the current of water, caused by each flagellum,
must, as the mode of moving of each flagellum is the same,
necessarily be equal to that which the flagellum would show in
isolated condition of the choanocyte; so here there must be again
for each flagellum a current of water through the axis of the
flagellar spiral away from the cell, so now directed towards the
centre of the chamber, while the water flows on towards the
base of the flagellum laterally (Fig. 58a). The irhole trater-current
within the fagcllated chamber^ as the resultant of all little currents
(■(iHscd 1)1/ ('dcli flagellum sc/xn-tdcli/j ra)i br ukkIc rlcar i)i the best

138

ivaif hij a diagrammatic figure {Fi(j. 63). This figure does not
nood special explanation ; it is planned after Fig. 55, inentioned
above (p. 120). It sJwivs hoir the water must flow rcq)ldly and
rcrjuhtrly from the prosopyles (there is onhj one indicated here,
hut there are 2 — 5 in a chamber) between the cell-bodies and the
collars of the choanocytes to the base of the flagella {here really
the opening of the collars), to be pushed from, there by the fta-
gellar motions to the centre of the chamber, thence to floir airay
through the apopyle. It is impossible to prove here (eg. by adding
carmine) that the current of water has indeed entirely this
course, because — the next chapter will show this — the carmine
grains, carried along by the water between the choanocytes, are
kept there. This penomenon, however, proves already quite
siifficiently that the Avater-current within a chamber has in fact
the course given here (Cnf. Fig. 65, 66).

If one asks about the differences of the water-pressure within
the canal-system of the sjwngCj it is quite clear that, with tlio
diagram given here (Fig. 63), this pressure must bc highest in
the centre o£ the flagellated chamber (higher than in the sur-
rounding water) and lowest (lower than in the surrounding water)
at the flagellar bases, while it is increased exactly in and by the
zone of the flagella. In order that a powerful, steady current
may be maintained by the chamber and that, therefore, the water
may enter rapidly and exclusively at the prosopyles and flow
out by the apopyle, the structure of the flagellated chamber must
comply with definite requirements. And these requirements do
not only count for the sponges of the type of Spongilla but mu-
tatis mutandis for sponges of any canal-system, either Calcaria or
Incalcaria (provided of course that there exists the same flagellar
motion). These requirements are: that the incurrent openings
(prosopyles, pori) of the chambers (mastichore) are relatively
narrow, the excurrent openings (apopyles, osculum) relatively
wide and that the former are placed among the choanocytes (all
this is generally realized). For the high pressure in the centre
of the chamber naturally makes the water flow out through the
largest opening, while over and above the flagellar motion in

134

connectioii with the placing of the prosopyles among the choano-
cytes prevents any ovitflow by this last way. On the other hand
the low negative pressure, that rnles at the base of the flagella
and consequently in the whole zone of the cell-bodies of the
choanocytes, must suck iip the water from as near as possible,
so here through the prosopyles 5 while moreover all water dis-
placement from the centre of the chamber, therefore also from
the apopyle, to the base of the flagella is excluded by the action
of the latter (perhaps except on the apopylar edge of a choano-
cytic" layer, so there, where this one passes into the pinacocytic
covering; but this water displacement is either of little impor-
tance (Homocoela) or measures must have been taken against it
— • more about this later on).

So in fact we must be able to distinguish always three sharply
separated pavts in each acting flagellated chamber with regard
to its contents of water: Ist the zone of the negative pressure,
that is the zone of the cell-bodies of the choanocytes with the
prosopyles; 2n'l the zone of the flagellar fuuction, so the zone in
which the water-pressure is increased from negative to positive;
3''d the zone of the positive pressure, that is — let me say so
for the present — ■ the centre of the chamber with the apopyle.
All passing of water from the S'"! into the l^t zone must be ab-
solutely excluded ; of course also immediate passing from the
l^t into the 3'''i; but passing from the l^t into the 2°^ and from
the 2'"^ into the 3''<i zone must certainly take place, and that as
quickly as possible.

Besides the above mentioned relative width of the in- and
excurrent openings and the situation of the former among the
collar-cells, also the situation of the choanocytes with respect to
the excurrent opening must be considered as an important factor
for a good regulation of the water-current within a flagellated
chamber. The movements of the flagella together give a certain
direction to this current, so if there is an opening in the wall
of a chamber exactly in the direction of that current, it is in-
evitable that the water will flow out by it. The importance of
this factor appcars very clearly from both these cases: the first.

135

taken frum Schulze (52) and alroady nientionod l)y VosMAKit
and Pekelharing (62), reg-ards sponges which show tlH3 diplodal
type of canal-system, wliere in general there does not seem to
be such a great difference in widtli of the prosodi and aphodi,
as both are narrow. It now appears that here (in Chondrosia eg.)
the fiagellated chambers are pear-shaped and that they only carry
choanocytes at the side, opposite to the „stem", while the „stem"-
side is covered by pinacocytes. Now the „stem" is formed by the
excurrent canal, while the incurrent canal ends among the choano-
cytes. It is a matter of fact that, with such a structure, the sepa-
ration of the fiagellated chamber into the three pressure-zones
wanted is guaranteed.

The importance (to the water-current within a sponge) of well
placed choanocytes, with respect to the apopyle of a cliamber,
appears, however, even more clearly from what I have been able to
state on my living microscopic preparations of Spongilla. It proved
several times, when I had the chance to observe a fiagellated
chamber with its excurrent canal exactly from the side, that here
too the choanocytes are almost exclusively attached to the wall
opposite to the apopyle (see also Fig, 55, after Vosmaer and
Pekelharing) and that, when moviiig, all flagella are directed
towards that opening, that even, sometimes, they are beating
with the tops outside the apopyle, so in the excur-
rent canal (Fig. 64, 73). The latter is of much importance, as
will soon appear.

First something else. On p. 131 I mentioned that the collars
only left their flagellum uncovered for rather a small part at the
top (Fig. 59). The consequence will be, that the flagella only in-
fluencc the water with a small part (the top outside the collar) ;
for it goes without saying that the water-circulation within the
narrow collar can not be important and, besides, will be closed
for the greater part in itself. Consequently, the chocanocyte pos-
sesses in the length of the collar a very good means of regulating
the effect of its flagellar motion: the shorter the collar, the strenger
the effect. One might make the objection that energy would then
be wasted by the flagellar motion within the collars. But con-

136

sider that the onergy which is lost there for the sponge cannot
possibly be of much importance, as hardly any water is moved
and, besides, the water that is moved circulates for the greater
part closed in itself, as I mentioned.

Let us return to our question. What does it mean when on
the one side we see in a Spongilla that only the tops of the
flagella protrude outside the collars, and on the other side that
sometimes these tops are beating outside the apopyle (Fig. 64)?
That means that in such a case Ist the centre of the flagellated
chaniber with the apopyle has become zone 2, the zone of the
flagellar function, so of increasing pressure, and 2iid that zone 3,
that of positivo pressure, is removed from the chamber into the
excurrent canal. Consequently, it is absolutely excluded that any
water might flow from zone 3 into zone 1; and the more so, as
we know that the apopyle is always much narrower than the
chamber itself (I even think to be justified in supposing that it
may be able to change its lumen as a sphincter ; which Weltner
too mentions (65) ). One can also understand, however, what a
powerful effect the motion of so many flagella crowded together
in an apopyle, and all of them acting in one direction, must
have; what a very strong current of water it must cause!

In the same way as I have described here for the flagellated
chambers of the Spongillidae, there will also be accessory arran-
gements to be discovered in the chambers of the other sponges,
helping to perfect the circulation of the water; of course always
by improving the system of the 3 zones of pressure, mentioned
on p. 134, and the rapidity of the removal of the water from
the Ist into the 2nd and into the 3i'd zone.

Of course there occur also a number of accessory arrangements
outside the flagellated chambers — in other parts of the canal
system — for the same purpose. For shortness' sake I will not
enter into this question here ; and the more so, because it has
been treated in extenso by Vosmaer and Pekelharing (62) and
my results do not give anything new.

So we have seen in tJiis cJiapter that the current of water throagh

137

the canal-aijstem of the fresh-water sj^omjes is caused hy the //a(/c/lar
motion of the choanorytes in the fiagelltited chambers. This motton
(in normal condition) takes lüace in a sinral- or an undulating-
line, naincly in a very rapid succession of waves of small ampli-
tude^ passing along the fiagellum from, the base to the top) (Fig. ■~)(Ja,
59) ; by which a current of water arises straight through the axis
of the flagellar spiral^ and similarly in the direction from base to
top, ivhile the ivater flous on at the side of the base {Fig. öGa).
Exhaustion causes quite different motions of the fiagellum, uith
almormal current of icater {Fig. 50 b-d). The ivhole water-current
ivithin a fagellated chamber is of course the resultant of the little
currents caused by each flageUum separateUj ; it is rapid and re-
gular {Fig. 63). In order that a poiverful and steady current inay
be maintained by the chamber, and that, therefore, the water will
■fioiv in quicMy and exclusively at the prosopyles and flow out by
the apopyle, the structure of the fiagellated chamber must comply
with definite requirements. This structure must be siich that:

a. the 3 zones, ivhich can be distinguished in a fimctionating
chamber, 2«' the zone of negative, 2>td that of iticreasing,
3^'d that of positive water-pressure, remain absolutely separated,
so that no water can pass from one zone into the other in
any other way than from the 1^^ into the 2"^^ and from the
2>"i into the 3<-^ zone (Fig. 63).

and that:

b. this u-ay of passiyig of the water goes as quicJdy as possible
(Fig. 64).

Finally some separate poiiits:

The motion of the flagella in the chambers does not change
when the ostia close, as I repeatedly statod.

Besides the above (p. 135) mentioned function of rcgulation
of the current, we can probably ascribe to the coUars that of
protcction of the flagella against injiiry and mutiial entanglement.
A third and much more important function will be treated in
the next chapter.

Finally I should mention that Delage and Héroüard (1G)

138

1899 aud Sollas (53) 190G, either of thom in thoir own way,
must have feit something of the theory, described and proved
hcre, of the movement of water in sponges. Sollas is nearer the
truth than both the other invcstigators ; none of them, however,
gives proofs or even mentions cxperiments.

C. THE INGESTION OF FOOD IN THE FRESH- WATER

SPONCIES.

Precediug: Researches. — The question of the ingestion of
food is closely related 'to that of the water-current ; therefore
the investigators have usually studied them together.

When studying this problem one should discern the ingestion
of solid food from the feeding upon substances in sohition in the
w^ater.

According to Putter (48, 49) 1909 and 1914, it would be
absolutely impossible that a sponge feeds on solid food only; on
the contrary, it would be more likely that it feeds on organic
substances in solution, which would be present in the water in
(relatively) large quantities and would diffuse through its surface
into its tissues. I shall not speak now about the — to my
opinion exact — critic on Pütter's theory by Biedermann (6)
and LiPSCHÜTZ (40). I myself have never found a proof of its
exactness during my investigations ; on the contrary, the argu-
ment on which this theory its based (the deficit of solid food)
seems rather not binding for the (green) fresh-water sponges —
see pag. 96. But, of course, I do not think the possibility
entirely excluded, that a sponge absorbs also feeding substances
in solution. Already Haeckel (25) 1872 thought this probable.
On the other hand, however, one certainly has no right to con-
sider the research of Loisel (41) 1898, who saw vital staining
Solutions taken up by sponge tissue, as a proof that sponges may
really take up feeding substances in solution, as Minchin (45) and
Sollas (53) do, and also Topsent (57) to a certain extent. For
we know from the researches of O verton (1902) that, although

i:}9

a ccrtaiii nuiiiljor of substances inay ciitcr a (;t'll l»y tlit!'usiii<5
(eg. the vital stains), a largo quautity of" otlior substanccs inay
iiot, and especially thoso, that might bo food to the cell. This
entering or not-entering would in tliis case bo a physical plicno-
menon, independent of the activity of tlie cell (lipoid-theory of
Overton). Although we are obliged, as IIöber (30) 1911 points
out rightly, to admit beside this pliysical permeability still a
physiological permeability of the cells, in order to make the ab-
sorption of nutriment (in solution) conceivable, we may never
consider the absorption of vital stains by cells as a proof to the
possibility of also absorbing nutriment in solution.

The capturing of solid food is generally stated for sponges.
As to this, the view of Vosmaer and Pekelharing (62) 1898 is
almost generally acknowledged in literature, as I mentioned already
in the Introduction. These investigators showed once more and
by better proofs than the ethers, that the flagellated chambers
would be the chief „eating-organs" of the sponge.

These experiments were made in the following way : A Spon-
gilla or a Sycon, having been for some time in water with car-
mine or milk, was either immediately killed in 1 °l^ osmic acid
or placed back into pure water and killed afterwards. The sponges
were examined in sections or in maceration preparations. I will quote
herc the description given by Vosmaer and Pekelharing: „In
sponges which had been for half an liour to two hours in water

with carmine or milk we found a considerable quantity of

carmine in the choanocytes, while in the pinacocytes and in the
cells of the parenchyma particles were seen here and there, but

in a considorably smaller quantity than in the choanocytes

If the sponge had remained for hours (to 24 hours) in the car-
mine, there was more carmine in the cells of the parenchyma
than in the choanocytes. If, after a stay of many hours in car-
mine, the sponge was placed back into pure water for some hours,
the carmine was abundantly found in the cells of the parenchyma,
and hardly at all in the choanocytes. Feeding with milk had
about the same results we believe we are entitled to

140

say that tho choanocyt(3S really are the organs by wliich particles
suspended in the water, passing the canals, are captured and thus
brought into the tissue of the body".

It is a matter of course that Vosmaer and Pekelharing
concoived the mode of capturing food by the choanocytes in
perfect agreement with their theory of the water-ciirrent, which
theory I mentioned at large on page 123 — 124. So the investigators
say: „The particles (suspended in the water) are.... transported
to the flagellated chambers ..... here the regular current at
once changes into a very irregular niövement" (as in Fig. 58&).
„The particles are moved to and fro in the chamber, and though
they partly leave the chamber through the apopyle, a number
will, however, arrive ivitJdn ') the collars of the choanocytes.
The protoplasm of the cells then seizes the particles in order to
give them off again to the cells of the parenchyma. This does
not prevent that now and then particles can be seized by cells lining
the canals; but this will always be of less importance. Met-
schnikoff's opinion that the flagellated chambers were not the

real „eating-organs" is not sufficiently supported by his

observations".

Thus runs the theory of Vosmaer and Pekelharing. Minchin
(45) 1900 holds a somewhat different view, namely that of
Metschnikoff (44) 1892. Although this theory of Metschnikoff
has been contested by several investigators — eg. by Yosmaer
and Pekelharing — and Biedermann (6) declares: „diese letz-

tere Bchauptung" (the Metschnikoff theory) „erfuhr keine

Stütze, indera sich herausstellte, dass die Kragenzellen wirklich
die einzigen direct nahrungsaufnohmenden Elemente sind", I
shall quote Minchin's words, as they become of importance by
the results of my research. Minchin says: „Although the problem
might seom a simple one, thcre is no question which has been

so much discussed as the nutrition of sponges With regard

to the ingestion of food two opposite opinions have prcvailed,
one set of investigators attributing an ingestive function to the

1) J talies from me, v. T.

141

collar cells, another set rcgarding the „mesodenn cells" as the
true phagocytes, Those wlio hold the formcr view cxplain the
presence of ingested particles in mosoderm cells as having passed
on to tliem by the collar cells. The true explanation seems to
lie, as Metschnikopf has pointed out, between these two opinions,
The „mesoderm" shows a great difference as regards its degree
of evolution in different types. While in some, eg. Ascons, tlie
parenchyma is scarcely developed, in ethers it reaches a high
grade of complication. In accordance with these differences the
part played by the parenchyma in capturing food may, in some
cases, be very slight, in others very great. There can be no
doubt whatever, from numerous experiments that have been per-
formed by various investigators from Carter and Lieberkühn
in the fifties up to Yosmaer and Pekelharing at the present
time, that in many sponges at least the collar cells are very
active in capturing food. On the other hand, these cells are from
their nature and size incapable of ingesting large bodies such as
Infusoria or Diatoms, Food of the latter kind could only be
absorbed by becoming entangled in the webs of tissue in the
incurrent canal system, there to be absorbed by the phagocytic
wandering cells, or, it may be, by porocytes".

„Considered generally, sponges present a gradual evolution as
regards the power of ingesting food materials, corresponding to
the evolution of the canal system. In the simplest ferms, such
as Ascons, microscopic food particles are ingested by the collar
cells ; larger bodies, such as diatoms may be captured by the
porocytes, which close upon them like a trap when they enter
the intracellular lumen of the pore. The collar cells represent
however the chief „eating organ" of the sponge".

„In other sponges the complications of the incurrent system
represent a progressive elaboration and perfection of an apparatus
for assimilation, doubtless, in the first instance, of bodies too
large to be absorbed by the collar cells. As the water passes
through the inhalant canals and spaces, food in it is captured
by cells in the parenchyma, either by phagocytic amoebocytes
or, perhaps, also by porocytes. The function of ingestion may

142

finally be usurped almost entirely by cells in the parenchyma;
the collar cells then become concerned only with the produetion
of the current, their ingestive activities being in abeyance (Met-
schnikoff)."

Thus MiNCHiN. Finally I will just mention what Cotte (12)
1902 says about the mode of ingestion of food by the choano-
cytes: „je suis disposé a croire que..,, l'ingestion peut se faire
par toute la surface de la cellule active". But further: „L'inges-
tion parait se faire généralement dans une espace annulaire situé
entre Ie flagellum et la collerette". And „Le seul róle que nous
puissions actuellement prêter (aux coUerettes) en dehors d'une
intervention active dans les faits de phagocytose, est celui de
guider les particules alimentaires vers la base du flagellum, point
oü la phagocytose parait se faire avec le plus d'énergie".

Persoiial Research. — The 4 principal questions^ wkich I
sïiall have to treat, are therefore: P^ Are the food particles cap-
tured froni the water bi/ means of the choanocytes of the fagel-
lated chambers? 2'^^, Jn wJiat ivay does this capture by the choano-
cytes taJce pjïace? 3''^ What happe^is to the particles captured?
4^^ Does the sponge disp)0se of still other means of capturing fioating
particles from the water?

I have been able to answer these 4 questions, ainong others by
observing my normally living inicroscopic p)reparatio7is of sponge
tissue (p. 12 — 13). I therefore placed these preparations in water
from the conduit, to which I added some carmine, or in a very
dilutcd suspension of green symbiotic algae isolated from another
sponge. To make the observation succeed, it is necessary to trans-
port the preparations already some hours in advance into the
glass vessel (with the suspension) finally used for microscopising,
otherwise one never sees the capturing of the particles; for, pro-
bably, the ostia remain closed after the transport of the sponges,
to be opcnod only after some time, so that only then the normal
water-circulation starts. The phenomena can never be observed
so beautifully with a suspension of symbiotic algae as with a'
carmine suspension.

143

It goos without saying, after the results obtained by Vosmaer
and Pekelharing with carmine-feeding to Spongillae, that I too
found the first questionQ,^vm?d\yG[j Q,ri.^yi2VQè.'. The particles fioating
hl the ivater are captm'ed in a mass hy the choanocytes of the
fayellated chambers; very often their layer is dyed quite red by
it (in case of carmine nutrition). It also stands to reason that,
since I had stated a mode of motion of the flagella and the water
within the flagellated chambers quite different from that described
by both the investigators mentioned, also the way in ivhich the
choanocytes capture the foocl particles was bound to prove wholly
diiferent: those particles are not captured inside the collars at all^
as Vosmaer and Pekelharing thought, hut on the contrary out-
side-hetiveen the collars (especially at their base) or betiveen the
bodies of the choanocytes themselves. That this must necessarily
be the case, immediately appears from Fig. 55, 59 and from Fig. 63,
the diagrammatic representation of the water current in a flagel-
lated chamber as the resultant of the streamlets produced by
each flagellum separately. For the bodies and collars of the choano-
cytes must^ so to say, filter the water, circidating between them,
free from fioating particles.

I shall now give a description of the capturing of carmine, as
I have been able to observe so many times in my living sponge
preparations. So the little sponge is in carmine suspension under
oil immersion in an Engelmann case ; one has selected a favourably
situated flagellated chamber.

It is beautifully to be seen how the carmine is captured ! Con-
tinually grains run on rather rapidly to the flagellated chamber,
carried along by the water in the incurrent canal ; they slip into
the prosopyle, but then they are either immediately kept or first
they move quickly a little aside into the choanocytic layer, and
stick there. On more accurate observation, however, the grains,
after entering the prosopyles, prove in most cases to slip through
the choanocytic layer, but, when having got to the base of the
collars, to suddenly deviate aside and to be soon captured — still
at the bases of the collars. Only very seldom a grain penetrates
any farther, in the zone of the collars themselves ; as most of

144

them have been captured in advance, eitlier between the bodies
of the choanocytes or between the bases of the collars. ïhe
movement of the flagclla is always the rapid spiral- or undulating-
motion, which was mentioned above as the normal one; the col-
lars are normal, far extended.

These different ways of capturing carmine grains are represented
in Fig. 05^ 66. In both figures the choanocytic layer is drawn
for convenience's sake as a broad circle; and the way taken by
the grains is indicated by dots; while in the last figure — drawn
from nature — the choanocytic layer has been represented as
loaded with carmine.

After all I have said and drawn about the structure and the
water-current of the flagellated chambers (p. 132—134, Fig. 55,
59, 63), the here described way of capturing carmine between
the choanocytes — by which the water circulatiug in a chamber
is so to say filtered — is quite intelligible. I only want to point
out that the phenomenon, that the carmine grains generally
immediately pass the choanocytic layer, but then suddenly
deviate aside along the base of the collars to be kept there,
can be explained by the fact that in a living chamber on the
one side the bodies of the choanocytes are shorter and bigger
— which makes the open spaces between the separate cell
bodies much smaller — than has been represented in Fig. 55 and
in the diagrammatic Fig. 63, while on the other side the
collars are approaching each other more and more in the direction
of the centre of the chamber. In other words : the flowing
water will find the widest passage in a chamber exactly at the
bases of the collars (compare Fig. 59). Therefore, however,
one should not think that zone of the bases to be extremely
unfit for capturing floating particles ; that only depends upon
the relative size of the latter. ïhe carmine grains now are ^ —
1 /y., the symbiotic algae 2 — 3 ^; thus so small that they can
just pass the prosopyles, while they will stick between the bases
of the collars. The more so, as we may suppose that the collar
cells, for the advancement of that purpose, will be provided with
a stick y, mucous surfaco, as is also accepted for protozoa.

145

Many times I have observed this phenomcnon of carmine cap-
turing, in different preparations during several years (1915, '16
and '17); it always took place in the way described here. I had
also the opportunity of demonstrating it to Professor Vosmaer and
Professor Pekelharing ; both held my conception convincingly
proved by the living preparations.

In exactly the same way as described now for carmine, I have
also observed several times green symbiotic algae being captured
by the choanocytes in a chamber.

As mentioned before, only very seldom a carmine grain gets
into the zone of the coUars, as most of them have generally been
captured already in advance. If it does take place, howevcr, it
is the collars which prevent their escaping. For these appear to
be very active enlargements of the capturing-surface of the choano-
cytes, as the particles which might have escaped from their cell-
bodies or collar-bases are, in most cases, held between the long
collars, as I have been able to observe. A representation of such
a case is to be seen in Fig. 67, a carmine grain which I saw
captured between 3 collars (seen from above). Afterwards one
can see the grain slowly descending along a collar to the base.
(Fig. 68, 1-2). I saw the same thing happen to green' symbiotic algae.

So here we have stated the remarkable fact^ that the choanocytes
capture the food particles in exactly the same ivay as the Choano-
flagellata.

Only very rarely a carmine grain quite succeeds in escaping
from the collar cells; then one sees it slip through the chamber.
Sometiraes also, the way, gone by a grain in the chamber be-
fore being captured, seems different from the normal one; an
explanation might be given for it, but cannot be proved.

Now the prosopyles still need treating. They are generally not
to be distinguished, even if one sees the carmine grains enter
the flagellated chamber at a certain point; and no wonder. For
one does not see the separate collar-cells either, but only their
joined layer as a whole. So it may count as a peculiarity, that
there were even two prosopyles to be distinguished in the chamber
of Fig. 66. The left one was varying in width; I measured it as

10

146

7 — 8 [y. on an average. The right one, on the contrary, was more
normal viz. narrower, with the ordinary width of 3 — 4 ^ot, and
constant as to size. Further, I think to have observed once a
great change of a prosopyle of another chamber, viz. that it
narrowed from an at first long, rather wide fissure to an opening
of 4 //-. Taken for itself this seems a queer observation, rather to
be explained by optical delusion. But it deserves our attention,
when one considers it in connection with the preceding and with
what Delage (15) says about the prosopyles of Ephydatia: „méats
intercellulaires de grandeur et de forme extrêmement variables,
produits par écartement peut-être temporaire des cellules flagel-
lées pour donner acces a l'eau", while also Weltner (65) writes
that they can arise and disappear again. In fact, this would be
logical; as in that way a flagellated chamber, after the choano-
cytes near the existing prosopyles had been overloaded with par-
ticles from the water, could open quite new prosopyles simply
by separating some other choanocytes.

Finally I want to remind, that all these experiments with the
normally living microscopic preparations could only be made with
tissue of Spongilla (as Ephydatia grows so very slowly).

I now must ansiver the 3''^ questioti, namehj what haj^pens to
the particles from the water ^ after they have heen captured by the
choanocytes at the base of the collars.

Those particles — carmine grains or symbiotic algae — are
then taken up by the protoplasm of the choanocytes and carried
along into the cell (Fig. 66). How, I have never been able to
observe ; but one sees them enter the choanocytic layer ; while
one also sees ^hem very distinctly, either in intact flagellated
chambers or in isolated choanocytes, within the separate cells
and always free in the protoplasm, never enclosed in a vacuole.

Next those particles are rather soon ejected by the collar cells
ayain into the surroundiny tissue — let me say here, into the
yfintercellular jjlasmic groundsubstance^\ in which also the chloro-
phyll carrying amoebocytes are to be found (chap. F.) — from
whence those amoebocytes take them. later on. This fully corresponds

147

to the results of Vosmaer and Pekelharing (p. 139 — 140). I have
been able to observe it several times in my living preparations,
regarding symbiotic algae as well as carmine.

A description may follow here. Fig. 69 represents a fiagellated
chamber with its normal surroundings of „intercellular" substauce
and amoebocytes (the figure has been drawn true from nature).
The shuttle-shaped amoebocytes with the green algae continually
slide in various processions -- often directed oppositely (see
arrows) — past the chamber ; no canals are to be seen. The
flagella show the normal rapid spiral- or undulating-motion. In the
choanocytic layer a number of green symbiotic algae are lying
together at the base, in groups of 5 — 15; sometimes such a
group is to be found in a protrusion of this layer (Fig. : 1). There
all at once, in less than no time, the algae of that group are
lying outside the layer, free in the „intercellular" space, but
still on their original place (Fig. : 2). So the protrusion of the
choanocytes must have been with drawn and must have „left
behind" the algae. At least in this way one should explain the
phenomenon, that has such an exceedingly rapid course. Next the
algae, which got free in this manner, are slowly spread all over
the „intercellular" substance (Fig.: 5), from where the amoebo-
cytes will be able to take them up at t"heir desire. That, in fact,
the amoebocytes do so, will appear from a following observation.

But first I will describe another flagellated chamber in a prepara-
tion, in carmine suspension. Situation almost as in the preceding
figure, though here canals are ta be seen. Here is to be observed
very distinctly how the carmine is ejected into the parenchyma
(Fig. 70, I — III ; from nature) ; namely two small grains (a and b)
ejected one after the other from a protrusion of the choanocytic
layer. The figures speak for themselves ; in I the original condi-
tion is given ; in II the successive removals of grain a, after it
has been expelled, are indicated by 1 — 5; and in III the same
is given for grain b. Here the ejecting takes place into a very
plastic tissue-bridge.

Then a flagellated chamber overloaded with carmine in the
same preparation (Fig. 71, true from nature), while the carmine

148

from the chamber as centre begins to spread through the „inter-
celhilar" substance by little streamlets moving to and fro. The
flagella are in rapid spiral- or undiüating-motion. In the choano-
cytic layer the small carmine grains are united at the base into
conglomerates, just as we saw already for the algae ; while also
outside the chamber in the tissue the conglomerates are more
numerous than the separate grains (Fig.). Already some amoebo-
cytes in the neighbourhood have taken up carmine. This must be
originating from the choanocytes and have been taken from the
„intercellular" substance, as there is nowhere any carmine to
be seen in the whole preparation, except in 6 flagellated cham-
bers with their nearest surrounding. Now, after the preparation
has been in pure water all night, the next morning the above
mentioned chambers are almost without carmine; but in the
surrounding there are many carmine conglomerates, sometimes
still free in the „intercellular" substance, most often however
situated within the amoebocytes with algae (and then by times
within a vacuole).

The here described phenomena of taking up carmine or algae
within the choanocytic layer, foliowed by ejecting into the „in-
tercellular" plasmic substance and being taken up again by the
amoebocytes with green algae, have been studied by me several
times, although not in all their minor subdivisions ; and this not
only by observing normally living preparations of sponge-tissue,
but also with the aid of ravel preparations.

One might now ask what happens to the particles captured,
after they have got within the amoebocytes with symbiotic algae.
I shall postpone this question to the next chapter, to first answer
the last question of p. 142.

Does the sponge dispose of still other means of capturing fioat-
ing particles from the water? I have been able to answer this
question affirmatively* again by observation of my normally living
microscopic preparations. The phenomenon, however, is very dif-
ficult to observe, as a number of favourable conditions must be
realized togother — which only happens very scldom. It was not

149

until I had obtained in another way the proofs, that there should
still exist in the sponge an entirely different method of capturing
food, that I succeeded iu observing it in my living preparations.
Those proofs were in short:

1. If one makes a ravel preparation of a little sponge (Spon-
gilla or Ephydatia) that has been in a suspension of carmine or
symbiotic algae for some hours — and thereby has become light-
red or light-green — , then under the microscope the carmine or
the algae prove to be present:

a. in a great quantity of course in the choanocytes of the fla-
gellated chambers.

h. little or not yet in the amoebocytes with symbiotic algae —
for the transport from the choanocytes to these amoebocytes
takes time.

c. in a relatively great quantity in a not very numerous kind
of amoeboid cells, which distiuguish themselves from the
ordinary amoebocytes with symbiotic algae by their gene-
rally almost entire lack of such algae, while sometimes
they hold all sorts of detritus (by tinies situated in vacuole).
Their nucleus is, as that of the amoebocytes, vesicular.

2. While now in the choanocytes the carmine generally occurs
as small grains or as conglomerates of sniall grains, it appears
to be present in the cells, mentioued under e, principally in big
grains or their conglomerates. (Perhaps one w\\\ doubt, if car-
mine grains and conglomerates are so easy to be distinguished.
In fact this is the case: the grains are generally simplc in out-
line, straight and angular, as pieces of a crystal, and internally
homogeneous, refractive red ; while the conglomerates are appa-
rently more rounded oif, but in reality more irregular by num-
bers of re-entering angles, and internally not homogeneous but
red, every where interrupted by black ; which is conceivable by
their structure.)

3. Very often one can clearly see in a normally living mi-
croscopic preparation, which has been in carmine suspension for
some hours already, that the carmine, except in the choanocytic
layer of the flagellated chambers, is also to be found in mass in

150

an apparently iindifferentiated plasmic substance (in which few
or no symbiotic algae) lining the canals. A lively transport of
carmine takes place there. By itself this does not say anything ;
that carmine could be proceeding from the flagellated chambers,
though then it would be rather peculiar that it should exclusi-
vely extend along the canal walls. Sometimes, however, it also
appears that there is a certain difference in size between the
carmine grains (not conglomerates !) within the choanocytes and
those in the canal walls. The former are almost exclusively small
(0.5 — 0.7 f/,), those in the walls often much larger (1.5 — 4 f/.).
This fact now is supported and completed in a very desirable
manner by what we could state above under 2 in ravel prepa-
rations.

The 3 points mentioned sufficiently indicated, that in a sponge
had to he still qiiite a different method of capturing food-partides
— and especially coarse parücles — ; and such in the canals
themselves, outside the flagellated chambers; for wich then, of course,
only the incurrent canals had to he considered. By chance I dis-
covered that method; though, after all, one must say that it had
to be functioning in a sponge.

Just think of the structure of the canalsystem : incurrent canals —
flagellated chamber — excurrent canals. One always used to say that
the narrow ostia (dermal-pores), placed at the entrance of the
incurrent canals, prevent the too large particles floating in the
water from entering, and so from blocking up the canal system.
But these ostia measure in living Spongillae, as I have been able
to state several times, even to 63 X 84 |C^, while Delage (14,15)
could fix their width in killed Ephydatiae on 6 — 30/^. Now,
generally the prosopyles only measure, as we saw, 3 — 4 jCc. So it
goes without saying that numbers of particles will enter by the
ostia, which are too large to pass the prosopyles. What must hap-
pen to these particles, what must the sponge do with them, when
they have come with the water-current to a flagellated chamber
and remain sticking in a prosopyle, so stop it up? They must
be removed, otherwise — in nature there are so many particles
in the water — the sponge would unavoidably die within short.

151

by all its prosopyles being stopped up. Of course tlio sponge can-
not do it in any otlier way tlian by constantly making itself master
of those particles, by taking them up within its cells, witliin its
tissues, with the help of protoplasm currcnt ; in order to push
them out again afterwards (about this in another chapter (E)).

Now, in fact I have observed this phenomenon several times
in my normally living microscopic preparations.

It is knov^n, that a choanocytic layer of a flagellated chamber
is covered with a thin tissue layer at the side of the incurrent
canal. I refer to the figures of the different authors: eg. Delage
(14, 16), MiNCHiN (45), VosMAER (59, 62) a. s. o.

I myself observed in my living preparations, that outside and
against the flagellated chamber at the side of the incurrent canal,
against the base of the choanocytes, there is a thin layer of
apparently undifferentiated protoplasm, which one time is relatively
thick (1 — 'ó y.) and thus easily to be recognized as being separated
from the choanocytes (and of course from the lumen of the canal),
but next time is so thin, that it appears as a whole with the
choanocytic layer. Symbiotic algae occur but few in it, or not at
all. That layer, which one must imagine to be covering more or
less the whole prosopylar side of the chamber (except of course
the prosopyles), appears to be simply a continuation of the lining
of the incurrent canal extending over the flagellated chamber,
and, when visible, distinguishes itself from the choanocytic layer
by a lighter tint (and of course by a darker one from the lumen
of the canal). In that plasmic layer, now, very of ten all sorts of
particles — : eg. oildroplets '), or carmine grains if the prepa-
ration is in a carmine suspension — are carried on slowly by
protoplasm current and are so removed over considerable distances
(eg. '/^ of the outer surface of a flagellated chamber) -). Thus
it is seen, for instance, that by this current carmine particles are
carried off aside of the chamber into the parenchyma. All this
is given in Fig. 72 — 74, which have been drawn from life. (In

1) One rernembers that, as mentioned on p. 100, those oildroplets would be the
source of the encrgy in the flagellated charabers.

2) By which a plasmic layer, which is uot visible by itself, may bc recognized.

152

Fig. 74 one also sees the transport of carmine along a little
„bridge" bent through a canal; cnf. Fig. 70).

That this layer of flowing plasm must exist on the incurrent-
canal-side of a chamber, is again very logical. For what would
the choanocytes, eg. in Fig. 73, do with their captured carmine,
if that layer was not there?

Many times I have observed this layer on a chamber. I have
also had the opportunity to demonstrate it to Professor Vosmaer
and Professor Pekelharing.

The rest of my observation concerned: A flagellated chamber
with much carmine in the choanocytes already ; carmine grains
run up through the incurrent canal and enter by a prosopyle.
There approaches a large carmine ball (7x8 [x), also runs
towards the prosopyle, but remains sticking in it. During 10
minutes nothing is seen to happen; but then the ball is going
to move and it is, along the outside of the chamber — so
between chamber and incurrent canal — , very s 1 ow 1 y — as by
protoplasm current — carried off aside into the tissue
over a distance of more than 18//. A moment later a similar
phenomenon is to be observed on a somewhat smaller carmine
ball, at another prosopyle of the same chamber. I also observed
exactly the same thing happen to an alga and to a protozoon in
other similar preparations.

So it is the layer of apparently undifferentiated -flowing plasma^
situated outside and against the flagellated chamber at the side
of the incurrent canal, that tahes up these big particles —
which, carried along by the current of ivater, got into or against
the prosopjyles and threaten to stop them up permanently — and
that carries them off into the tissue, so that the prosopyles again
become accessible (Fig. 75). If these particles might be of any
use to the sponge as food, this u-ill undoiibtedly keep them and
carry them to the amoebocytes (and digest them); which, as we
saw already, also happens to the particles captured by the choano-
cytes. If they are of no value to the sponge, this will try to get
rid of them as soon as possible. More about this later on.

153

If one now inquires after tlie morphological meaning of this
layer of apparently undifforentiated flowing plasma, I must declare
that for this moment I don't dispose of sufficiënt data to answer
this question (but see Appendix). Considering the above mentioned
(p. 149 sub 1 6'), one is inclined to look upon it as consisting of
amoeboid cells (one or more for each flagellated chamber). But
one should not forget that that state mentioned of the sponge,
tested as ravel preparation, answers to what we got to know as
the state of the normal intact sponge on p. 149 sub 3. There it
proved that the canal walls in general, not especially the exterior
covering of the flagellated chambers, were loaded with carmine.
So it is quite possible that the amoeboid cells, treated on p. 149
sub 1 c, have simply been canal-wall-cells, and have not had anything
to do with that covering. The same counts for what follows.

I killed a living sponge preparation, that, according to obser-
vation, had reached in a carmine suspension a stage as given on
p. 149 sub 3, in osmic acid and afterwards had the tissue mace-
rated in water, to finally study the separate cells under the
microscope. ïhe carmine now proved to be present: l^t in a great
number and in fine grains within the choanocytes 2°'i in a great
number and in big grains or conglomerates within very irregu-
larly branched amoeboid cells. These amoeboid cells can take the
most simple up to the most fantastic shapes ; one sees isolatcd
cells with long and broad protrusions, even extended to mem-
branes or stretched as bands (of course all pseudopodial processes),
exactly as was observed in living preparations as the apparently
undifforentiated plasmic substance; one sees cells with the ap-
pearance of a hollow tube, which evidently lined a canal, with
plasmic „bridges" and even membranes extended in the lumen.
All of them contain carmine. These amoeboid cells now carry
an often clearly visible nucleus, little or no symbiotic algae and
sometimes detritus ; they are rather numerous. But carmine is
hardly ever to be found in the ordinary amoebocytes with a great
number of symbiotic algae.

One sees the striking conformity with what was found on
p. 149 sub 1, 2, 3. So the apparently undifforentiated plasma lining

154

the canals, which lodges the big carmine grains, does belong to
amoeboid cells. Perhaps one is now inclined to look upon these
as being pinacocytes, because in general the canals are supposed
to be lined by this sort of cells — see eg. Delage 14. But,
probably, the latter is not right for Spongillidae ; a fact which
Weltner (67) pointed out already, and which I too could state.
I namely found the canals lined : here by flat pinacocytes ,
there by amoebocytes with symbiotic algae, yonder again by
apparently undifferentiated plasmic substance (Fig. 71). (Or must
one, in both last cases, imagine the pinacocytes to be present,
but extended so thin that they escape to our sight?) As the
pinacocytes, moreover, generally do not show such an irregular shape
(as the carmine-carrying cells in the above mentioned macerated
material) and as they usually are also easily to be recognized
as cells in a living preparation (while here we are speaking of
apparently undiff'erentiated plasma), one had better explain this
plasma, these amoeboid cells, as belonging to the parenchyma,
which then is not lined here by pinacocytes — or by very thin,
not separately visible pinacocytes? — . I will return to this sub-
ject in the Appendix.

At any rate the mentioned apparently undifferentiated plasma
belongs to amoeboid cells. But, as said, one may not yet con-
clude from this, that the flowing plasmic layer at the exterior
of the flagellated chambers also belongs to amoeboid cells. If,
however, this was in fact the case, we could ascribe several
morphülogical meanings to those cells. In the first place one would
be inclined to look upon this layer as being pinacocytes again
or better parenchyma lined with thin pinacocytes — as Delage
(14) gives — or parenchyma without pinacocytes. On the other
side, however, one might say that here we had amoeboid cells,
which probably entirely surround the prosopyles of the chambers,
in other words, something as the well known porocytes of cal-
careous sponges. I will also return to this question in the
Appendix.

For the rest, the whole question of the morphological meaning
of the apparently undifferentiated plasma of the canal walls only

155

stands in a distant relation to the problom, wc are trcating just
now, tlio ingestion of food.

Which of the two methods of capturing food, the one with
the choanocytes or the one with the plasmic layer, is the most
important one for the sponge, will depend, in my opinion, simply
on the size of the food-particles present. If the size is small the
l8t, if it is larger, then the 2"'! method preponderates, With
carmine nutrition the capturing by choanocytes was the chief one.

Finally one might ask, if the sponge can capture food in still
more ways. I must answer that I think it quite possible. In the
first place I think of capturing particles in the incurrent canals
themselves, which show all sorts of irregular lumina, while fine
plasmic bridges, sieve-like membranes and what not, are extended
in them, so that they have plenty of opportunity of capturing.
Also ingestion of food at the outer-surface of the sponge seems
possible. I have, however, never observed these ways of capturing.
One thing would prove against them, viz. that with a carmine
nutrition of short duration there is hardly ever carmine to be
found anywhere else in the sponge than just in and at a short
distance from flagellated chambers, as I often stated. But I have
also made observations which are in favour of* them.

In a living preparation there were numerous Flagellata moving
quickly within the canals and at the outside of the sponge. Such
organisms, now, some together and sometimes with carmine
grains, were also moving within small vacuoles in the canal-walls
or in the tissue at the outer-surface. It is quite impossible that
these living organisms have been captured by the choanocytes or
the plasmic layer; for then they would have been killed, at least
they would be motionless. They are more likely to have been
captured after having arrived in a blind ending part of the canal,
the latter partly narrowing — for the tissue is very plastic, the
canals arise and disappear while one observes them — and closing,
when lts size had been reduced to that of a vacuole ; while finally

156

a cell took up the remaining vacuole with the Flagellata in it.
At least, one can explain the phenomenon in this way.

Sometimes one also finds diatoms in the sponge tissue, which are
too large to have been ingested by choanocytes and perhaps also
by the plasmic layer. These are more likely to have been captured
by the tissue bridges and sieve-like membranes of the canals.

Finally there must necessarily exist a system at the ostia to
remove the too large particles kept there, so those which may
not enter the incurrent canals ; this need not be accompanied
with taking up within the cells. On the other hand, however,
it is difficult to think, that food captured in that way should be
of no use at all. So here might be still another means of capturing
nourishment. I have never seen anything of it.

So we saw in tJiis chapter tliat in the fresh-water sponges:
pt the small (food-) particles are captured from the circulating
water within the fiagellated chainbers-, viz. outside-between the col-
lars (especially at their base) or between the bodies of the choano-
cytes^ ivhile thus, so to sag^ the water is filtered clear (Fig. 63^
65 — 68). Next these particles are taken up within the choanocytes^
united to conglomerates and ejected again into the ^intercellular"
plasmic groundsubstance (Fig. 66, 69 — 71), from whence the amoe-
bocytes with symbiotic algae take them up in their turn (Fig. 71).
2^'^^ the coarse (food-) particles are captured from the circulating
water outside and against the fiagellated chambers at the side of
the incurrent canal, and such, because they remain sticking in or
against the prosopyles. The thin layer of apparently undifferent-
iated floiving protoplasm, which covers that side of every fiagel-
lated chamber with the exception of the prosopyles (Fig. 72 — 74),
then takes up each partiele and carries it off aside into the tissue,
so that the prosopyles again become accessible (Fig. 75). If these
particles may be of cmy use to the sponge as food, it is very likely
that they are carried on to the amoebocytes with symbiotic algae,
just as those captured by the choanocytes.

So we see that it is not right, when Biedermann (6) declares

157

„dass die Kragenzellen wirklich die einzigen direct nahrungs-
aufnehmende Elemente sind".

While on the other hand Minchin (45) wrote rightly : „There
can be nö doubt whatever, .... that in many sponges at least
the collar cells are very active in capturing food. On the other
hand, these cells are from their nature and size incapable of in-
gesting large bodies such as Infusoria or Diatoms. Food of the
latter kind could only be absorbed by becoming entangled in the
webs of tissue in the incurrent canal system, there to be absorbed
by phagocytic wandering cells, or, it may be, by porocytes".
Especially this last supposition, the ingestion by porocytes (here =
plasmic layer, p. 154), has proved to be exact.

D. THE DIGESTION OF FOOD IN THE FRESH-WATER

SPONGES.

I shall be quite short about this subject, as I only possess
very few other data concerning it, except all I told above in
extenso about the digestion of the green symbiotic algae in the
sponge tissue, under the head „Chlorophyll" (p. 16 — 17, 42 — 45,
94—116).

As we have seen, however, (p. 96) that exactly the symbiotic
algae are a very important, perhaps even the chief source of
nourishment for the fresh-water sponges, we certainly may con-
sider. the results, regarding their digestion, to be decisive with
regard to the problem of the digestion in the fresh-water sponges
in general.

We saw that the symbiotic algae, which the sponge has cap-
tured from the water in the ways described in the preceding
chapter and carried on to the amoebocytes, die within those
amoebocytes, either for a part, or all of them, and are digested
there and dissolved, while the decomposition-products come to the
benefit of the sponge (p. 111 — 113). This digesting and dissol-
ving mostly took place free in the protoplasm of the lodging
cells, sometimes however within a vacuole (p. 97). As I remarked

158

already before (p. 97), botli these methods of digesting are pro-
bably not different in principle, but only in quantity of secerned
enzyme (in other words, in rapidity).

I made no investigations into the enzymes acting (p. 96),
except that the presence of a lipase was made probable (p. 89,
98—99). Perhaps I will have the opportunity later on to extend
my investigation in this direction.

As for the carmine captured by the sponge, I can mention
thaty. after it had got into the amoebocytes with symbiotic algae,
jt was generally soon ejected by these again and removed out of
the sponge body afterwards — about which in the next chapter.
Only very seldom I have been able to observe a beginning of
digestion, a solution of the carmine; but then also, very remark-
able indeed, a solution was to be distinguished within a vacuole
(this became entirely light-red) from a solution quite free in the
protoplasm of an amoebocyte, in which case from the carmine
grain as centre the red colour slowly spread through the plasma.
In fact a nice illustration of what I have so often mentioned for
the symbiotic algae as plasma and vacuole digestion. A proof
now, that indeed the difference is a matter of rapidity (of digest-
ion), is given in these observations of carmine-solution in the
fact, that carmine grains were never to be found any more in a
light-red vacuole, on the contrary there were, when the solution
took place free in the protoplasm.

I obtained no data concerning a possible digestion of food else-
where, eg. in the „intercellular" spaces of the parenchyma.

This about the digestion of food. It had already been acknow-
ledged in literature [see among others Biedermann (6) and also
CoTTE (13)] that especially the amoebocytes took part in it.

E. THE DEFECATION AND EXCRETION IN THE
FRESH-WATER SPONGES.

Also these phenomena I have observed in my living prepara-
tions of sponge tissue.

On the whole, there is but little known for certain in litera-

159

ture about these processes. In the first place one lias of course
always thought probable the excretion of dissolved matter by
diffusion (see Burian (10) 1910) all over the inner or outer sur-
face of the sponge, though in fact no one has ever mentioned
any strong proof for it. On the other hand Haeckel (25) 1872,
Lendenfeld (36) 1883, Weltner (65) 1891 and Delage and
Hérouard (16) 1899 supposed defecation and (or) excretion as
being performed by the choanocytes; while Minchin (45) 1900
ascribes this function for a considerable part to the amoebocytes,
Bidder (5) 1892, on the contrary, to the porocytes, and Loisel
(41) 1898 tbinks the excretion being performed by the coutraction
of the mesogloea (ground-substance).

None of these investigators, however, mentions a definite ob-
servation of the phenomena. On the contary the following do:

Masterman (42) 1894 found, if a sponge (Grantia compressa),
after having been for some minutes in a carmine suspension
and afterwards in pure water, had been killed with osraic acid,
that amoeboid cells filled with carmine protruded from the ex-
ternal surface, as if they weré just going to be ejected. While
something the like seenied to have happened also at the internal
surface, as there were cells, ejected and laden with carmine, to
be found inside the canals too. Masterman says: „We have
here an example of a process of intracellular excretion for the
removal of waste solids".

Also the opinion of Cotte (13) 1904 is partly founded on
observation; as far as I know it is the last extensive publication
about excretion in sponges. As summary he gives: „Les cellules
mésogléiques (amibocytes, spongoblastes, etc.) rejettent leurs pro-
duits de désassimilation, sous forme de sphérules, dans la sub-
stance interstitielle qui les expulse graduellemement. Les sphé-
rules usées des cellules sphéruleuses clasmatosées sont expulsées
par la substance fondamentale ; un certain nombre de sphéru-
leuses vont s'éliminer d'elles-mêmes an niveau des canaux. Les
choanocytes excrètent directement dans Iqs chambres". This about
the excretion, about defecation: „Après l'ingestion de produits
inertes les chaonocytes rejettent dans les chambres une grande

160

quantité de ceux-ci. Les cellules sphéruleuses entrainent dans
leur élémination quelques-unes des particules qui ont été déver-
sées dans la substance fondamentale. La plus grande quantité de
celles-ci, après avoir été transportée dans tout l'organisme par
les amibocytes, est directement expulsée par la substance inter-
stitielle ; quelques-unes sont transportées jusqu'aux canaux par
les amibocytes qui les y rejettent". As far, however, as I can
gather from the description, Cotte has never observed the often
mentioned ejection of particles by the „substance interstitielle" ;
but he did observe the ejection of (or by) „cellules sphéruleuses"
into the canals, as well as defecation by choanocytes (within the
collar, just as in the Choanoflagellata !). Cotte experimented on
Reniera simulans and Sycandra raphanus.

As one sees, the whole problem of excretion and defecation is
still a long way from being solved ; particularly because so
often hypothesis and observation have been intermingled.

Noiv, jj» mijself have come to the conclusion, hy ohserving the
phenomena in my normally living microscopic lu^eparations of
sponge tissue^ that defecation — and very likely excretion at the
same time — takes place on a large scale hy means of vacuoles,
which occur along the tvalls of the (excurrent) canals in an ap-
parently undifferentiated plasmic substance^ that in reality con-
sists of amoeboid cells.

I now pass on to my experiments.

A proof, that defecation — so a process, by which solid par-
ticles captured from the water and food-rests, which are of no
use to the sponge, are removed from its tissues — is really
acting in the sponge-body, follows already from what I said in
the first part of this paper (p. 15 — 16). There we saw that a
sponge, newly caught from nature, has a dirty (green or brown)
colour, as its tissue is loadon with particles from the (also brownish)
water of the lake; this dirty tint, however, entirely disappears
and the bright (green or creamy white) colour comes in its place,
when the sponges have been cultivated for some days in pure

161

water from the conduit. Proof t/iat defecation must fake place
even on (i large scale. For with a microscopic obscrvation the
brown particles, which orginally werc in a great numbcr all over
the tissue, proved then to have almost disappeared. ïhe same
counts for colourless sponges which have captured siich a great
number of carmine grains from a suspension, that they have be-
come quite red ; here too the carmine is removed in pure water,
so that the sponges become colourless again ; while one finds the
ejected carmine conglomerates at the bottom of the culture- vessel.
Next I will mention that, just as I discovered the pheno-
menon of the capturing of coarse (food-) particles by (cells of)
the canal-walls for the first time in ravel preparations of sponge
tissue (p. 148 — -152), I obtained the first indications of the way
in which defecation takes place by means of the same pre-
parations :

As I mentioned on p. 149, one finds in a sponge (Spongilla
or Ephydatia), which has been in a carmine suspension for some
hours, a great number of carmine grains l^t in the choanocytes
and 2'^^ in amoeboid cells (without symbiotic algae but often
with all sorts of detritus), while on the contrary carmine is not
or rarely to be found in the amoebocytes with symbiotic algae.
Has the sponge been in pure water for some time after it got
out of the suspension, one finds, as was partly mentioned on
p. 146 — 148, only little carmine in the choanocytes, but now
much (as conglomerates, upto 4 pt large) in the amoebocytes with
symbiotic algae, while it is also to be found rather much, and then
in big conglomerates (upto 14 /y.), in amoeboid cells (present in
a small number) without symbiotic , algae but with (often) all
sorts of detritus. ïhe sponge itself then appears to be less red
than it was immediately after it came out of the carmine, while
now on the contrary the water, in which it has been, is coloured
slightly red. If the sponge remains in pure water for some days
more, one does not only find but little carmine in the choano-
cytes but also in the amoebocytes with symbiotic algae. The
carmine, however, is still present in a great quantity and in

large conglomerates in the often mentioned amoeboid cells with-

11

162

out, or with few, symbiotic algae, and then sometimes within
a vacuole. These cells, as said before, are not manifold ; they
lodge besides a vesicular nucleus (which is very much like
that of the ordinary amoebocytes) and the carmine eonglomerates,
also often all sorts of detritus and sometimes some unicellular,
green algae as described on p. 117, while a single time a va-
cuole has been formed round all these foreign parts together. I
believe, however, to have a reason for supposing that such vacuoles
'do occur more often in these cells round those parts than it
seems, but that then they are only temporarily invisible by the
accidental grouping of the particles. For I have noticed, that such
a vacuole entirely disappeared by a movement of the cell (so
that its contents seemed to be quite free in the protoplasm), to
become visible again a few moments later. Very often those fo-
reign particles are united to a more or less compact mass. Only
once I stated such a detritus mass being ejected by a vacuole
of an isolated cell.

In the mean time the sponge itself has lost very much of its
red colour in the pure water, while this now in its turn has
taken a red tint. As it proves that the sponge does not show
any destruction of tissue, we may explain the red tint in the
water as caused entirely by the carmine the sponge has (by way
of defecation) removed from its body. Now we examine the cul-
ture water ; then it appears that the following parts have sunk
to the bottom: carmine eonglomerates (eg. 7x10, 7 X 13 /C4.)
together with all sorts of detritus and sometimes a big unicel-
lular, green alga, which every time are united to more or less
compact masses, just as we found them above within the amoe-
boid sponge cells (without symbiotic algae). But there never was
an enveloping cell to be seen round these detritus-masses in the
culture water.

So here we have stated in ravel preparations^ that in the fresh-
water sponge the fimction of defecation is performed hy amoeboid
cells (with few or no symbiotic alyaej, ivhich hy means of vacuoles
fject the detritus masses outside the sponge tissue^ hut ivhich them-
selves remain within the tissue.

163

Tf one examines a normallij living prepm-ation of sponge tissue
that ' remains in carmine suspension for soms hours, one will find
carmino, as has been mentioned on p. 146 and 149 — 150, on the
one side in a great quantity in the choanocytic layer of the flagelr
lated chambers (Fig. 6G, 71) and on the other side also in a
great quantity in an apparently undifferentiated plasmic substance
(in which few or no symbiotic algae) in the walls of the canals —
to which it will have been transported, for instance, after having
been captured in the plasmic layer at the outside of the flagellated
chambers (p. 152, Fig. 75). 2'>J. If then the preparation is in pure
water for*some time, we find, as we saw on p. 146 — 148, hardly
any carmine in the choanoeytes ; but it now appears to be in
small conglomerates within the amoebocytes with symbiotic algae.
Besides we also find it in large conglomerates (upto 17 jot), and some-
times together with detritus, within vacuoles in the apparently
undifferentiated plasmic substance (in which few or no symbiotic
algae) situated along the canal walls. 3"i. The sponge having heen
in pure tvater for soine time longer, the carmine also disappears
from the amoebocytes ivith symbiotic algae, to he found almost only
as large conglomerates in an apparently undifferentiated plasmic
substance (in which few or no symbiotic algae) and mostly situated
along the canal walls and often together with detritus within a
vacuole (Fig. 76a, 77).

One will have to acknowledge that these observations on living
tissue correspond very well with the results obtained in ravel
preparations. The matter now ivas to observe the phenomenon of
the ejecting of feces itself.

In this too I succeeded in my normally living preparations.
But also here I had to exert much patience.

I shall now give a description of such a phenomenon of defeca-
tion, as I observed it on a preparation which, after having been
in carmine suspension, was in pure water for some time: A car-
mine conglomerate lies, together with some detritus and some
green symbiotic algae, along the wall of a canal in the
often mentioned apparently undifferentiated plasmic substance.
At first no vacuole is to be seen round these parts, but shortly

164

after there is; so then the carmine, the green algae and the
detritus are together within it. Now tJie vacuole is going to pro-
trude f ar into fJie canal (Fig, 76a); it is even pushed forward, so
to say^ on a hroad stem. All at once — one does not see how —
the verg thin vacuole ivall disajjj^ears at the side of the canal, some
small carmine -grains begin to loosen from the conglomerate, move
to and fro, a?id all of a sudden they run off; next some green
algae do tJie same (Fig. 76 b); and at last the large conglomerate,
moves a little to and fro, as if it ivere still kept back — then sud-
denly it runs off through the canal!

So one sees that here there is no question of the feces being
ejected together with the lodging cell, as Masterman says; the
cell, or tvhatever this apparently imdifferentiated plasma may be,
simply stays behind in the wall. I have observed this phenomenon
of defecation several times in the same way.

Let us now attentively examine such a feces conglomerate
before it is ejected. So it is in the apparently undifferentiated
plasmic substance within the tissue. Later on I shall speak about
this plasmic substance. Often no vacuole is to be seen around the
conglomerate at first ; this only appears later on and then increases
rapidly. One can also observe how, from all sides, small feces-
particles (being within vacuoles or not) are carried on to the large
conglomerate (also being within a vacuole or not) and are united
with it. In the mean time the conglomerate is continually carried
along in the tissue by the plasmic substance over considerable
distances, so that for instance it happens but too often, that it
escapes to our sight by disappearing into deeper tissue-layers. In
the same way one can see a conglomerate — then always within
a vacuole — moving repeatedly from one canal to the other;
while the vacuole often protrudes so far into the canal, that one
thinks it will burst ; but it withdraws again entirely into the tis-
sue and goes to another canal, to repeat the same. A remarkable
sight, which I want to describe somewhat more at large.

A normally living microscopic preparation of sponge tissue,
which has first been in carmine suspension and afterwards in
pure water. A large carmine conglomerate lies again in an ap-

165

parently undifferentiated plasma, between three canals (Fig. 77, 1) ;
there are some green symbiotic algac to bc foimd in the plasma,
but by no means so many as in the ordinary amoebocytes; no
vacuole present. A few moments later a vacuole arises around
the conglomerate, while at the same time also some green sym-
biotic algae are enclosed. The vacuole rapidly increases
and protrudes more than half way into the lumen of a canal
(Fig. 77, 2). But it does not burst! On the contrary, the vacuole
withdraws into the tissue, to protrude then into another canal
(Fig. 77, 3). But here it does not burst either, but withdraws
again. Now it lasts for some time. At last it protrudes into the
3''d canal (Fig. 77, 4). All at once the thin vacuole wall disap-
pears at the outside ; the conglomerate still remains in its place,
it only moves a little to and fro, as if it were still kept back,
then it slightly moves on and again to and fro, a pull — and it
runs off through the canal.

A remarkable process, that protruding into a canal, to withdraw
again after some time ! I have repeatedly observed it, as said
before. Why dit not the vacuole burst immediately?

The only answer I can give, based on my observations, makes
us acquainted — if it is right ~ with a remarkable phenome-
non of sponge-life, which, however, is very logical, even indis-
pensable. Just consider : The fecal cotiglomerates must necessa-
7'ily be ejected exclusively into the excurrent canals of the sponge^
otherwise the whole defecation-system would unavoidably fail.
As we saw, however, the vacuoles with the feces are not bound
to certain permanent places, but they are, just as the whole
sponge tissue is continually moving, always carried along. But how
does a vacuole „know" then if a canal is an incurrent one, in
which it may not eject its contents at all, or an excurrent one?
The vacuole — or better the protoplasm, to which the vacuole
belongs — must examine this on the spot and then it will show
the phenomenon which we saw it perform above: it will protude
into the canal. Thus the thin protoplasmic vacuole-wall will get
to know in some way or other the state of the canal, either, for
instance, by the rapidity of the current or by the pressure of

166

the water. If the right (excurrent) canal has been found, the
plasma contracts and the vacuole bursts ; if, however, it proves
to be an incurrent canal, the vacuole will withdraw to trj the
same somewhere else.

Now, my observation relative to this was in fact, that the
vacuoles withdrew from canals which, if it was possible to dis-
tinguish, proved to be incurrent canals. (One can distinguish it
from the situation of the flagellated chambers).

We now got to know the process of defecation, which, as we
saw, must very often take place in nature, where the water
contains so many particles, that the sponges have quite a dirty
tint, which however they soon lose in clean water (p. 160 — 161). This
defecation proved to take place by means of large vacuoles. These
vacuoles are partly filled with liquid — undoubtedly originating
from the sponge tissue — ; this liquid is ejected with the feces.
Have nof we found here, tlten^ besides a powerful defecation pro-
cess also a strongly acting excretion process? I think we have.

But we have not yet quite finished the process of defecation.
There exists, besides the liere described tvay of defecation everyivhere
at arbitrary ])oints of the excurrent canal walls, still another method
which, as I believe, we shall have to distinguish from the first
one. And this, because it is apparently bound to a more or less
fixed place:

hl sponges ,jfed" on carmine one repeafedly meets with one
large accumulation of this^ matter near each flagellated chamber,
and again in an apparently nndifferentiated plasmic substance, in
the tcall of the excurrent canal (Fig. 73). While, ?wh\ on the one
side new carmine grains are constantly added to the large heap
by the flowing p)lasmic lager, situated at the incurrent-canal-side
of the chamber (p. lol, 1-^6'), one sees on the other side now and
then a big conglomerate being ejected from the heap info the ex-
current canal; both of which is represented in Fig. 73 (drawn
from lifc). I observed this, of course, again in my living tissue
preparations.

Of course it cannot be said, if this accumulation of carmine —

167

wïiich, apparently^ has heen deposited gradualhj lij the foiving
plasmic layer^ so in small quantities at the time — is exclusively
formed hy fine carmine grains^ captured by the chocmocytes and
then p)assed on to tJiis layer^ or hy coarser particles^ which remaiyied
sticking ivhen entering the prosopyles and then have heen carried
off hy this plasmic layer {p. 156). Prohably hoth is the case.

That in this way particles, which block up the prosopyles and
are of no food value, are removed as soon as possible from the
canal systcm, is very well conceivable and of much importance
to the sponge. So here we get to know a very powerful system
of cleansing the sponge: coarse particles^ which, having passed the
ostia, remain sticking in the prosopyles and threaten to hlock them
up permanently^ are taken up hy the plasmic layer and are carried
off to a point in the tissue somewhere in the neighhourhood, froni
tvhere they are soon ejected into the excurrent canals, to be removed
ivith the ivater current {Fig. 73).

On the other hand it is hardly to be accepted that coarse
particles from the water, whicli might be of use as food, should
be ejected in this way without auy reason. But then one has to
suppose, that the sponge knows to decide whether a captured
partiele contains nutrition or not, in the short distance between
taking up in the plasmic layer and delivery at the deposit of
feces. This seems very unlikely to .me; the more so, because
above we have stated several times (p. 146 — 148, 157 — 158) that
carmine, most certainly, i« carried into the sponge tissue and is
moved on for digestion to the amoebocytes with green symbiotic
algae, to be expelled only later on (p. 161 — 164). So it proves,
that only the amoebocytes with symbiotic algae — which are
performing the function of digestion (p. 157) — decide about
food or no food with regard to the particles captured. Consequently,
one may consider it as excluded that the same could also happen
already near the flagellated chamber.

The explanation of the phenomenon, that on the one hand the
sponge carries the carmine even into its amoebocytes, while on
the other hand it disposes of a very rapid method of getting rid
of it immediately, seems to me the following : "VVith a relatively

168

small niimber of particles in suspension in the surroundino- water
the sponge will carry all particles captured into its amoebocytes
with symbiotic algae, so into its digestive organs (Fig. 71); but,
when the particles in suspension are very numerous, it will also
carry a number of them within its amoebocytes, but soon „satisfied"
will leave oflF, to simply eject them, directly after capturing (in or
near the flagellated chamber), along the shortest way at the •
excurrent side of the chamber, of no consideration wh ether the
particles are food or not (Fig. 73).

We noiv can make the foUomnf/ diagram of the coiirse of the
(food-) iKirticles captured hy a fresh-water sponge (imagine the often
mentioned „intercellular plasmic groundsubstance" (chapt. F) in
the places of the arrows). The pages of the text, in which the
process was treated, and the figures referring to it are put in
parenthesis. So we begin with the capturing in the choanocytes
and the capturing in the plasmic layer at the outside of the
flagellated chamber :

capt. plasm. Ijiyer o. flag. cliamb.

(Fig. 72— 75j
1 fp. 150-54, 156, 174)

Cfipt. choailOC. (p. 143—46, 156)
(Fig. 63, 65—68)

amoeboc. w. symi). alg. (p. 146—8; 156—8).

digestiou (Fig. 69-71) plasm. siibst. o. exc. can. wallj

near flagell. chambers
defecation

(p. 166—68; 170)
(Fig. 73)

plasm. subst. o. exc. can. walls
defecation, exeretion

(p. 161—66; 169—70)
(Fig. 76, 77)

I now want to point out some more accidental peculiarities :
hK Just remember that we could stade a few times (p. 162—
165) that vacuoles together with feces also ejected unicellular,
green algae, even green symbiotic algae. I want to mention this
emphatically witli a view to what I said, in the part about
the chlorophyll of the fresh-water sponges, regarding a possible

169

export of symbiotic algae (p. 52) and a contest against infeoting
algae by ejecting them (p. 115). Especially the question about the
export is important. I do not venture to decide whether it can be
large or not; in both cases here it concerned a green sponge, so
a sponge that came into consideration for possessing an excess
of green symbiotic algae (p. 70 — 72).

2i<i. Sometimes it appears in a living sponge preparation, which
has first been in carmine and afterwards in pure water, that at
last there is still some carmine present in large conglomerates in
amoebocytes with numerous symbiotic algae, and such, in the rim
of the little sponge. This makes us suppose that, besides the
above mentioned defecation inside the sponge at its inner sur-
face, also defecation could take place at the outer surface, for
instance by the ordinary amoebocytes. I have not observed any
thing more certain, however.

3'<ï. I have never discovered pulsating vacuoles in the choano-
cytes, nor ever anything of defecation by these cells.

étli. Finally a question, as I put also on p. 1 53 : What is
in fact the morphological meaning of that often mentioned ap-
parently undiflferentiated plasmic substance, vs^hich, situated in
the wall of the excurrent canals, proved to perform the defecation.
Up till now I have omitted to enter into this question purposely,
in order to evade unnecessarily complicating the problem of de-
fecation, we wanted to know in the first place.

From the conformity of the results obtained from living- and
from ravel preparations (p. 161 — 164) one would immediately
decide, that the apparently undifferentiated substance consists of
amoeboid cells. Also the following supports this view : Just as I
described on p. 153, that I killed and macerated a living sponge
preparation, which had been in carmine and the contents of car-
mine of which I had stated, I did the same with a preparation,
which, according to microscopic research, was in the stage of
carmine defecation given on p. 163 sub 3. All cells were to be
seen isolated. Carmine now proved present : not or little in choa-
nocytes and amoebocytes with symbiotic algae, but numerous and
mostly in large conglomerates — and sometimes together with

170

detritus within a vacuole — in simple to very irregularly branched
amoeboid cells, which lodged a nucleus but few or no symbiotic
algae and for which, in general, the same description counts,
which I gave on p. 153 for the there isolated amoeboid cells.
So these cells have, in short, the appearance of, what I called
in my living preparations, the apparently undifferentiated plasmic
substance. One also sees the striking conformity with what was
found on p. 161 — 164. Consequently this apparently undifferentiated
plasma, which, all over the wall of the (excurrent) canals proved
to bring about the defecation and excretion, belongs to amoeboid
cells. That this also counts for the plasma, which also performs
the function of defecation but then near an apopyle (p. 166 — 167),
was not yet quite decided by this, but I have been able to prove
it in the same way in another preparation. '

Perhaps one is inclined — just as on p. 154 — to look upon
these amoeboid cells in the canal walls as pinacocytes, But for
the same reason as I mentioned there, I believe to be justified
also here in taking these cells rather as belonging to the paren-
chyma. I will return to this subject afterwards.

Next one could put the questions: 1-^*. If, in fact, there is in
principle any diiference between these two kinds of amoeboid
cells — situated in the living sponge as apparently undifferentiated
plasma in the walls of the excurrent canals, the one however
spread all over, the other only near to the flagellated chambers — ,
both of which bring about the carmine defecation. 2^^. If, in fact,
there exists in principle any difference between these two kinds
of amoeboid cells (those of defecation) and the amoeboid cells,
mentioned on p. 153 — 154, which — situated in the living sponge
also as apparently undifferentiated plasma in the walls of the
incurrent canals — lodge the large grains of carmine (p. 149 —
150). I suppose we shall have to answer these questions nega-
tively ; we shall rather have to consider all these amoeboid cells
as identical, each sort only temporarily performing another function
(cnf. p. 149, Ic; 161 — 163). It would even be quite possible that
a cell, which has first taken a number of carmine grains in an

171

incurrent canal, transports them immediately to an excurrent one,
to eject them. I specially think of the case of Fig. 73 (supposed
that the plasmic layer outside and against the flagclhited chamber
also belongs to an amoeboid cell). Even, with the existing dimen-
sions it would be possible, that one single amoeboid cell extends
as well at the outside (incurrent canal side) of the flagellatod cham-
ber as near the apopyle; this cell, in other words, would be able
(without getting out of its place) to take the carmine from the
incurrent canal and eject it into the excurrent one, by simple
protoplasm current within its own body. A very simple and
rapid process!

F. APPENDIX.

SOME SEPARATE OBSERVATIONS ').

First I want to speak about the often mentioned (p. 17, 146 — 148,
150—154, 156, 163, 166, 168—170) uudifferenüated intercellular
plasmic suhstance {ground-subsfance, mesogloea).

As is generally accepted, the tissue mass, which occurs in the
sponges between the pinacocytic epithelium of outer and inner
surface and the choanocytic layers of the flagellated chambers,
the so called parenchyma, consists of ground-substance with
cells. MiNCHiN (45) says about it: „The skeletogenous stratum
(parenchyma) is developed to a very variable extent in different
sponges. Scarcely recognisable in some, in others it attains great
proportions, making up all but a relatively insignificant portion
of the total bulk of the sponge body. It consists of a gelatinous
ground-substance or mesogloea, which contains cells of various
kinds. The mesogloea is the first portion to appear as a struc-
tureless layer between the dermal and gastral epithelia, and is

1) Heie should have followed a description of a remarkable phenomenon in living
gemmule cells of Spongilia; however, I have meanwhile published this elsewhcre
(VAN Trigt, 57 c).

172

probably a secretion of the former. Cells from the dermal epithe-
lium next migrate into the mesogloea, forming a parenchyma
"which is concerned primarily with the task of furnishing skeletal
structures for the support of the sponge body".

Hoirever, the opinion that the mesogloea should be a y^structureless'''
(undifferentiated) mtercellular plasmic suhstance, seems to be nat
rigMi cd least not for Spongillidae.

In 1870 already Lieberkühn (39) came to this conclusion;
and such in consequence of warming the living Spongillae ; for
it always appared then that this groundsubstance split up into
a number of separate cells (with nucleus). ,,In der homogenen
durchsichtigen Grundsubstanz tritt durchweg eine Zerklüftimg
auf, welche sie in gleichmassige Stücke zertheilt, die je einen
Kern mit Kernkörper besitzen". „Diese Beobachtungen lehren,
dass die contractile Substanz" (groundsubstance) „durch Erwarmung
wieder in dieselben Zeilen zerfallt werden kann, aus welchen
sie ihren Ursprung nahm, und das die durchsichtige contractile
Substanz nichts ausserhalb der Zeilen Existirendes ist, sondern
nur ein Bestandtheil derselben bildet". „Man kann sich über-
zeugen, dass die Zeilen die einzigen Bestandtheile der contrac-
tilen Substanz darstellen und nicht etwa noch eine homogene
Sarkode daneben existirt, wie von einigen Forschern angenommen
wird". Lieberkühn obtained the same result by simply pressing
living Spongillae to pieces.

Also Weltner (67) comes to such a conclusion in 1900:
,,Was nun die Grundsubstanz, in welcher die verschiedenen Zeilen
eingebettet sind, anbetrifft, so möchte ich das Folgende bemerken.
Bei einem in Alcohol conservirten Süsswasserschwamme stellt die
Intercellularsubstanz eine hyaline Masse dar, in der die Zeilen
deutlich hervortreten. Untersucht man aber eine lebende aus-
gewachsene Spongille, so bietet die mittlere Gewebsschicht ein
Avesentlich anderes Aussehen dar. Man sieht allerdings hier und
da deutlich abgegrenzte Zeilen zwischen hyalinen Streifen (die
Grundsubstanz) frei bleiben, daneben bemerkt man Körnerhaufen,
in denen man gelegentlich in Folge ihrer amoeboiden Bewegung
einen Zellkern zu Gesicht bekommt. Der übrige Theil des Ge-

173

webes liisst aber keine Zeilen mehr erkennen, sonder das Ganze
stellt eine mit Körnchen von verschiedener Grosse erfüUte Masse
dar, in der man am lebenden Object weder Zeilen noch Kerne
unterscheiden kann. Man erhiilt an solchen Stellen den Eiudruck,
als ob sammtliche Zeilen mit einander verschmolzen seien, ohne
dass man Zellgrenzen walirzunehmen vermag. Wir haben also
hier an einer Stelle ein Syncytium vor uns, an einer anderen ein
gallertiges Bindegewebe. Um die geschilderten Verhaltnisse zu

demonstriren habe ich in Figur von einer lebenden Epliy-

datia fluviatilis ein Stückchen des Parenchyms abgebildet, welches
sich zwischen zwei Nadeln befand. Es Hessen sich hier mit Deiit-
lichkeit 4 Zeilen erkennen, 2 davon mit einem Inhalt von un-
gleich grossen Körnern" (the amoebocytes with symbiotic algae)
„und 2 andere die mit gleich grossen Körnchen erfüllt sind. Von
einer zwischen den Zeilen liegenden hyalinen Substanz war nichts
zu sehen. An zwei Stellen Hessen sich Flüssigkeitsvacuolen er-
kennen. An der freien Aussenflache war niir in dem dickeren
Theile eine Epithelzelle wahrzunehmen, der übrige Theil, sowie
die grossen Lacunen im Inneren, durch die sich ein dunner Ge-
websbalken hindurchzieht, sind ohne Epithel. Solche epithelfreie
Gewebsbalken sind bei Süsswasserspongien eine ganz gewöhn-
liche Erscheinung, so lange die Balken noch von geringer Dicke
sind; sie bestehen sogar oft nur aus einer einzigen lang ausge-
zogenen Zelle. Ausser den genannten 4 Zeilen Hessen sich in dem
abgebildeten Gewebestück keine weiteren zelligen Elemente er-
kennen, vielmehr bestand die ganze Masse aus einer diekfiüssigen
Substanz, in der zahllose gröbere und feinere Körnchen einge-
lagert waren, wie man sie sonst in den Spongillenzellen findet.
Es ist für mich kein Zweifel, dass eine solche Masse aus zusam-
mengeflossenen Zeilen besteht, welche man, wie das Lieberkühn
zuerst gethan hat, durch Anwendung von Warme sichtbar
machen kann".

With the help of my living preparations I have now been
able to state exactly the same thing as what Lieberkühn and
Weltner found, before I knew anything of the observationa of
both these investigators. So my observations have been made

174

quite independent of the former. I too foimd in living tissue the
amoebocytes with symbiotic algae and the cells with equally
large grains imbedded in an apparently imdifferentiated inter-
cellular plasmic ground-substance (p. 17, 146 — 148, 156, 168,
Fig. 69, 71), in which numbers of enclosiires (eg. oildroplets
and sometimes symbiotic algae) and also vacuoles (p. 163 — 165),
and which, at the side of the canals, was one time lined by
cells (eg. pinacocytes) and not so another time (p. 154). "When
rubbed to pieces as well as when warmed, or af ter killing and
macerating, the whole tissue^ so also that undifferentiated plasmic
subsfmice, proved to ronsist of amoehoid cells with nucleus (see
also p. 153—154, 169—170).

As to the observation, that that plasmic substance (i. e. the
ground-substance of the parenchyma) was not entirely lined with
pinacocytes, I mentioned already on p. 154 that the possibility is
not excluded that pinacocytes were present in fact, but not to
be discovered by their line extension. With regard to the above
described phenomena of ingestion of food in the flowing plasmic
layer outside and against the flagellated chamber (p. 152) and
of defecation by vacuoles in the excurrent canal walls (p. 163 —
166), it seems more likely that, at least there where those pro-
cesses take place, the pinacocytic covering of the canals will be
missing. Por that would certainly advance the rapidity. On the
other hand my observation made during the capturing of coarse
food particles outside and against the flagellated chamber, viz.
that first the partiele remains quiet for about 10 minutes before
being carried off by the flowing plasmic layer (p. 152), might
possibly show that thin pinacocytes, which then must first be
passed by the food partiele, are present.

As we have now seen that all apparently undifferentiated plas-
mic ground-substance consists of amoeboid cells, we may conclude
that the layer of flowing plasm at the outside of the flagellated
chambers (p. 152, 156) is also formed by such cells. And we
may also conclude that the (food-) transport (from the choanocytes
to the amoebocytes with symbiotic algae, for instance) which, as
we saw above (p. 146 — 148, 168), takes place through the so

175

called intercellular ground-substance , is in fact performed by
amoeboid cells.

In connection with what was said on p. 170 we can put tlie
question again, if in fact there is in principle any difFerence
between all those various kinds of amoeboid cells, which —
appearing in the living sponge as undifFerentiated plasmic substance
(p. 168) — on the one side, as we saw, capture coarse (food-)
particles from the water (p. 152, 156, 174) or lodge them (p. 149 —
150, 153 — 154), on the other side perform the function of defe-
cation and excretion (p. 163 — 166, 169 — 170), and in the third
place form the „intercellular" groundsubstance of the parenchyma
(p. 171 — 174). I suppose to have to answer also this question
negatively. They are more likely to be all the same cells, each
kind only temporarily performing another function. See also
p. 170—171.

And at last the question, if these amoeboid cells — which, as
one knows, lodge but few or no symbiotic algae — are perhaps
identical to the amoebocytes with numbers of symbioti-c algae,
again differing from them only by a temporarily other function.
Also this would be possible (cf. p. 149, 162). But I do not
venture to answer this question; I only want to ask. See also
Weltner (68).

II.

One must not confound the often mentioned food-(digestion-)
vacuoles of the amoebocytes with symbiotic algae (p. 94 — 97,
111) and the defecation and excretion vacuoles of the amoeboid
cells without symbiotic algae (p. 162 — 166) with a peculiar
vacuolising of the tissue of the outer, and sometimes also the
inner sponge surface, which gets something of a foamy structure
by it. I mentioned it already on p. 17, and such with regard to
a similar structure in isolated amoebocytes (Fig. 4). I think that
this last kind of vacuoles will properly not belong to the cells,
but are rather parts of the surrounding water, which were tem-
porarily enclosed by the pseudopodia during the amoeboid motion

176

of the cells. Therefore one sliould sharply distinguish them from
the food- and the defecation- and excretion vacuoles, the contents
of which of course belong to the cells themselves. Lieberkühn
(39) already drew attention to this.

III.

We have a very easy criterion to make out whether a fresh-
water sponge, in which there are neither gemmules nor finger-
shaped branches, is a Spongilla lacustris or an Ephydatia fluvia-
tilis, viz. in its smell. Spongillae, namely, have a pungent smell
(pungent for instance as formol); while Ephydatiae entirely lack
it. Several persons have, on my request, stated this difFerence;
but it also proved to me that not everybody is able to notice it.

SUMMARY.

This summary gives the chief resiilts of my research, and the
pages of the text, the tables and illustrations concerning them.
See also van Trigt 57b.

1. The two chief forms of Spongilla lacustris and Ephydatia
fluviatilis are a grass-green and a colourless (creamy-white) one
(p. 15—16, Fig. 1, 2).

2. The sponge owes its green colour to uumerous little green
corpuscles present in its tissues, especially in the amoebocytes
(p. 16 — 17, Fig. 4, 69).

3. These green corpuscles produce O2 (p. 18 — 20, Table 1, 2)
and photosynthesise (oil) in light (p. 20 — 21, Table 3), but not
so in darkness. Consequently — in connection with the points of
similitude already known (p. 17) — we are justified in declaring
that the green colouring-matter of the Spongillidae is identical
with vegetable chlorophyll (p. 21).

177

4. The green chloropliyll corpuscles of the fresh-water sponges
are round or oval, 1.7 — 8.8 /y. in diameter, surrounded by a cell-
wall and consisting of protoplasm and a chloroplast; while perhaps
a nucleus is present, but a pyrenoide is absent. They enclose
oildrops, but carbohydrates were never to be found within them
(p. 21—27, Fig. 5, 40, 41, 6—11).

5. These green chlorophyll corpuscles, isolated from the sponge
tissues, remain normal and aliye for 6 months and even longer,
and multiply (p. 27, Table 4). They also occur free in nature,
in the waters in which the sponges are living, where they also
multiply (p. 27—28).

It proved possible to me to durably transmute colourless Spon-
gillidae into the green form, by infecting them with isolated
green chlorophyll corpuscles (p. 28, Table 7, 8).

So the green chlorophyll corpuscles prove to be organisms, on
the one hand capable of living by themselves without the sponge
body, on the other hand of accommodating themselves to the life
within the sponge tissues, wlien taken from the surrounding water
by the sponge. This result together with that of 4, mentioned
above, justifies the conclusion, that the green chlorophyll corpuscles
are algae, associated to the sponge in „symbiosis" (p. 21 — 24, 29).

6. This green „symbiotic" alga of the Spongillidae multiplies
by simple, vegetative division of the whole mother cell, not by
„freie Zellbildung" (p. 30—33, Fig. 5, 12—34). Thus the alga
does not at all answer the definition of a Chlorella (p. 29 — 30,
34), but — in connection also with its structure (p. 24 — 27) —
that of a Pleurococcus (p. 34).

7. Generally speaking, green Spongillidae grow in light, colour-
less ones in darkness or in twilight (p. 35) ; while green sponges
grow colourless in darkness, and colourless ones grow green in
light (p. 35, Table 8).

8. In the green sponges in light as well as in the colourless
ones in darkness green as well as colourless „symbiotic" algae
occur (p. 35, 46, 48, Table 6).

9. Several of those colourless alg-ae have exactlv the same

structure as the green ones (p. 36, Fig. 35),

12

178

10. The isolated green „symbiotic"' algae of the Spongillidae,
in water, can produce chlorophyll in darkness (p. 37, Table 4 B).
Those green algae also, whether cultivated in light or in dark-
ness in poor or in rich organic feeding media, remain normal
(green, for instance) and alive for months, and multiply ; while
the isolated colourless algae under similar conditions disappear
from the culture and never pass into the green form (p. 38 — 41,
Table 4). It proves, therefore, quite impossible that the green
algae pass into the colourless ones and that the colourless algae
pass into the green ones, by the combined influence of darkness
or light and a certain feeding milieu (p. 41).

11. The green „symbiotic" algae, whether isolated or in the tissues
of the Spongillidae, become colourless exclusively by dying, in order
to gradually pass from colourless algae with clear structure into
the successive stages of „solution", colourless algae with shade
of structure, colourless ones without structure, vague shades of
colourless ones, and to finally disappear (p. 42 — 45, Table 5, Fig.
35—37).

12. Analyses were made of the intrinsic amount of the various
green and colourless stages of the „symbiotic" algae in the tis-
sues of a large number of green Spongillidae from light and of
colourless ones from darkness, and such in tissues in different
stages of development (Table 6). The results are to numerous to
be repeated here; they are mentioned on p. 46 — 48, point 1 — 11.
In short we can say, that a green sponge in light contains an
excess of green living algae and a smaller number of colourless
dead ones; a colourless sponge in darkness, on the contrary, an
èxcess of colourless dead algae and a smaller number of green
living ones (p. 48).

13. The factors, ruling the number of the „symbiotic" algae
in the sponge tussues, were studied separately (per unit of time
and per unit of sponge-volume). These factors are 6 in number:

a. The import (/) of the algae from the surrounding water
into the sponge tissue, a powerful and continually acting
factor in nature and equally active in light as in darkness
(p. 49—51, Table 7). ,

179

b. The export (e) of the algae from the sponge into the sur-
rounding water, an uncertain but probably not important
factor (p. 52, Fig. 76).

c. The reduction (r) of the sponge tissue to a smaller volume,
a factor which in nature only occurs in autumn and then
might cause increase of the concentration of the algae in
the tissue (p. 52 — 53).

d. The growth (r/) of the sponge tissue, which in a long space
of time must strongly lower the concentration of the algae
in the tissue and which is more active in green sponges in
light than in colourless ones in darkness (p. 53).

e. The intensity of multiplication ())tii) of the algae, which in
sponge tissue in equal concentration of the algae is much
larger in light than in darkness, in light in a strong con-
centration larger than in a weak one, but in darkness in
both cases + O (p. 54—56, Table 9, 10).

f. The mortality {mo) of the algae, which in sponge tissue in
equal concentration of the algae is much larger in darkness
than in light, in darkness in a weak concentration some-
what smaller than in a strong one, but in light in both
cases almost just as large (p. 56 — 62, Table 6, 8).

14. By cultivating the sponges under such circumstances, that
the factors of import, export, reduction and growth were al-
most entirely excluded, we could show that the phenomena —
that green sponges grow colourless in darkness and colourless
sponges grow green in light — must be explained as being caused,
under these circumstances, by the combined action of the multi-
plication and the mortality of the „symbiotic" algae (p. 62 — 66,
Table 8). And we were able to prove, by means of the above
mentioned data concerning those two factors, why they must
cause those phenomena (p. 66 — 67).

15. Next we have proved with the help of the above given
data concerning all 6 factors (import, export, reduction, growth,
multiplication and mortality) : I. Why in nature the Spongil-
lidae must contain such an amount of the various green and
colourless stages of the „symbiotic" algae in light and in dark-

18Ó

ness, as we have experimentally stated, in short above sub 12
and in extenso onp. 46 — 48 sub 1 — 11. II. How in nature these
sponges keep up their „colour" (green or colourless), and how
both „colour "-types arise froni each other. For, what happens
eg. to the number of green algae of a sponge under certain cir-
cumstances, in other words how the colour of the sponge is af-
fected, entirely depends upon the value which each of those 6
factors takes under these circumstances in the formula

>

i + r + niu == e -\- g -\- mo

<

the formula, which we have got to know as decisive for the
number of green algae of a sponge (p. 68 — 75).

16. By a comparison of the behaviour of the „symbiotic"
algae wheu cultivated in sponge tissue and isolated in water, we
got to the folio wing conclusion : In darkness the „symbiotic" as-
sociation of sponge and alga offers much less advantage to the
alga than a life free in the water, as in the sponge all algae
are destroyed (p. 77, 83, Table 10). In light, on the contrary,
that „symbiotic" association offers more advantage to the alga
than a life free in the water; that advantage, ho wever, only
consists in the fact, that the sponge protects the alga against
destruction, eg. by enemies (p. 76 — 80, Table 10). The milieu —
the feeding milieu — , on the contrary, is in the sponge not at
all more favourable to the alga than in the water, neither in
light nor in darkness, but about just as favourable or even less
favourable (p. 77, 80—83, Table 9, 10). When further we know
that also in light algae are constantly destroyed in the sponge
— though less than in the water — , we must conclude, that
from the point of view of the use to the alga that association
with the sponge cannot be called at all a symbiosis in the mean-
ing of that of the Lichens (p. 84, 113*— 114).

17. We could establish in 26 points the facts which bear upon
the question about the use of the „symbiotic" association (with
the alga) to the sponge (p. 84 — 95, Table 11 — 15).

181

With the help of these data we got to the following conclu-
sion concerning this questión (p. 111 — 114):

It is either the want of food of the sponge or (and) the „poi-
sonous" influence of harmful products of metabolisni of tlie
sponge (to be considored as a reaction of defence against a fo-
reign intruder), which continually destroys green „symbiotic"
algae in the amoebocytes ; and exactly those algae, the power of
resistance of which is already weak^ned for some or other reason
(p. 102—109). All algae killed in this way come to the benefit
of the nourishment of the sponge ; as this one digests and dis-
solves them entirely either free in the protoplasm of its amoebo-
cytes or in food vacuoles, keeps the products of the decomposi-
tion (p. 96 — 97) and rebuilds its own cell parts with them, for
instance the oildroplets and carbohydrate globules (p. 98 — 102).
These oildroplets and carbohydrate globules in their turn are,
among others, the source of the great quantity of energy, which
the sponge transforms in the flagellar motion of its choanocytes
(p. 100).

For the present no decision can be given about the exact signi-
ficance for the life of the sponge of the 0^, which the living
green algae in light secrete within its tissues (p. 93). It may be,
that this O2 is of much significance ; even so much, that the
katabolic phase of the process of metabolism in a green sponge
in light has quite another course by it — namely gives a rela-
tively much larger quantity of energy to the sponge — than in
the sponge in darkness (p. 98, 103, 109 — 110). Some indications
were found for this possibility.

Direct transfer of products of photosynthesis from the living
green algae into the sponge tissue does, most probably, not take
place at all (p. 96, 87, 92).

When next we ask, what in fact the „symbiotic" relation of
sponge and green alga is, considered from the point of view of
the use to the sponge, we cannot very well answer that questión,
before the problem, mentioned above, about the significance for
the sponge of the O2 secreted by the green alga in the light,
has come to solution:

182

a. If the significance of tliat ü.^ is in fact so important, as
was thoiight possible above, we must conclude — notwith-
standing the fact, that the sponge continually destroys and
digests numbers of algae, and notwithstanding all other
phenomena, which do not seem to go together with a sym-
biosis — that the relation of sponge and green alga, con-
sidered from the point of view of the use to the sponge, is
in fact a symbiosis, though this symbiosis is by no means
so complete as that of the Lichens.
h. If, on the contrary, the significance of the 0^ secreted by
the alga is only of little importance, we can conclude —
whatever may be the real cause of the dying of the algae
in the sponge tissue, whether it be the want of food of the
sponge or (and) the „poisoning" of the algae by products
of metabolism of the sponge — we must conclude that,
practically spoken, that so called symbiotic relation of sponge
and alga is in fact nothing but simply a process of nutrition
of the sponge, or, if you like, a very first transition of a
process of nutrition into a symbiosis. At any rate this always
counts for a sponge in darkness.
For we could state the following:

The sponge continually imports green algae from the sur-
rovmding water into its amoebocytes (p. 50), where those algae
then — it should be explicitly mentioned — are killed and
digested (p. 111) by the sponge only for a part, when circum-
stances are favourable, while the rest of the algae can live on,
photosynthesise and multiply (and will give their O.,, produced
in light, to the sponge tissues (p. 93) — the only argument one
can mention in favour of the conception of symbiosis!). This
favourable case is only realized in sponges growing in light
(p. 70—72), and then not even always (p. 41, 75—76). If, however,
the circumstances are somewhat less favourable — as is the rule
in sponges in darkness (p. 69—70) and as sometimes happens
also in those in light (p. 41, 75—76) — , then all imported algae
(and all that might be present already) are continually and un-
avoidably destroyed and digested by the sponge (p. 111).

183

18. Also soine other viows were given concerning the asso-
ciation of sponge and green alga (p. 114 — 116).

19. Some cases were mentioned, in whicli quite other algae
(than the normal ones) occurred in a great number in the tissues
of Ephydatiae, viz. two filamentous algae and an unicellular one.
The two former proved to destroy the sponge tissue; the lattor,
on the contrary, was finally conquered by the sponge (p. 115 —
118, Fig. 43—52).

B.

20. ïhe current of water through the canalsystem of the fresh-
water sponges is caused by the flagellar motion of the choanocytes
iij the flagellated chanibers. By studying isolated choanocytes as
well as wholly intact flagellated chanibers we could state, that
this motion (in normal condition) takes place in a spiral- or an
undulating-line, namely in a very rapid succession of waves of
small amplitude passing along the flagellum from the base to the
top (p. 124 — 132, Fig. 56r^, 59); by which a current of water
arises straight through the axis of the flagellar spiral and simi-
larly in the direction from base to top, while the water flows
on at the side of the base (p. 126—128, Fig. 56ff). Exhaustion
causes quite different motions of the flagellum, with abnormal
current of water (p. 127—128, 131, Fig. 56/>c^). The whole water-
current within a flagellated chamber is of course the resultant of
the little currents caused by each flagellum separately ; it is rapid and
regular (p. 132—133, Fig. 63). In order that a powerful and steady
current may be maintained by the chamber, and that, therefore,
the water will flow in quickly and exclusively at the prosopyles
and flow out by the apopyle, the structure of the flagellated
chamber must comply with definite requirements ; these require-
meuts were studied (p. 137, 133 — 136).

C.

21. By studying the phenomena of ingestion of food in nor-
mall y living microscopic prepar ations of sponge tissue, I could
state that in fresh- water sponges :

184

The small (food-) particles are captured from the circulating
water within the flagellated chambers, viz. outside-between the
collars or between the bodies of the choanocytes, while thus,
so to say, the water is filtered clear (p. 142 — 146, Fig. 63, 65 —
68). Next these particles are taken up within the choanocytes,
united to conglomerates and ejected again into the „intercellular
plasmic ground-substance" (p. 146 — 148, Fig. 66, 69 — 71), from
whence the amoebocytes with symbiotic algae take them up in
their turn (p. 146—148, Fig. 71).

The coarse (food-) particles are captured from the circulating
water outside and against the flagellated chambers at the side of
the incurrent canal, and such, because they remain sticking in or
against the prosopyles. The thin layer of apparently undifFerent-
iated flowing protoplasm, which covers that side of every flagel-
lated chamber with the exception of the prosopyles (p. 151 —
154, Fig. 72 — 74), then takes up each partiele and carries it off
aside into the tissue, so that the prosopyles again become access-
ible (p. 148—152, 155, Fig. 75).

Finally the question was discussed, whether food can be cap-
tured by the sponge in still more ways (p. 155 — 156).

22. No observations were made which could fortify the theory, that
sponges feed especially on organic substances in solution (p. 138).

D.

23. My principal results regarding the digestion of food have
already been mentioned in the discussion of the symbiotic relation
of sponge and alga (see point 17). I only added some new obser-
vations (p. 157 — 158).

E.

24. By observing the phenomena in my normally living mi-
croscopic preparations, I have come to the conclusion, that in
fresh-water sponges defecation — and very likely excretion
at the same time (p. 166) — -■ takes place on a large scale by
means of vacuoles, which occur along the walls of the excurrent

185

canals in an apparently undifferentiated plasmic substance (p.
160—168, Fig. 76, 77, 73), that in reality consists of amoeboid
cells (p. 169—171).

25. Defecation perhaps also can take place at the outer sur-
face of the sponge (p. 169), but I have never observed choanocytes
performing the function of excretion or defecation (p. 169).

F.

20. The common opinion, that the ground-substance of the
parenchyina, the mesogloea, should be an undifferentiated inter-
cellular plasmic substance, proved to me not right for Spongilli-
dae. The mesogloea entirely consists of amoeboid cells, just as
LiEBERKÜHN and Weltner stated (p. 171 — 175).

Leyden, Zoological Laboratory,
August 1918

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TABLES.

Table 1. The production of gashiihhles (0^'^) hy green Spongillidae
in hright day- or sun-light. Sponges nêwly captured; placed separa-
tely into cylindrical glass vessels — capacity 5 L. (a. h.) or 3 L. (c.) —
füled with water from the conduit, in the open air; sponge-pieces of
equal volume in all series of experiments; an inverted funnel and tube
placed under water over each piece. The sponges in darkness under
a light-tight case. Column A indicates the presence (-f ) or absence ( — )
of gasbubbles within or at the outside of the sponge tissue ; column B
the same for the inside of funnel and tube; column C the same for
all outside the funnel and tube. Tlie sign = indicates the number of
gasbubbles to be unchanged. All series of experiments are mentioned.
As for the discussion, see pag. 18. In c. the green sponge-pieces are
taken from one specimen.

a. Spongillae; in light; vol. lO cM^.

colour of sponge

green

colourless

n" of culture

297

296

date

hour

A,

B.

c.

A.

B.

C.

25. Yll. '15

10 a. m.

»

1 p.ni.

+ +

—

»

6 „

+ +

+ + +

—

+

26. VII.

6 .

:=

=

=

190

h. Spongillae; in light; vol. 3 cM^.

colour of sponge

gi-eeu

colourless

n" of culture

302

303

date

hour

A.

B.

C.

A.

B.

c.

28. VII. '15

11 a. m.

»

1 p.m.

+ +

+-

—

+-

»

4 „

+ +

+-

—

+-

n

7 „

+ +

+ + +

+-

—

+-

+-

29. VIT.

7 „

=

=

=

=:

r=

=

c. Spongillae; vol. 1| cM^.

colour of sponge

green

green

colourless

n" of culture

401

400

402

in light or in darkness

darkness

light

light

date

hour

A.

B.

C.

A.

B.

C.

A.

B.

C.

2. IX. 16

11 a. m.

in «

6 p.m.

—

+-

+-

+
+ +

+ + +

+-

—

+-

+-

Table 2. The production of 0.^ hy the isolated green chïorophyll
corpuscles of the Sjmigillidae in light ; proved by means of the
Engelmann bacteria-method. Ravel preparations of living sponge tissue,
to which some material from a bacterial-culture was added and also
some small airbubbles, under coverglass surrounded with vaseline
(pag. -12, i). Column A indicates after how long a time in light or
in darkness the preparations were observed; column B indicates the
disti-ibution and the intensity of motion of the bacteria tlien stated in
the preparation. The chief experimental series has been mentioned;
in all others the result was the same. As for the discussion, see
pag. 19—20.

1 1

cc ,

(U

Oi i

03

3
cc

ition
motion

-73 3 i2

e ^ 03

O

rou
airbu

tion

'S

a
o

a

o
o.
cc

cc

cc
a;

3
_o

"o

m

iqual distribu
■ather violent

ccumulation
iolent motion

eiy weak m^
where

ery weak mot

o

<u ^

C3 > >

> 1

cc ,

.

OJ

— -2 i

S

3

sla

?»

co

cc

o

o

'♦->

Q '^

'S

bc

a
o

cc

cc

cc

3

m

!qual dis tri butio:
•ather violont mi

mulation i
nt motion (aii

weak motio
here

fl
.2

H-s
O

s

03

o;

_o
"o

3 ^ !^ &

ë .2 s:

o;

o

w ï-i

03 P- ?-

?■

■^

>4-< *4 _

^£

'S

O "" 'S

-<

-S

^ cc

-Hl-* r- j,

1. O ^

6 .SP

03

S -a ^

>,' Ö

s
s

^ a 13

0) .rt

"^ 03

.^ -^

o i

S

,

03

03

round
•bubbl
m els

>

S

>

03

r*

03

O)
3
c«
cc

fl
_o

a o

o

'S

o

O

'S

>
O

O

'S

P»
O

■'■+J

o a

•= .2

a

'S

rH

'S

fl

'S

bD

fl

O

o,

cc

pa

distributi
■ violent i

accumulation |
violent motion (a

very weak mot
where

.2

'■*3
o

a

03
03

fl
.2

o

a

-t-3

_o
'■+2
o

a

c3
03

,-H

_o
+3
o

a

.2

o

a

03

fl
_o
'■+3

o

a

<1>
bb

equal
rather

03

a

Oj

'S

fl

3

s

a

03

3

'p-

cc ,

03

.

03

3

V2

a

"0 3 "^
a ^ 3

3 :3

O

o

CC

tion
mot

ro
'airb

ition

'S

ö

'S

a
o

■ m

rO a

fl g a

'-5
o

s

C3
03

"i-

r^

S

p»

fl
o

-

Oh
CC

a

03

bb

^ o

cc •-.

^ r

er 03

' 03 -„

accumulati(
violent mot

very weak
where

o

a

+i
fl

03
3

co ,

03

u

CL;

rH

T3 3 "^

>

03

3
cc

O

fl J2 OJ
3 3

O

f*
O

cc

ai

p X a

'S

-; ,

'•+->

.2 a

^ .5 o

c3 "43

fl

'S

03

.«■j

_o

bC

a
o

Oh

CQ

al distribu
ler violent

a § S
.2 -^ ^

"-J3
o

a

fl

'■+J
o

CC

a

03
03

mulat
mt mo

weal
here

Ti

03

a

a

03

bO

equ
ratl

accu
viole

very
w

>

O

'?

"03

c*- fl
o •-' cc

rJ CC

-^ -c

. 03

. cc
-fl cc

03

rfl -U

cc
• en

^ 03

J3 HJ

cc

ja +^

1

<

immediat

"3

H-t a 2
1 5 fl

o ^

aft. 1 0. a
iu darkn

rH|ïi a

;, S

if fl

Oj ""

after ?
in darkn

after ?
in ligh

after ?
ia darkn

after ?
in ligh

192

Table 3. The production of oildrops hy the isolated green chloro-
phyll corpvscles of the Sponriillidae in light. Ravel preparations of
living sponge tissue (pag. 12, i). Column A indicates wether the
chlorophyll corpuscles were in liglit (1.) or in darkness (d.) during the
pefiod preceding the examination; column B indicates the number
stated of green chlorophyll corpuscles containing an oildrop per 100
green corpuscles. Some less exact experimental series are left out. As
for the discussion, see pag. 20.

a

. (Spon

gilla)

b.

Spongilla

n» of
culture

161

162

163

164

165

n" of
culture

208

209

210

211

date

A.

B.

A.

B.

A.

B.

A.

B.

A.

B.

date

A. B.

A.

B.

A.

B.

A.

B.

25. II. '15

1.

68

1.

71

d.

47

d.

71

d.

41

16. III. '15

d.

38

d.

18

d.

42

d.

16

1. III.

M

77

n

68

n

38

1.

70

1.

42

9. IV.

1.

85

1.

87

n

38

n

16. III.

»

93

n

100

n

40

»

93

n

100

„ih. later

1.

70

1.

68

9. IV.

1.

90

11 V.

n

90

»

97

d.

88

d.

92

c.

(Sp

ong

illa)

n" of
culture

396 a

396 b

396 c

396 d'

o

m
bc

03

396 e

396 f

396 g

396 h

C3

date

A.

B.

A.

B.

A.

B.

A.

B.

>
o3

A.

B.

A.

B.

A.

B.

A.

B.

>

ei

16. VIII. '16

d.

42

d.

30

d.

34

d.

60

42

d.

d.

d.

d.

18. VIII.

1.

82

1.

74

1.

82

1.

80

79

■n

44

»

40

»

22

n

36

35

20. VIII.

n

96

n

92

n

94

1)

94

94

1.

78

1.

74

1.

86

1.

76

78

22. VIII.

»

88

»

78

n

92

»

90

87

Table 4. Cultures of iJie isolated. green and colourless chlorophyll
corpuscles of the Spongillidae ni various feeding media in light and
in darkness; their cornposltion examined hy means of microscopic
preparations (pag. 12, i). The manner in which these cultures were
obtained and kept, as well as the composition of the media, is
mentioned on pag. 9 — 12.

193

In the tables A — D is indicated: a. The n'' of each culture, h. The
species (sp. = Spongilla ; ep. = Ephydatia) the culture lias been taken
from. c. The date of the beginning. d. The nature of the culture-
medium (last column), e. The composition of the culture from the
first day till as long as it was kept; so column 1 indicates bv
-}-, O, or — wether in the culture the green substance (n.b. exclu-
sively that of the green chlorophyll corpuscles, not that of otlier algae
wliich might the present) is increased, i^emained the same or decrea-
sed; column 2 wether in the culture occurs a strong (-[-), a small ( — )
or no (n) ') infection of algae (a.), bacteria (b.), diatoms (d.) or of
mould (m.); column 3 indicates the number of the gi'een chloropbyll
corpuscles present in the whole (microscopic) preparation ; column 4
the number of tlie green stages of division of tliose corpuscles; column
5 the number of the ,,colourless chlorojdiyll corpuscles witli struc-
ture" (p. 42); column 6 the number of the ,,colourless chlorophyll
corpuscles witliout structure" („vague shades" excluded) — again
always the number present in the whole microscopic preparation,
consequently, present in an almost equal volume of each culture.
As for the mode of stating these numbers as well as for the meaning
of the symbols I — XII, see pag. 13 — 15. All data concerning one
culture are united in one horizontal line. Next indicates: an asterisk
to a n" (eg. 69*) that the culture orginated in a colourless sponge,
a zero to a n" (eg. 84°) the culture originated in a green one; in
all other cases the cultures of green corpuscles were taken from green
sponges, that of colovu'less corpuscles from colourless ones; dr. means
that the cliorophyll corpuscles are degenerate, p. that they have
grown pale; while c. denotes that there occur centra of growth of
green corpuscles.

All cultiires are mentioned. To one series belong the following
numbers (put together in parenthesis) — therefore these may be
compared directly — : (37, 43), (65, 66, 72), (68,69), (80, 81), (84— 87),
(91, 92), (113—120), (124—129), (141—142), (145—148), (188—198),
(199—204), (240—242), (.309-316), (319—321). The cultures n« 72
and 86 were in the inorganic solution I of pag. 10; n" 114,118,125,
128 in tlie inorganic solution II; n" 87, 141, 142, 146—148 in tlie
diluted organic solution III; n" 115, 119, 126, 129 in the concen-
trated organic solution II; n" 188 — 195 and 199 — 204 in the concen-
trated organic solution I; all mentioned on pag. 10 — 11. The feeding me-
dia of the other cultures are indicated in the tables (conf. pag. 10 — 11).

As these culttu-es sliould inform us, if and undei- whicli circiini-

1) mentioned in special cases oiily.

13

194

stances green and colourless chlorophyll corpuscles pass into each
other (pag. 37 — 41) — for we will try to explain in this way, why
green sponges occur in light and colom^less ones in darkness, and why
green sponges grow colourless in darkness and colourless ones grow
green in liglit (pag. 35) — ; and as we can see from Table 8, that
in general a green sponge must be in darkness for at least a nionth
in order to grow alraost colourless — during which period its number
of green corpuscles strongly decreases, that of the colourless ones
strongly increases — and that a colourless sponge must be in light
for at least a month in order to grow somewhat green — during
which period its number of green corpuscles strongly increases and
that of the colourless ones increases a little — ; we should observe
01U' cultures of the corpuscles for more than a month.

From the tables 4 A — D results (see also p. 37 — 44) :
7. The isolated green chlorophyll corpuscles, when cultivated in light
or darkness in all kinds of feeding media, remain normal (green
for instance) and alive for months, and multiply l)y normally
green descendants.

?. The green corpuscles multiply more rapidly in light than in dark-
ness (pag. 55).

3. In general tlie number of isolated colourless chlorophyll corpuscles
in the cultures does not increase, but even decreases under all cir-
cumstances raentioned sub i; the corpuscles disappear from the
culture and never pass into the green form.

4. When the green corpuscles decrease in number, the colourless ones
increase; so the lirst ones probably pass into the latter (wliile these
disappear after some time).

>. Bacteria do not seem to harm the green corpuscles; but mould,
diatoras and algae make them grow colourless (n" 84!) (which
colourless corpuscles disappear).

rr

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3 4 5 j 6

1 1 S 3 4 5 16

1 2 3 '4 5 1.

91 ,

~n -1.

H.Vlll
20. Vlll

27. Vin

6. XI
19.1

Il VII

■

■

V
V

11
vil
11

IV

IV

vil X

Vil! X

vil IX
Il X
V Vlll

vil X

IV
IV
V

VI

I ' V

II .

1 VI

l\ VI

VII.

-i- VII 1 .

IV II IV

VI III V

1- IX V lil .

■ 1 '

. ' . 1 .
. . II

. vn

' i "

11: VI

V

I

IV .

V .

I
l''

VI

VI

I

"

V

III

I

I

IV

II

III

■

. I . I UI

1

■ !■
!l j 'i V

ciiltiiies in w;.tyr

;!;ri;r

I-J-, -i. Il, XI

1
IVIl IV 11 1 X

i ,

.1 1 ,

'i'

TIT

iV II l-\

+

IX

I

I

■|-

r

'

■

V

111

I

I

111

1

I

VI

r

i

V I illl V

iiioi'^na. fi-eó- sol.

uo

«]..

10. 1

11

V Iviii

11 V Vil

■ 1 ■
1

!

II

V

vil

II

1

II

■ 1 ■

•

. 1 •

j

.\.:

cultuies in dildted
ni-an- fft-il. f.il.

120
202
203
2fii

■]'■

op.

^1'

CXI
10.111

*

Vil

II
II
II

X

IV

III

1

II X

VI vin
viiviii

VI Vlll

III VI

• ■

. 1 . 1 .

m IV II] X

11. X II

1? , V vil

1 • - I VI
III. X I 1 Vil

)

'

■

+
m.

I

IV

VI

■

■

+
m.

+
ni.b.

I

I
Vil

IV

'

.

+
b.

VÏI

I

I

.

■ ■ ■

... 1 . 1
1 1

conecnir. urg.it).
fced -o\

i 1

88
IW
197"

•!•■

27. Vlll
10. 111

•

II

X
X

X

111

III
III

vil
lil
111
III

IX
VI
VI
VI

11

1
. 1 .

( 1

n .

VII 1 lil jll

v'll 1 IV V
VII lil IV V

1 1
. ) -

'

.

■ 1 ■

.

■

■

+
+

vïn

VIII
VII

■
III

II
II

Vil

I

IX

I

I
II

I
I
I

■

■'■

. 1 . ■

N"-'i'P'"-'i'l'i'd

:'2i', . : 7. vni

vil

Vil
X
X

IV, V Vlll

IV V Vlll

V VII IX
11 IV MM

U. VI; 11 V III

+! Z V 1 11 ir IV-

t; 11. IX III I 1

■ 1

t

(1 t). IX I I II

■

VII
VI
IX

I i IV-
Il i 11=
III

V lil"

VU"
IV=
VI=

.

.

+!

VI

IX
XI

II
I

III
I

11=
III-
11-

III"
v=
111=
ir

■ ■ 1 ' ' '

:i:|::m:

■ r

ciiliiires lil
oi.nn-entr,

195

Tablk 5. The iransition of ifiolated green cliloropjiyll corpusclcs of Uu;
Spongillidae info llic sticcessive eolourless stages^ brought about under
various ciirumstaiu'f's eithei' iii ciiltiii-ps (conf. Tal)le 4) ()i"'in vaseline pre-
parations (pag. l^, J), and studied )\y stating the ininiber of the various
chlorophyll corpuscles present in a microscopie preparation (pag. 13-14).

In the table is' indicated: a. The n" of each culture orof each [irepa-
ration. h. The species (s. = Spongilla; e. = P^plivdatia) froni \vhich
the corpuscles were taken. r. The date of the examination. (L AVethcr
the corpuscles were kept in light (1.) or in darkness (d.). e. The nuin-
ber of the various corjjuscles stated : sub 1 tliat of the green ones,
sub 2 that of the ,, eolourless ones with clearly rnarked out structure"
(p. 42), sub 3 that of the ,, eolourless ones with shade of structure",
sub 4 that of tlie ,, eolourless ones without structure", and sub 5 that
of the ,,vague shades of eolourless ones" without structure. In the last
column is nientioned,'wether these data concern a culture or a vase-
line preparation and under what special circumstances it was. As for
the meaning of I — XII, see pag. 14; and for the discussion, see pag.
43, II ; p. indicates that tlie green corpuscles have grown pale.

m

li

I.

no

O

CL.

date

or
d.

1

2

3

4

5

37

10. VII

1.

X

culture

17. Yll

Xll

I

I

21. VII

X

X

diatom-iiifect.

31. VIII

XII

I

I

68

s.

19. IX

I.

XII

I

I

vas. prep.

P-

6.x

XII p.

I

I

1

in bright

30.x

II p.

X

X

Xll

dayligbt.

15. XII

VI

X

25.1

I

III

IX

XII

14. IV

I

I

111

XII

3. VI

I

I

I

XII

25. VIII

I

I

1

X

3. XII

I

I

I

IX

20.11

I

I

1

Vlll

84

s.

2.ÏX
21. IX

I.

XII
IX

I

X

I

I

I

culture,
diatorn-

6.x

Vp.

xii

infcction.

28.x

IV

XII

X

10. XI

IV

VII

I

1

11. XII

I

I 1

I

851.

s.

28. V

1.

X

1
V

V

culture, alga ;

1.VII

1

VIlI

IV

Vlll

and diatom-

4. VIII

I

VII

1

VII

infect.

94

s.

9. IX

I.

XII

I

I

prep. 3I' in

1

21. IX

vip.

X

il

damp at 83°.

i
t

26. IX

(lo.str.

destr.

196

n»

m

'o

date

1.
or
d.

1

2

3

4

5

95

s.

11. IX

1.

XII

I

I

I

1

vas. prep.

17. IX

XII p.

I

I

I

in bright

19. IX

VI p.

XII

daylight.

6.x

I

XII

I

I

2. XI

I

XII

I

15. XII

XII

25.1

I

VII

IX

X

14. IV

I

V

[I

IX

3. VI

I

I

I

X

H3

s.

11. XII

1.

XII

I

I

I

culture,

21.1

IX

II

transitory

17. III

VII

XII

VII

alga and

25. V

XII

IX

mouldinfect.

21.11

I

I

I

I

114

s.

21. 1

1.

X

V

I

culture, alga

18. III

IX

V

III

VIII

infection.

25. V

V

V

21.11

I

I

141

e.

24. III

1.

X

I

II

culture, alga

27. V

IV

V

II

X

and diatom

21.11

I

I

I

infect.

146

e.

19.1

d.

II

A

I

VIII

culture,

24. III

II

V

VII

normal.

28. V

II

I

II

149

e.

l.III

1-

XII

I

I

vas. prep.

3. VI

I

X

X

3. XII

I

II

XII

20.11

I

I

XII

188

s.

10. III

1.

X

II

I

VI

culture,

26. III

VIII

VII

large in f.

30. III

I

IV

X

of mould.

15. VII

II

IV

VII

189

s.

10.111

1.

X

III

VI

culture,

30. III

III

V

IX

large inf.

15. VII

I

II

I

VI

of mould.

197

1.

no

'o

a,

UI

date

or
d.

1

2

3

1

4

5

190

S.

10. III

1.

X

1
III

VI

cult., smal-

20. III

X

IV

VII

ler inf. of

30. III

IX

IV

IX

mould,later-

1. VI

I

II

1

II

on larger.

194

S.

10. III

d.

X

I

ll

VI

cult., very

26. III

X

I

I

I

srnall inf. of

31. III

X

I

I

VII

1110 11 ld, later-

10. VII

VII p.

I

I

I

on large.

269

s.

24. VI

1.

X

-\

"^

X

vas. pre]).

6. VII

X

I

V

IX

21. VII

X

I

IV

VIII

2. IX

X

I

V

I

VIII

3. XII

lip.

II

VII

X

VIII

272

s.

24. VI

I.

X

7

T

X

vas. prep.

6. VII

X

I

I

VII

21. VII

X

I

II

VII

2. IX

X

I

I

I

VII

3. XII

Xp.

II

III

VI

V

275

s.

24. VI

d.

X

■<

ï

X

vas. prep.

21. VII

X

I

IV

VII

2. IX

X

I

V

I

VIII

3. XII

Xp.

1

III

V

VII

20.11

Xp.

I

III

III

VIII

277

s.

24. VI

d.

X

A

J

X

vas. prep.

2. IX

X

I

V

I

VIII

3. XII

Xp.

I

III

V

VI

281

s.

24. VI

1.

V

A

r

XI

vas. prep.

2. IX

11

I

I

I

VIII

287

s.

24. VI

d.

V

\

r

XI

vas. prep.

2. IX

II

VII

I

VII

290

s.

9. VII

1.

X

V

VII

IX

culture,

12. VII

X

III

V

VII

nor mal.

17. VII

X

I

I

II

31. VII

XII

IV

I

III

24. VIII

XII

I

I

I

198

o

o-

290
a.

290
b.

290
c.

290
e.

290
f.

290
k.

290
n.

290

291

307
1.

s.

date

7. VIT

31. VII

2. IX

7. VII

31. VII

2. IX

7. VII
31. VII
2. IX

7. vn

2. IX

7. VII
2-. IX

17. VII

2. IX
4. XII

4. VIII

3. IX
5.x

4. XII

20.11

4. VIII

3. IX

5. X

4. XII
20.11

7. VII

9. VII

12. VII

21. VII

21. II

3. TX
5.x
3. XII

20.11

28. VIII

I.

or
d.

X
X
X

X
X
X

X
X
X

X
X

X
X

X

Xp.

I

XII
X

IX p.

. I
I

XII
X

Xp.
Xp.
Xp.

IV
IV
VI
VI

I

XII

1
I
I

IV

II
I

IV

II
II

IV

I
I

IV

I

IV

I
I

I

VII
VII

I
I

I

VII
VII

III
I

V
V

I

II
I

I

lil

1

VI

I
I

VI

I
II

VI
IV

I

VI

I

VI

I

I

I

VII

VII

VII

V

I

VII
VII
VII
IV

VII
VII
IV

III
1

I

VII
VII

II
II

IX
V

I

IX
VI

I

IX

IV

I

IX

I

IX
VI

II

III

X

XI
XII
XII

III

X

XI
VII
VII

X

VIII

VI

V

III

V
XII
XII
XII
XII

VII

VI

V

VIII

VIII

III

vas. prep.

vas. prep.

vas. prep.

vas. prep.

vas. prep.

vas. prep.
in briglit
daylight.

vas. prep.
in sunlight.

vas. prep.
in sunlight.

culture,
normal.

VII
VII

vas. prep.
in sunlight.

199

1.

n"

0)

te

date

or
d.

1

2

3

4

5

308

S.

3. IX

1.

XII

I

I

I

1

vas. prep.

1.

5.x

I

I

III

XII

in sunlight.

3. XII

I

I

VI

I

XII

20.11

I

I

I

IV

VIII

318

S.

7. VIII

I.

X

III

III

VI

vas. pi'ep. 3li

5.x

I

I

I

X

at 83°.

Tarlk 6. The mniihcr of Ihc. rarious giweil end coloiirh^ss clilo-
rapln/ll corpuscles present in <li(]ere)if stafjes of devetopnieiit of tin;
tissue of Uring green and eolourless Spongillidae groiv)i in Jight or
in darkness^ examined microscopically by means of ravel preparations
of the tissues (pag. l'i — 14).

It was of much importance to know tlie intrinsic aiuount of cliloio-
phyll corpuscles in the sponge tissue during its different stages of
development, viz. in its [trime youth — when growing vigorously — ,
in fuU-grown state — growing no more — , and in its stage of rest —
as gemmuhie in winter. Young, growing tissue we ünd 1^' in the sniall
(2 — 5 m.M.) sponge-disks, attached for instance to stones, and being
probably newly gerniinated gemniules; 2'"! in the tops of the branches
of Spongilla (p. 1(3); probably, however, tlie disks will ap})ear younger
than the tops. FuU-grown tissue we generally lind all over tlie sponge
body except in the tops, so for instance at the base of the branches
or in the crust (p. 46). This only concerns Spongilla; as mentioned
(p. iG), Ephydatia does not forin long l^ranches but cushions; so in
this sponge we can not distinguish a certain limited region of growth.
There the growth is more general, but then locally not so vigorous
as it is in the tops of Spongilla.

Consequently, for Spongilla I sliali indicate in the table the amount
of chlorophyll corpuscles in 4 groups, viz. for the tissue of l^*^ sponge-
disks, 2"'! branch-tops, S"""! branch-bases or crusts, 4*'' gemmules. In this
last group one may distinguish again the gemmules in difierent
stages of development; their last stage then joins the group of the
sponge-disks. In this way the circle is accomplished. For Ephydatia
we can not give groups of old and young tissue — as mentioned — ;
of course it could be done for disks and gemmules, but this lias been
left out here.

In the tables is indicated: a. The month of the analysis of each

200

sponge. h. Wetlier the spoiige, at the moment of its analysis, was
brouglit trom its habitat in nature to the aquaria for more (n.) or
less (i.) than 2 weeks ago; in tlie first case we may say, that pro-
bably a good deal of the influence of the import of clilorophyll cor-
puscles (p. 50) on the amount of these corpuscles in the sponge will
have disappeared; but not, however, in the last case. c. The number
of the vai'ious chloropliyll corpuscles present in tlie tissue: in column 1
that of tlie green ones, in col. 2 that of the green stages of division,
in col. ;3 that of the ,,colourless corpuscles with structure" (p. 42), in
col. 4 that of the ,,colourless ones without structure" (,,vague shades"
excluded); always the number })resent in the whole microscopic pre-
paration, present, therefore, in an almost equal volume of each sponge.

The data concerning one sponge piece are given on one horizontal
line. Sub 5 the analyses of different pieces of a same sponge are
indicated by the same letters. All analyses are mentioned. As for the
meaning of I — XII, see pag. 1-4. At last for each tissue-group of the
green and colourless sponges the amount of tlie various chloropliyll
corpuscles, present in all analyzed sponges together, is composed.
This composition simplifies of course the mutual comparison of the
results of the different groups.

As for the discussion, see pag. 46 — 48 and 7(3.

X a

„H, t, ^ X X ^ »

<j « H «

►-.. HH i-.»-H<;<;;:3a

5 2 2 3 >< = S

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;: i j: 1^ ;-i

X X

55 X p: X X

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P —

tissue of bi'anch-bases and of crusts; full-growo.

tie 30 together:

ooi.l. : l.IX + -13. X + 2. XI + 14. XII

col. 2. : 5.1 + 5.11 + 5. III + 3. IV + 3. V + 3. VI + 3. VU

col. 3. : l.I + 5. III + 11. IV + 8.V + 4.VI + I.VII

col. 4. : l.VI + 6. VII + 9. VIII + 5. IX + 8. X

tissue of bianch-tops; vigoi-ousl/ growing.
the 21 together:

col. 1.
col. 2.
col. 3.
col. 4.

5. X + 16. XII

2. 1 + 4. III + 1. IV + 4. V + 5. VI + 4. VII + 1. IX

l.I + 7. III + 10. IV + 2. V + l.VI

•l.III + l.VI + 11. VII + 6. VIII + 2. IX

tissue of very young sponge-disks (2 —
5 m.M. diameter): vigorously gi'owing.

the 9 together:
col. 1. : 2. X + 7. XII

col. 2.
col. 3.
col. 4.

l.ll + 4. IV + 1.V + 3. VI
3.I + 1.II + l.ItH-l.IV + 3.V
1.1 + 1.111 + 2. VI + 5. VII

< < X .^ _;

<^<<<j-s;<!<i<l<;

<!<!<!<!

Sks = SxS-xxx

nontb

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= <S<iS33s;:^a<i<:<5<i<iS=:-=ig

<i;3-<s5-;S;5É-;^---

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5 r ^ ;S 5 S

-5 t: o 3 g »o

ta 13 o n

3 O

3 E

3 O

- =^

tissue of brancli-bases and of erusts: full-grown.

the 20 together:

i-ol. I. :(!. Il + l.III + 2. IV + 5. V + 4. VI + 2. Vil

col. 2. : 15. 1 + 3. II

col. 3. : 2. II + 3. V + 9. VI + 4. VII + 2. VIII

col. 4. ; 2.IX + 4. X + 8.XI + 6. XII

tissue of branch-tops; vigorously growing.

the 15 together:

col.1. : l.III + 1. IV + 2. V + 4. VI + 0. Vil + 1. VIll

cnl.2. : 12. 1 + 2. II + I.IV

col. 3. : l.III + 3. IV + 5. V + 5. VI + I.VII

col. 4. : 2. VIll + 12. IX + l.XII

tissue of very young sponge-disks (2 —
5 m.M. diametei'); vigorously growing.

the 11 together:
col.1. : 4.II+2. 111 + 1. V + 3. VI + I.VII
col. 2. : 9. 1

col. 3. : 1. III + 5. V + 3. VI + 2. Vil
col. 4. : I.VII + 4. VIll + 2. IX

201

Tablk 6 B

•

Spongillae

green ones from darkness

culourless:

ones from light

O

i.

01-

1

2

3

4

^ i.

1 01-

I

2

'A

4

s

n.

2 n.

vil

i.

X

I

IV.

IX

VII

i.

VI

I

V

XI

VII
VII

n

X
IX

I
II

IV
IV

X
IX

tissue of bases
and crusts.

VII
Vil

n
n

VI
VII

I

I

V

IV

X
IX

tissue of bases
and crusts.

VII

))

X

I

V

X

VII

n

VII

II

IV

IX

VII

n

VIII

II

III

VI 11

VII

n

VI

I

IV

IX

VII

n

VIII

I

V

VIII

VII

n

V

I

IV

IX

Taüm.

6C

Ephydatiae.

green ones

colourless ones

^

i.

i.

a
o

or

4

2

3

4

0

or

1

2

3

4

s

n.

r^

n.

II

i.

IX

V

IV

IX

II

i.

III

I

VI

X

II

n

X

VI

III

VIII

t—t

II

ri

V

I

VI

IX

>

II

n

X

VII

III

VIII

H- 1

II

n

IV

I

VI

X

II

n

X

VI

III

VII

M S +

XI

n

V

I

VII

IX

+

II

y^

X

VI

IV

VIII

lÓ P> ^

XI

))

VI

IV

VI

VII

>

II

n

X

VI

III

VII

+ ^^ '^•

XI

»

11

I

VII

IX

+ ^

Xil

n.

XII

V

1

•

II

■n

III

11

VI

IX

co

t +

X

XII

II

i.

XII
VIII

V
VI

1
III

VII

1 C-^ O

II
II

II
II

I
I

V
VI

VIII
VIII

II

II

II

IX

XII

X

VI
VII
VJI

VI

V

V

VIII
VII
VIII

+ ^ ^i +

X + + s

■": -^ >

^ s K •

'^ S 00

11
II

VII

51

■n

II
I
I

I
I
I

VII
VI
VI

X

IX

IX

• •

= :• - +

II

IX

VII

V

VIII

ë

VII

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202

Table 7. The ca-plut'c of f/rccii rhlovophyll corpuscles hy colour-
lesn Sj>ongillae front n diluted simpension (in water) of ^uch corpuscles
i^olated ft'oin a green sponge.

Some equal cylindrical glass vessels were fiUed with 3 L. of water
from the conduit; then a same quantity of the material, pressed out
froin a green Spongilla, was added to each vessel of one series; so
all vessels looked equally grayish. This suspension always proved to
contain green chlorophyll corpuscles only, no other algae. Next an
equally large piece of colourless Spongilla was placed in each vessel
of the series, except in one, and all vessels exposed to light or kept
in darkness. Sometimes also an equally large piece of colourless Spon-
gilla was put into a vessel füled with water froni the conduit only,
and exposed to the same conditions.

In the tables is indicated: a. The degree of troubling of tlie culture
suspension (-|-4~ + -|- = "^'^U niuch troubled; ü = clear). b. The
colour of the sponge. c. The presence (-f-) or absence (0) of oscular-
tubes. These data are given tbr several days. The chief series have
been nientioned. As for the discussion, see pag. 28, 49; for the con-
tinuation of the experiments, see Table 8.

Table 7 A.

in liglit; volume sponge 10 cIVP; 9 — VI — '15.

n"

244

245

246

247

248

251

contents of

vessel

suspens.

+
sponge

suspens.

+
sponge

suspens.

+
sponge

suspens.

+
sponge

suspens.

+
sponge

suspens.

degr. of troub.

+ + + +

+ + + +

+ + + +

+ + + +

+ + + +

+ + + +

^st

col. of spong,
osc. tub.

colourless

colourless

colourless

colourless

colourless

day

degr. of ti'oub.

+ + + +

+ + +

+

+ + +

0

+ + + +

col. of spong.

soinewhat

greenish

the gi'eater

greenish

entirely

2'1

greenish-

part light-
green

light-green

day

osc. tub.

+

0

+ + +

0

.+ + + +

degr. of troub.

+ + + +

+ + +

0

+ + +

0

+ + + +

col. of spong.

somewhat

gieenish

the greater

greenish

entirely

Si
day

greenish

part light-
green

light-green

osc. tub.

0

0

+ + +

0

+ + +

Table 7B.

in light; \

203

olume sponge 7 cM',

11— VI-

'15.

n«

253

254

255

256

257

258

259

contents of
vessel

sus])ens.

suspens.

+
sponge

suspens.

+
sponge

suspens.

+
sponge

suspens.

+
sponge

suspens.

+
sponge

conduit-
water

+
sponge

degr. of troub.

col. of spong.

osc. tub.

+ + + +

+ + + +
colourless

+ + + +
colourless

+ + + +
colourless

+ + + +
colourless

4- + + +

colourless

0
colourless

day

degr. of troub.
cöl. of spong.

osc. tub.

+ + + +

+ +

2/5 Hght-

green

0

+ +

V. ligbt-

green

0

+ + +

somewhat

green ish

0

+
3/5 light-

green

+ +

+ +
V2 liglit-
green
ü

0
colourless

+ +

2'!

day

degr. of troub.
col. of spong.

osc. tub.

+ + + +

+

V2 light-

green

0

+
3/4 light-

green
0

+ +

'/2 light-

green

0

0

'U light-

green

0

+

V2 light-

green

0

0
colourless

+

4th
day

T.\BLE 7 C. in darkness; volume sponge 3 cM'; 24 — VJII — '15.

no

325

326

327

328

contents of
vessel

suspens.

suspens.

+
sponge

suspens.

+
sponge

conduit-water

+
sponge

degr. of troub.

col. of spong.

osc. tub.

+ + + +

+ + + +
colourless

+ + 4-

+ + + +
colourless

+

0
colourless

Ist

day

degr. of troub.

col. of spong.

osc. tub.

+ + + +

+ +
Vi liglit-green

+ +

-f
Vi light-green

+ 4- +

0

colourless

4-

2'!

day

degr. of troub.

col. of spong.

osc. tub.

+ + + +

0
Vi light-green

+ + + +

4-
Vi light-green

4- + +

0
colourless

41 h

day

204

Table 8. (kdturea of green and eoloiirless Spongillidae in ligltt or
in darknest^ in aquaria filled ivitJi floiving water from the conduit ;
white tlie colour of the sponges and the nuniher of the various green
and, colourless cldoroj^hyll corpuscles in the tissues changes or remains
constant.

Generally of each sponge some pieces were cultivated in light and
some otlier ones under equal circunistances in darkness; sucli pieces
of one sponge are indicated in the tables witli one n", adding l. or d.,
event. I and II, to it. These cultures, of course, may be compared
directly. The colour, and generally also tlie number of the various
chlorophyll corpuscles in the tissues of eacli sponge (- piece) was exactly
examined (pag. 13 — 15) at the beginning as well as at the end of the
experiment. Mostly the material of the branch-tops was well discerned
from that of the bi'anch-bases (see Table 6 A).

The cultures took place, as mentioned, in aquaria with flowing
water from the conduit or sometimes in glass vessels with 3 L. of the
same (hut not flowing) water. As for the arrangement, see pag, 8 — 9,
The cultures were kept till tlie sponges began to die or to reduce
their tissue ; Spongillae usually after about 1 month, Ephydatiae after
about 2 months. In this way the factors of import, (export), reduction
and growth (p, 49 — 53) were excluded as much as possible in these
experiments ; while as only active factors remained multiplication and
mortality (pag. 54 — 62),

That import was excluded foUows from the fact that the sponges
were Cultivated in water from the conduit. The export is, as stated
above, an uncertain but probably not important factor, The reduction,
as mentioned, was excluded by putting a stop to the experiments, as
soon as it appeared; while, moreover, a continual vigorous circulation
of fresh water through the aquaria tried to limit its tronbling con-
secjuences as much as possiJjle (p. 53). Had these measures been not
entirely sufficiënt (which cannot be decided), one may consider, how-
ever, safely that the reduction will have eqiially influenced all expe-
riments of one series. The factor of growth, of course, can never be
entirely excluded; but in these experiments it was generally but very
weak only (p. 53).

In the table is indicated: a. The n" of each experiment, h. The
species of the sponge piece (s. = Spongilla; e, = Ephydatia). c, Whe-
ther the piece was cultivated in an aquarium (a.) or in a glass vessel
(v,), d. The date of the examination. e. Whether the examined mate-
rial was taken from a branch-t()|) (t.) or from a branch-base (b.).
/'. Wheter the sponge, at the moment of examination, was in good
condition (g.) — showing no or but few reduction — , or that more

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rednction (r.), or some dyin^ (-j-) coiild l^e ol)serve(l. r/. AVliolliei- tlie
sponge had grown very weakly ( — ), rathei' well (-{-) ov vigorously
(-[--[-). //. The colour of tlie sponge; for which I shall make use of
the following expressions, indicating the green colour witli decreasing
intensity: dark green > green > light-green > yellow-green > liglit
yellow-green > greenish > colourless. /. The number of tlie various
chlorophyll corpuscles present in the tissues: sub 1 that of the green
ones, sub 2 tliat of the ,, colourless ones with structure" (p. 42),
sub 3 tliat of the ,, colourless ones without structure" (,,vague shades"
excluded); always the number present in the whole microscopic pre-
paration, so in an almost equal volume of each sponge. As for the
meaning of I — XII, see pag. 14, j. The type to which the sponge
proved to belong during the experiment; in type I the green colour,
therefore also the number of green chlorophyll corpuscles, increases;
in type III the green colour and the number of green corpuscles
decrease; in type II the green colour remains constant as well as
the number of green corpuscles, or the green colour or the number of
green corpuscles changes a little by increase or decrease; in the last case
but one we may speak of a type IF; in the last one of a type IP".

All experiments are mentioned; those belonging to one series are
placed together in one space. As for tlie discussion, see pag. 58 — 66.

In this table has also been registered the behaviour of some colour-
less sponges, which had first been for some time in a suspension of
green chlorophyll corpuscles, which, therefore, had been purposely
infected with those corpuscles (see Table 7); viz. n" 246, 248, 254— 256
etc. For the discussion of these results, see p. 28, 50.

206

Tabi.e 9. Tlie intenslly of nndtiplication of the green chloropJiyll
corpuscies of S2Jongilla in ligïit, ivhen cultivated in sponge-tissue ar
in water r)i a iveak or in a strong concentration of tlte corpuscles.

Of a green Spongilla a piece was cultivated in an aquarium (p. 8 — 9),
while two cultures of green chlorophyll corpuscles in water were
made of the remaining parts (p. 9), one containing the corpluscles
in a weak concentration tlie other in a strong one. The sponge and
the cultures were kept at about the same tempei\ature. In all of them
the number of the stages of division per 100 green corpuscles was
daily examined ■ — sometimes even several times a day — . A darker
green rim was soon formed in tlie cultures to the membrane on the
bottom (p. 40) — ■ the usual way in which the multiplication of the
material is lirst recognized. Of course the chlorophyll corpuscles were
in a stronger concentration in this rim than somewhere else in the
membrane.

In tlie tables is indicated : a. The date and the hour of the exami-
nation. h. The then stated number of tlie stages of division per 100
green corpuscles in tlie green sponge as well as in the cultures in
water, in the membrane and in the rim, in strong and in weak
concentration of the corpuscles ( — means no rim ; -|- rim present).

One day the concentration of the green corpuscles in the sponge
and in the cultures was closely examined and compared. As for the
method used, see p. 81. We shall call this concentration in a dark
green sponge or in a dark green membrane: strong (s.); that in a
yellow-green to light-green sponge or membrane: moderate (m.); and
that in a greenish sponge or membrane : weak (w.).

From the tables results: 1 Periodicity in the multiplication does
not occur (p. 54). 9 The weaker the concentration of the corpuscles
present in a culture the higher is their intensity of multiplication
(p. 55). 3 In strong concentration the intensity of multiplication in
water and in sponge tissue are equal (p. 82). 4 The culture may be
destroyed quickly when infected by protozoa (j). 79).

207

Table 9 A. NO 373.

(hitc

liiiiir

water from cond

uit

rcmarlis.

green
sponge ^

rong conc.

weak

conc.

1'

ini

memb,

rim

memb.

24. VI

0

2G.

2. ]). 111.

4

0

,

0

27.

2. „

4

0

,

0

28.

4. „

3

0

2

29.

11. a. ni.

3

0

2

30.

,

,

,

,

,

1. Vil

11. „

3

0

+
8.5

6.5

~

2.

12. m.

5

0

16

,

3.

0. p. m.

9

2

6.5

,

■

4.

,

,

,

,

,

5.

5. 1,

2

8.5

15

20

6.

2. „

4 (

f

6.5

13

15

7.

10. a. m.

2

9

16

35

8.

II. „

2 i

8.5

16.5

31

11

6. p. ni.

.

.

.

32

9.

10. a. m.

1 (

5

22

30

lü.

10. „

1 ::

12.5

29

32

11.

2. |). 111.

4 t

).5

16

24

31

12.

G. „

0 1

13

5.5

39

13.

0. „

,

,

,

39

14.

0. 1,

2 i

6.5

0

30

15.

12. n.

,

,

,

39

n

4. a. ni.

,

,

33

■n

e. „

.

.

45

V

8, „

.

.

.

30

16.

i. p. m.

2 (

)

14.5

16

29

17.

0. 1,

. ,

,

,

39

23.

11. a. m.

J

28

25

30

-^- concentr.

20.

,

s.

3.

m.

rn.+

w.

30.

10. a. m.

1

20

13

29

2 -

5.3

13

17

33

average since
6. VII

208

Table 9 B. NO 389.

date

hour

green
sponge

water fr

oin lak

e

remarks.

strong conc.

weak

conc.

riiii

Tnemb.

rim

memb.

20. VII

1

_

2

30.

il. a. ni.

1

1

—

0

31.

.

.

,

1. VIII

10. „

0

0

6.5

10.5

2.

10. „

0

1

2

7.5

3.

10. „

1

1

7.5

18

4.

9. „

3

0

12.5

19

5.

9. „

1

1

'20

18

6.

,

,

.

,

,

7.

3. p. m.

2

1

4

12.5

-<- coucentr.

1)

,

s.

m.+

in.

w.

8.

,

.

,

,

,

9.

7. p. m.

0

0

—

10.5*)

*) infect. of

'10.

12. n.

0

0

17

protoz., niembr.

)i

4. a. m.

0

0

10

disappring.

»

8. „

0

1

14

,)

12. m.

0

0

11.5

l-I.

9. )). m.

2

1

4

•18.

10. a. m.

1

7.5

5+)

-}-) membr. +

disappred.

0.8

1

9

12

average since
1. VIII

Table 10. The i7ttensity of multipltcati(yn of the green clüowphyll
corpiiHclc^ of ihe SpongüUdae and the ioitü inerease or decrease of tlie
ii'lioJc nvnihcr of green eorpicscles^ lohen culiivated in sponge-thsue
or in water ^ in Jiglit or in darkness.

Generally of eacli sponge a piece was cnltivated in an aquarium in light
and anotlier one under equal circumstances in darkness (p. 8); such
pieces of one sponge are indieated in the tables with the same n".
All tliese sponges have been mentioned already in Table 8 on account
of the changing of theii' colour and tiieir aniount of various chloro-
phyll corpiiscles. As stated there, the factors of import, (export), reduc-

-^

10 10 co 10 10

-_0 lO 10 10 w
00 ^ o 4s> co

ê ÏD ï^ co co co 10
X <! o *- to

Q, o.

p- ■

co C*3 to

www

-

g g ^ ë '^

.fï. co to -^ C

1 1

3651

365 II

366 1
.360 11

*307
308
369
370
371
372
'374
375
370
377, 379 1., 378, .379 d.

^ = 11

co to W to

5 ü» *^ to

~«

ii

S

"=

,,,,,. *.. PV^V'' gJ.3J«J=-»-»>«>-> ^.>.,. V

3

^'+3 ï«3 ^EnjSS^aa |Sa «

3^3

, . ■,

a a 3 2

a' ^ 3 a 3 a a »

a ^ a a «

M>>>H

■/••

concentr.
at beginniug

5. III
21. IV
19. VI

28. VII

aaaaaaaaaaaaa ^

aa«a33333a33aa <J

3 3 X

" =• ><

<;

^

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a , , . a i

^

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a)OOb0.^o.*o<j.^<iM- o

■ ^-JOCÓ* OOOIOO-JOIO —

Oi ^ to

w *. ^

0 0 to

to <I

• ■ 0 0 0»

't-

— r

Ö

?» i 3 '• !"=■ 3» !»» 3» ^

■aa fnS- «^«j3=» 3^^ «

a a 3

' ' 'T

. . . . ,.,

. . a a w

.,«.,;»

3

■^

35

ra

+ ++ + + + + ^ "!" +

+ oo+ oo++;|;= 1 1 ?T

■ +??+• ??+ ++???

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ooo

+ + + + + 0° +

^ ® 0 0 0

?+++++

1

W

S- • • SSggSggg- S3SS8- • • Sgg- -• ■ --

ggê

^H5s

ggg

1 ra »

00 to eo O *i

S---3^,,^,,^.,.,i---,,4-!'--'?-

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00+55

°+ 1

o 4_ o o
+ T^ + +

111^

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=111 ??'V + -^l°'r- lT+ 1 ■ • • ?°T| M 1 M

<1 0 os ÏD

<1 -.1 *-

gsg

0 m 00

*^

1

3 3 > ^

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• =■ ^

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to

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ra

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1 =Ti 7?i 1 1 1 ??

o' ' 1 lo'ooi loo' '

, 1 1 1 1 =1 1 1 1 1 + i 1 1

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??o 1 M M

00. II

.... 1 i

1
1

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TT

a

— ^J

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— 1 « — —

CO 0 09

»'8|

=.,=«<

a 3 ja

» .» 3 ?■•

^ ^ ^

==■ 5 "

"^ g =:=■

w 1 3
1'

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o o o o (-.

+ + + + •=*

Tl 1

????

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-0 -j

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tn "O

1» 1

3 - a

- -

a a |a

1 1 0

w

3

i333jaa3a3a33a=.J433c<a3.aaj3aaia33a33a-i

+ + +

3333333 = 3^=,^:.:. ;;

' " ■?

3 3 ^

3 a 3 ^

3 a 3 a ^

, , . , . .^

■7

y -.^

= 3 5 3 5 S 5 3 » _ 5. .3 5- s ? = S 2

■A 2 j ^ y^ ~fK n S ri U ^ 2. £ 1= =

■= ? «■ ^

Kil

tllï

8 2 =

1

co

3

after 0 weeks' culturo;
in sponge at first increiiso
of conceiitr. till s.

ra

12II

— -■ E E

aftcr 3 weeks' culture;
in the sponges n" 29.'1 —
295, 298-299 in dark-
ness stages of division
are wholly absent.

P

?

10

t

ra

P

;2
2
co

ra

c
ra

?

ra

c
ra

o

n

55-

e

209

tion and grnwth were excluded as mucli as possible in these expe-
rinients. At the same time also cultures of green chlorophyll cor-
pust'les isolated from tlie same or from other sponges (p, 9) were
made iu water from the lake or (and) in that from tiie conduit. in
light (ir iu dai'kness. Also these cidUires were placed (in l)ottles) in
the aquaria; consequently, all experiments of one series were exposed
to the same temperature. If the cultures (in bottles) arose from the
same sponge, which was also used for the sponge-experiment, they
have no special n" in the table; but they have, when arising from
another sponge (except in n" 41ü — 436). P'or each sponge piece and
for each culture the intensity of multiplication, the concentratiou and
the total increase or decrease in number of the green corpuscles
was examined after some weeks.

In the table is indicated: a. The n" of the experiment, h. The
cbncentration of the green coipuscles in the sponge tissue at the
beginning of the experiment; that in the cultures in water was then
always weak (w. or w. +}, only in n" 3ü9 — 316 and n" 379 it was
moderate (m.), while that in the water-cultures of n" 410 — 436 is given
in the table. c. The date the experiment was brouglit to an end.
d. The results then stated : sub 1 the number of the stages of divi-
sion per 100 green chlorophyll corpuscles; sub 2 the concentration of
these corpuscles in the part wliich had been examined; sub 3 the
total increase (-[-) or decrease ( — ) or the equalness (0) of the whole
mass (here = the whole number')) of these corpuscles, calculated (per
unit of volume) from the colour-clianging ^) ; all this, concerning the
corpuscles present in the sponges or in the water from the lake or
in that from the conduit, in light as well as in darkness. e. Whether
the sponge material had been taken from a Spongilla (sp.) or from
an Ephydatia (e.). /'. Some remarks.

As for the method of examining and comparing the concentration
of the chlorophyll corpuscles in the sponge tissue and in cultures,
see p. 81. We shall call this concentration in a green to dark green
sponge or membrane : strong (s.); that in a yellow-green to light-
green (gray-green) sponge or membrane: moderate (m.); that in a
colourless to greenish to light yellow-green sponge or membrane:
weak (w.) *).

All experiments are mentioned; those belonging to one series are
placed together in one space.

As for the discussion, see p. 54 — 56 and p. 77 — 83.

1) A3 Ihcir size in sponge tissue and water remains almost equal.

2) In the table -}- or — to an indication (eg. ni. + , Q- +-) mcans, Ihat the
quantity is somowhat greater or somewhat smaller, ihan the indication denotes by itself.

14

210

Tari.e 11. CvlUirrs of hoJoied grern cldorophyU eorpuscJes of
SfortgiUa in water, vu l/f/]il ar ir, darkness. Co7ïtparison of iltc rnini-
hcr of oildrops occvrriiifi frec in the cxiUnreH to that present in the
green corpuscles, with respect lo tJie m(ttiJ>er of green stages of divi-
sion and the nnmher of eolovrless corpvsrh's trithovl strneture pre-
sent in il ie ciilliire^.

In the chief experiment fn» 290) several other cultures have been
rnatje of one original culture, on two diflerent moments. These new
cultures ai-e indicated in the tables by braces proceeding from the
original culture. All these cultures were frojn time to time microsco-
pically examined as to oildrops etc. (pag. 13—15). The observations
concerning a same culture are united in the table by short lines. The num-
bers joined to the braces and lines indicate the time (in months)
between the two observations; 1. means culture in light, d. culture
in darkness. For each observation is mentioned: sub 1 the number of
the green chlorophyll corpuscles, sub 2 that of the green stages of divi-
sion, sub 3 that of the colourless corpuscles witliout structure, sub 4
that of tlie green ones containing an oildrop, sub 5 that of the free
oildrops; always the üumber present in the whole microscopic prepara-
tion. As for the meaning of I— XII, see pag. 14—15; as for the
discussion, pag. 86 — 87.

Table 12. The nnniher of oildrops per amoehoctjte in the tissues
in different stages of development (conf. Table 6) of green Spongil-
lidae front lig ld and in colonrless ones front darkness (may be also
from light); microscopically examined by means of ravel preparations
from newly captured living sponges (p, 12 — 15).

For Spongilla these observations are given in 4groups(conf. Table 6),
viz. for the tissue of 7. branch-topsi?. branch-bases 5. different gemmule
stages 1 sponge-disks; for Ephydatia only for full-grown tissue (Table 6).

In the tables is indicated: a. the month of the examination. h.The
number then stated : in column 1 the (average) number of oildrops
per amoebocyte, in col. 2 the number of the green chlorophyll corpuscles,
in col. 3 that of the green corpuscles containing an oildrop, in col. 4
tliat of the colourless ones without structure; in the last 3 cases the
number present in the whole microscopic preparation. On each hori-
zontal line the data concerning one sponge piece are given; sub 5
tho analyses of different pieces of a same sponge are indicated by
the same letters. Finally for eacli tissue group the data, concerning
all analyzed sponges together, are composed; this composition sim-
plihes of course tlie mutual comparison of the results of the different
groiips. As for the meaning of I — XII, see pag. 14; as for the dis-
cussioii, pag. 85, 87-89.

Table

11.

n" i

2

3

4

5

1

2 3

■

4

5

i

2

3

4

5

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5

fl-i

X

IV VIII

X

VII

-i

X

III

V

X

VII

_1

X

III

VII

X

VII

-3

XII

VII

X

X

-2i

XII

1

VII

X

V

1-i

X

VI VIII

X

III

-i

X

III

VI

X

III

— i

X

III

VI

IX

III

-3

X

Vil

IX

IV

-2i

X

I

VII

X

IV

290 X

V

IX

VII

II

1-f

X Ivii VIIl

X

II

-i

X

lll

IV

X

III

— i

X

I

V

X

III

— 3

X

VII

X

VII

-2^i! X

I

VII

X

111

1. „

d|

X

III

-i

IV

X

IV

— 1

X

1

I

IX

III

— 3

X

III

X

III

-1l~ X I 111 IX III

1

1

Id.è

X

III

-4

V

X

IV

— 1

X

III

VI

IX

VI

— 3

X

III

X

Vil

•-2Ï

X

I III, IX, IV

¥

1-1

XII

VIIl

IV

IV

XII

III

I

XII

IV

— 3

:x

I

III

X

IX

-2i

X

X

IV

i

1

!•*

XI

VI

X

IX

— -1

X

I

I

X

IX

— 3

X

I

IX

IX

-2i

IV

IV

IV

'

X

V

II

1

X

IX

1-1
1.^

X
X

l
I

X
X

IX

IX

— 1

IX

VIU

IX

IX

— 3

— 3

X
X

I

X

IX

IX
IX

i

1
1

i-i

X

IV

X

IX

— i

VIII

VI

-3

1

I

X

IX

-2i

I

I

X

X

1;

Y

bi

X

V

X

IX

- 1

VII

vil

— 3

X

vil

IX

jiXII

VI)

III

II
I

IV

IV

XII

IV

VIIIIII

j

309 X

VI

1
vil IXj

i--i

■

xn VII IV

vil

IV

-0

XII

III

VllI

XI

VI

: i 1

310;; X

VI

VII

IX

1-1

xirviii' VI

vil

IV

— 6

XII

1

III

XI

X

\

31 li' X

VI

VII

IX

i.-l

!XII VIIl IV

VII

V

— 6

I

I

I

I

III

i

1

312 j X

VI

VII

IX

i-f

XII, V VI

X

IV

-6

I

I

VI

I

V

313:' X

I JVI j VII

IX

d.-f

XII UI I

XI

IV

1-6

VI

VI

vil

V

'

314J X

I jVIj VII

IX

XII| III jIII

XI

III

-6

VII

VIIl

III

315jj X

VI

VII

IX

d.-i

jxii

III

I

XI

V

— 6

XII

I

V

XI

X

-

316 X

VI

VJI

IX

d--|

XII

I

IV

XI

IV

— 6

X

I

VII]

vil

vil

210

Tabi.f. 12.

Spongillae.

green ones from light

colourless ones from flarkness

Spongillae.

gieen ones from liglit

colourless ones from darkness

Vil

VIII
VI
IX
IV
IV
IV
IV
VI
Vil
VI
VII
VI

XII
XII
XII
XII
XII
XII
XII

X

XII
XII

X
XII

VII
VII
VII
VII
VII
VIII
VII
VIII
VIII
VIII
IX
VII

VII

+

% +

+1= s

VI

VI

IX

VI
IV
IV
IV
IV
IV
VII
VII
VII
VI
VI
IV
VI
Vlll
VI

vin

VII
i VII

Ivi

IV
VII
VIII
VI
VI
VI
IX
IX
VI
VI
iVlIl
Vlll
IV
IV
VII

vil

XII

X
XII

X

X
IX

X
XI

X
X
X

vil

X

IX
X
X

IX
VIII

X
VIII

X

X

X

V

X

X

X

X

X

X

X

IX

X

IX

X

VII
VIII
VIII
VIII
VIII
Vlll

VIII
IX

VIII
X
IX
IX
X
X

bD r- b*; I

+ +Z

X £; >

c?i CT i-^

g^ — (N m •*

VII

+

t> « E

+
x •*
+ s

+ + X

f*^ ^ IC

VIII

IX

, to

4:

-TH (M ?0 'ïl'

IX
IV
IV
IV
IV
IV
VI
X

VIII
VI

VII
X

VI
VII
VII
VII
VII
VIII

VI
VI
VII
IV

III

IV
IX

III

IV
VII
VII
VIII
VII
VII
IX
X
VI
VIII
X
IX
X
IX
IV
IV

IX
IX
Vlll
XII
IX
IX

IX
IX
X
IX
IX

X 'i

+

X

^.+

+ > -

VIII

IX
XI
XII
XII
XI
XII
XII
XI
XII
XI

2 1=1 co

S 3 'o "o "o
*^ tj> ü i:j <:j

+

X

+ .

A «

tm
o

oa

> >>x
_; ^ -^ ló

"^ ^ - fc ■<

++++

C8

o o o c

'^ o -^j u

XI

IV

VII

XII
XII
X
X
X
X

X

XI
X

VII
VII

III

VII
X

VIII
IV
IV
IV
IV

X
X
IX
IX
IX
IX

X
X
X
X

XII

I

IX

IX

VII
VII

X
X

' young gemm.
■ olcler gemm.
> old gemm.

newly gcrmiii.

gemm.
later

later

XI

IV

still later

VIII
VI
VII

XII
XII

V
IV
VIII

XII
XII
XII
XII
X

young gemm.

old gemm.

newly germin.

gemm.
later

still later

VII
VII
Vil
VII
VI

' sponge-dislis

VII

XII
IV
IV
VII
IV

VIII
Vlll
VIII
VII
IX

spongc-disks

Epiiydatiae.

green ones

11

VIII

^

Vll

„

IV

„

VII

„

VIII

„

Vll

„

IV

„

IV

„

VI

I)

IV

1)

IV

IV

V

n

VI

n

VI

„

VI

n

VI

X
X
X
X

IX

X

VIII

IX

xu

X

IX
XII
XI
XI
X

x

X
X
X

IX
X
VIII
IX
XII
X
IX
X
IX
IX
IX
VII

VIII

VII
VIII

VII

IX
VIII

VII
VIII

VII
VIII
VIII
VIII

IX

IX
VIII

colourless ones

o
o

^XX

+ + +

^" X

5 • "^

co . T^
+ X X

„^a,co
.C+ + +

+ +

tO ^ S E P

-H £ !> K- l>

2 iri T^ T-' -*

rd

I CT CO ^

O o o o

VI

IV
IV
IV
IV
IV
VI
IV
VI
IV
VI
IV
IX
Vlll
VI
VII
IV
X
IV

V
IV
V

III

VI
VII

III
lil
II
II
II

V

III
III
II

V

IX

X

IX

IX

VIII

VIII

X

IX

VIII

VIII

X

XII
XII
XI
XI

X t:

+ -

X +

5 +

+t

•"• o . . .
A

. c^ co -*

211

Table 13. The preaoice of a lipase i)t the iissiie of Sj>o)if/illit.
In order to prove tliis presence I first made a sufficiënt quantitv
of pure emulsion of fat (oildrops) from the sponge tissue, in ti)e

following way:

A living Spongilla (green or colourless; or geramulae) is rubbed and
pressed, the parts of the skeleton removed; then tlie pressed out
hquid is centrifuged for about 5 minutes, by which a tliick niass (of
sponge cells and chhjro})liYll corpuscles) sinks to the bottom and the
Hquid remains. Tlie kitter contains numerous oildrops (and, niay be,
chlorophyll corpuscles). Next this liquid is evaporated at 60°; tlie
residue extracted by etlier; the ether then fdtered and evaporated
too. Then )-emains a substance of vaseline-like consistence, sticky,
with a strong sniell, nielting when warm and then forrning a lasting
greasy spot on paper, indissolu1)le in water, but dissoluble in ether
and xylol, stained red witli sudan III and black with osmic acid.
Consequently this substance is fat. By boiling in water it becomes
an emulsion again, containing the same oildrops we originally i)ro-
ceeded from. (Besides, tliis boiling is necessary to destroy all traces of
enzymes, that might still be present.) I shall call this boiled liquid
,, emulsion".

Next another living sponge is rubbed and pressed, etc, etc. (see
above); while the liquid, i'emaining after centrifuging, is kept. This
will contain the lipase, at least when it is present in sponge tissue.
This li(iuid I shall call „enzynie".

As one knows, tlie lipase splits the lat by hydrolysis into its com-
ponent parts: the glycerine and the acids. It is the arising of the
latter we have to sliow in our experiments; in the following way:
A certain quantity of ,,enzyme" and „emulsion" are mixed; to this
we add one drop of the indicator phenolphthaleine — being red in
alkaline milieu, but colourless in an acid one — and such a small
quantity of an (alkaline) Na^ CO3 solution that the whole mixture
becomes light-red. The acids, then, set free from the „emulsion" by
the lipase will make the red colour disappear. In order to get a pure
result it is necessary, however, that in this mixture no acids arise in
another way than by the hydrolysis due to the lipase; or at least
that we reckon with it, if it proves to be the case.

3 Series of experiments (I, II and III) were made at the same time,
in which the following substances were mixed:

I. 15 drops of „enzyme" + '2.5 cM* of „emulsion" +1 drop of phenolph. + Na^ CO3 sol.
II. 15 drops of „enzyme" -f 2.5 cW of water + 1 drop of phenolph. + Na^ CO3 sol.

ÜI. 15 drops of water + 2.5 cM-' of „emulsion" + '1 drop of phenolph. -{- Naj CO3 sol.

/

212

Tlie experiments were kept for liours at the same temperature as the

room. Meanwhile the colour was accurately examined; while I used the

foliowing indications for tlie red tint, arraiiged according to decrea-

sing intensity : light-red >• somewhat red > reddish >■ somewhat

reddish > colourless. In tlie table we find tlie colour-changings re-

gistered; the data concerning one experiment, obtained at the times

indicated, are given on one horizontal line.

1 ^ i

F— .

to

w 'S cc
tn "O co

CO n3

to is r-r

2 -

to -o "^ -

oj a> m

03 P -S

03 03 «

1—1 '"' ^

T! ^ ^ ^ ^ 'u

3 - . <-■ 1
O ^ "O j

^ T

3 P p P *> P ^

"o ^ "o

. — c > 03

-3 bc &

o (U Ü

U 03

Ü F^ ^ ^

s

a

S "

o

o

o

co

to

Wl

g

a

d P :;:;:: ::

ji p p p

PhPPPPPPP

■^-"

co

rH|N

ri

co

Xi

1^

to ï-1
co

^ ^
^ ? ^ ï

'O .- .- .-

co

'■^ ^ -r :^ -G ^

T3 -a 03 -

03 -|J

0/ 03 to _ ' "^

03 03 —

— ' c3

f" ^

o 1?

'T! ■ <U '

8 a

o

CA

I-i's 1

o ? -^ fl

-a P p p 'S
■a 1^

m 03 ... ^

u a ' ' "

t .'i' ^ .

o 03 ;:?

5 « p p p" a

a °

o

o

CO

co

S

s

a

a

p^pprrr, p,..r

j^ppppppp

r^\it

ei

g4

CÓ

^

co

jz

CC

-Ö -ö

'S

■ö S" oi Td

-a ^3

-a

-Ö

13 "tHOJ 'OJtDPr'H'

03

T *- V '" " '" '" '1

-^ ? C3 J. -

tj PfPPPPP

-*^ PPPPPPP

■a xi ^

rC

.0

jC

öC ^ ^ bc

^

_U)

.SP

— ' « " ii;

*.-.•..

^^

^iH

a

g - ' -

o

o

M

to

a

s

a

a

o. P ;; p :: f;

oj p p p

03 p P r- p p .r ?

dippppppp

^

-r^

T-i

ï6

■^

^H

Cl M o 1- .- .-*

-l* ifl C* (N

1— ( 1— 1 1 — II — 1

JJS^lS^o-n»

t— ( *— 1

1— 1^ h- II— 1^.'— ( 1— i^r-^r-^

I-H

1-1 1 >-i i-i

1— 1 1— (

j_"

Ih ^

^

03

03

03

03

D-;;r.rrp' a^pfr

a.ppppppp

O-PPPPPPP

!«! X

x

X

03

Cj

03

03

Table 14.

water of canal

water of lake

water from conduit 1

green sponge

colourl. spoDge

remarks

green sponge

colourl. sponge

remarks

green sponge

colourl. sponge

remarks

oildr.

glob. I

oildr.

glob. I

oildr.

glob. 1

oildr.

glob. I

oildr.

glob. I

oildr.

glob. I.

1

2

i

2

i

2

i

2

1

2

1

2

i

2

1

2

1

2

1

2

i

2

1

2

IX

IX

IX

IX

IX
IX

s. IX.

1 day in aq.

IX
X
IX

IX
X
IX

s. IX.

i day in aq.

X

X

s. IX.

reduct. ?

li month in aq.

VII

VII
VIII

VIII

IX

VIII

IV
XII

VII
XII

s. VI.

1 day in aq.

VI
IV
VII
VI
VI

VI
VI

vm

VII

vil

X
IX
VII
IX

X
X
X
IX

s. VI.

1 day in aq.

VI

VII

X

X

IV

VI

XII

XII

e. VI.

i day in aq.

IV

VII

Vlll

VIII

X

IX

X

X

e. VI.

I day in aq.

VI
IX

VII
X

XII

XII

XII
XII

X

XII

XII

XII

s. VIII.
not in aq.

IX
VI

X
VIII

XII
XII

XII
XII

VI

X

XII

XII

s. VIII.
not in aq.

VI
VIII

X
XII

X
XII

X
XII

Vlll
X

XI
XII

X
XII

X

XI

s. VIII.
no reduct.
1 month in aq.

VIII
IV

XII
VIII

X
X

X
X

IX
X

XII
XII

X
X

X
XII

s. VIII.
no reduct.
5 days in aq.

IX
IV
IV

XII
VIII
VII

XII
X
X

XII
XII
XII

s. IX.

no reduct.

J month in aq.

1

IV

VII
VII

VI

IX

VIII

X

XII
XII

X

XII

xn

s. IX.

no i-cduct.

1 month in aq.

213

I sliould inention that the colours of I^, II^ and IIIj were absolutely
equal at the beginning of the experiment; this was also the case in
I3 — I,,, II3, II4, III3 and III j as well as in I,., — 1,5, II-, 11^, III5 and
Illg. The experiments I3 etc, II3 etc. and III3 etc. contained other
,,enzyme" and ,,emulsion" than the preceding ones.

In the first place we see from the table, that the ,, blind" experi-
mental series II and III lose indeed more or less their red colour.
Consequently, acids are set free in these. In II one might ascribe
this to liydrolysis due to tlie lipase, for this mixture must have also
contained some (few) oildrops. But in III no lipase can have been
present at all; nevertheless the fat is hydrolyzed — probably by means
of the alkali — (or the red colour diminishes by the entrance of COj
from the air).

The expei'iments of series I, liowever, prove to lose their red colour
sooner than those of II and III. One might be inclined to explain
this by tlie combined inüuences, which were acting separately in II
and III. But that would not be exact, as is shown in the second and
in the last group of experiments. Still another factor must have been
acting. That must be the hydrolysis of the fat by the lipase. But
this lipase does not seem to be very active here; although it is ditfi-
cult to give a decision.

Table 14. Th^ Huinher of oildrops mid of' glohules, tolticli eau he
stained (hrovm) hy 7, present in choanocytes in comparison to that
in anwehocytes^ in green and coJourless Spongillidae taken from
ivater of tlte lake, from water of the canal and from that of the
conduit ; microscopically examined by means of ravel preparations
(p. 12 — 15) of sponge tissue.

I examined green Spongillae (s.) and Ephydatiae (e.) from light and
colourless ones from darkness. The (average) number of oildrops
(oildr.) and of globules which can be stained by I (glob. I) wasalways
stated in the same volume of amoebocytes (sub 1) and of choanocytes
(sub 2). As for the meaning of I — XII, see pag. 14. In the column
,,remarks" is mentioned: the. species of the sponge; the month of
the examination; whether the sponges, after their capture from the
lake or the canal, had been in water from the conduit (aq.) before
they were examined, and for how many time; and whether sponge-
reduction had occurred.

All experiments are mentioned. As for the discussion, see pag. 90 — 93.

214

Table 15. The numher of amoebocytes, containing food-vacuoles,
present in the (ravel) preparation (p. 7t^ — 15) of green and colour-
less Spongülidae (hefore, and after they Jiave heen cultivated in
aquaria) froni light and- from darkness, in tissues in different stages
of developynent (conf. Tahle 6).

Immediat.ely after the capture of green Spongillae from light and
colourless ones from darkness their brancli-tops and branch-bases
were examined as for their amount of amoebocytes containing food-
vacuoles; of Ephydatiae only the fuU-grown tissue was studied (conf.
Table 6). After some weeks' culture in water from the conduit in
light or in darkness this examination was repeated, tlien, only for
fuU-grown tissue. Generally of each sponge a piece was cultivated in
light and another one under equal circumstances in darkness. As
for the meaning of I — XII , see p. 14. The total number of amoe-
bocytes present in the preparation was always very nurnerous (XI).

In the table is indicated: a. The n" of the experiment, h. The date
of the examination. c. The then stated number of amoebocytes con-
taining vacuoles present in the preparation of a branch-top (t.) or a
branch-base (b.), for cultures in light or in darkness; viz. on the 1^'
line the number immediately after the capture (so at the beginning
of the experiment) and on the 2'"! the number at the end. Finally
for each tissue group the data, concerning all analyzed sponges together,
are composed.

All observations are mentioned, The green Ephydatiae came from
tlie light, the colourless ones from darkness or from the liglit. As for
the discussion, see pag. 94.

215

Table 15 A.

Spongillae.

green ones from light

colourless ones from darkness

cultures in

cultures in

light

darkness

light darkness

no

date

t.

b.

t.

b.

nO

date

t.

b.

t.

b.

292

23. VII

VI

I

I

IV

298

25. VII

Vil

IX

IV

IV

17. VIII

VII

IX

'10 VII 1

IX

IX

293

23. VII

I

VII

I

VII

299

26. VII

III

III

IV

IV

17. VIII

VII

VII

16. VIII

IX

VII

294

24. VII

1

VI ' III

IX

19. VIII

X

IX

VIII

1

-

367

22. VI

VI

11. VII

VII

.VII

N

a

23. VII

III

VI

i

23. VII

II

b

III

III

,i

III

VII

c

VI

k

VI

d

VII

1

IV

IX

e

IV

VI

m

IV

vil

f

51

III

vil

n

VI

IV

g

III

VI

0

,,

VIII

vil]

h

„ [IV

III

P

VI

VIII

together; results of newly captured sponges

lops :
4.1 + 5. III + 2. IV + 1. VI

tops :
1. II + 2. III + 4. IV + 3. VI +
+ 1. VII + 1. VIII

bases :

bases :

1.1 + 2. III + 1. IV + 6. VI +
+ 4. Vil + 1. VIII + 1. IX

1. III + 3. IV + 2. VII + 2. VIII+ 2. IX

216

Table 15 B.

Ephydatiae.

green ones

colourless ones

cultures in

cultures in

liglit darkness

light darkness

n"

date

t. 1 b.

t.

b.

11"

dato

t.

b.

t.

b.

333

23.11

III

III

336

24.-1 1

IV

IV

I.V

VII

IV

I.V

V

IV

334 •

23.11

III

V

.337

24.11

IV

IV

30. IV

VII

IV

7. V

IV

IV

3.39

25.11

III

IV

338

24.11

IV

IV

24. IV

VII

X

8.V

IV

IV

340

25.11

IV

III

.341-2

25.11

IV !

IV

23. IV

III

III

30. IV

VII

IV

343-4

26.11

IV

V

345-6

26.11

IV

.V

30. IV

IV

VII

30. IV

IV

IV

348

26.11

IV

.347

26.11

IV

8.V '

X

7.V

IV

3661

21. VI

IV

IV

365 1

20. VI

III

III

12. VII

IV

IV

10. VII

IV

VII

36611

21. VI

III

IV

365 II

20. VI

III

IV

13. VII

VII

IV

10. VII

VI

VII

together; results of newly c

aptured sponges

6.111 + 7. IV + 2. V

3. III + 11. IV + I.V

ILLUSTRATIONS.

EXPLA.NATION OF PLATES n" I— VI.

Fo)- clearness' sake many figures have been drawn more or less dia-
grammatkally from nature. For each object (.„symbioiic" alga, flagellated
chambei\ etc), however, at least one illustration true to nature lias always
heen given.

Fig. 1. Living green Spongillae lacustr. in water (natural size). The sponge-
crust cannot be seen. As for the discussion, see p. 15—16.

Fig. 2. Living colourless Spongillae lacustr. (natural size) in water, show-
ing oscular tubes. The sponge-crust cannot be seen. See p. 15 — 16.

Fig. 3. Living Spongilla growing on coverglass (magnif. 4 tiraes). i. = old
centre; 2. = newly formed membrane. See p. 12 — 13.

Fig. 4. Isolated living amoebocyte of Spongilla grown on coverglass (magnif.
± 1000 times). nu. = nucleus; gr. alg. = green chlorophyll cor-
puscles. See p. 17, 175.

Fig. 5. Living green chlorophyll corpuscle of Spongillides (= „symbiotic"'
alga). Magnif. ± 6600 times. ch.p. = chloroplast; odr. = oildrop.
See p. 24 — 25.

Figs. 6 — 11. Plasmolysis in the „symbiotic" algae of Spongillidae. The hea-
vily dotted portion represents the chloroplast; the slightly dotted
one the protoplasm. See p. 26.

Figs. 12 — 31. Different stages of the living green „symbiotic" algae of Spon-
gillidae. Figs. 16—22, 25—29, 31 stages of division. The dotted
portion represents the chloroplast. See p. 24, 30—33.

Figs. 32 — 34. Plural stages of division of the green „symbiotic" algae of
Spongillidae. The dotted portion represents the chloroplast. See p. 33.

Figs. 35 — 37. Colourless stages of the „symbiotic" algae of Spongillidae.
Fig. 35 represents a „colourless alga with clear structure" ; Fig. 36
a „colourless one with shade of structure"; Fig. 37 a ,, colourless
one without structure". See p. 36, 42.

Figs. 38 — 42. Green „symbiotic" algae of Spongillidae lulled, and stained
by methylene-blue or haematoxyline. In Fig. 38 and 39 the oildrops
have been stained. See pag. 25 — 26.

Figs. 43 — 45. Filamentous algae infecting Ephydatia (magnif. ± 350 times).
See p. 117.

Figs. 46 — 52. Unicellular alga' infecting Ephydatia (magnif. + 800 times).
The dotted portion repi'esents the chloroplast. See p. 117.

218

Fig. 53. Diagraminatic representation of a section of the body wall of Spon-
gilla (with few alterations after Delage and Hérot-ard). cnli. =
conukis; p. = ostia; os. = osculuin; ox.t. = oscular tube; ects.
= ectosome; cv. hij. = subdermal cavity; en. inh. = incurrent
canal; cn.exh. = excurrent canal ; c/^s. = parenchyma ; the arrows
indicate the direction of the water current. See p. 119 — 120.

Fig. 54. Fiagellated chambers and surroundings in Spongilla. fl. ch. =
flagellated chamber; inc. can. = incurrent canal; exc. can. =
excurrent canal. Magnif. ih 130 times. The arrows indicate the
direction of the water current. See p. 120.

Fig. 55. Section of a flagellated chamber of Spongilla (magnif. + 1600 times),
after Vosmaer and Pekelharing, ap. = apopyle. See p. 120.

Fig. 56. Successive stages of the flagellar movement of an isolated choa-
nocyte. The cell body is still connected with several other choa-
nocytes, the collar is entirely retracted. The arrows indicate the
direction of the water current, the dots floating particles; the
moment of observation is given in each case; a. immediately
after isolatiou; in e. the flagellum bas finally come to rest. Magnif.
rb 1770 times. See p. 126—127.

Fig. 57. As Fig. 56. The collar is partly retracted. a. immedately after
isolation; in c. the flagellum lias come to rest; in d. — e. a (new)
period of weak motion began again, which is fmished in /". Magnif.
± 1770 times. See p. 128.

Fig. 58. Successive stages of the flagellar movement of a number of cho-
anocytes still joined within a part of a flagellated chamber,
observed in a i"avel preparation. The collars are entirely retracted.
a. im-mediately after isolation, in c. the flagella have finally come
to rest. Cnf. Figs. 56—57. See p. 128, 132.

Fig. 59. Intact tlagellated chamber of living Spongilla grown on cover-
glass; the flagella in the normal spiral- or undulating-niotion.
The collars are fuUy expanded. ch.l. = choanocytic layer; odr. =
oildrops. Magnif. ± 1430 times. See p. 130 — 131.

Figs. 60 — 62. Representation of flagellum and collar seen on top; in Fig. 60
the tlagellum stops, in Fig. 01 it is in spiral-motion, in Fig. 62 in
flat undulating-motion. See p. 131 — 132.

Fig. 63. Diagrammatic representation of the water current inside a flagel-
lated chamber of Spongilla. pr.p. = prosopyle; ap.p. = apopyle;
the arrows indicate the direction of the current; + and — refer
to the water pressure. See p. 132 — 134.

Fig. 64. Semi-diagrammatic rei)resentation of a chamber, the flagella of
which are beating with the tops outside the apopyle. ch. l. =
choanocytic layer. See p. 135 — 136.

Fig. 65. The dill'erent ways of capturing (food-)particles within a flagel-
lated chamber of Spongilla (diagrammatic). The prosopyles have
not been drawn, nor the separate cells of the choanocytic layer
(c/l. l.). The way taken by the particles is indicated by dots.
a. and b. show the capturing between the bodies of the choano-
cytes; c. the capturing between the collars; d. the capturing at
the bases of the collars, See p. 143—145.

219

4

Fig. 66. The capture of (food-)particles witliin a flagellated chamber with
2 pi'osopyles, viz. between the bases of the collars of the choano-
cytes (semi-diagrammatic). The way taken by the particles is
indicated by dots. Tlie separate cells of the choanacytic layer
(ch.l.) have not been drawn; the layer contains numerous particles
w'hich have been captured. Magnif. ± 1000 times. See p. 143 — 146.

Figs. 67—68. The capture of a carmine grain between 3 collars (Fig. 67),
and the descending of the grain along a collar to the base (Fig.
68, 1 — 2) (semi-diagraminalic). See p. 145.

Fig. 69. A flagellated chamber and its surroundings in a living green Spon-
gilla grown on coverglass (magnif. ± 800 times). gr. alg. = green
.,symbiotic" algae; cl. alg. = colourless „symbiotic" algae; ch. l.
= choanocytic layer; mesgl. = mesogloea; ai)i. = amoebocyte;
nu. = nucleus; vac. = food vacuole; odr. = oildrops. By 1 — 2 — 3
is represented the ejection of „symbiotic" algae by the choano-
cytic layer into the mesogloea. See p. 16, 147, 174.

Fig. 70. Two carmine grains (a. and b.) ejected from a choanocytic layer
(ch. l.) into a parenchymal tissue-bridge (semi-diagrammatic).
In I the original condition is given; in II grain o. was ejected
and moved on (i — 2 — 3—4 — 5), in III grain h. ejected and moved
on {i— 2— 3-4-5— 6—1). See p. 147.

Fig. 71. The spreading of carmine from a flagellated chamber through
the mesogloea into the amoebocytes. ca. = carmine grains and
conglomerates ; the other indications as in Fig. 69. Magnif. ± 800
times. See p. 147—148, 174.

Fig. 72. The layer of apparently undiiferentiated flowing plasma {pi. l.)
situated outside and against the base of the choanocytes {ch. l.);
an oildrop is moved on slowly (i — 2—3). See p. 151 — 154.

Fig. 73. Semi-diagrammatic representation of a flagellated chamber with
the layer of flowing protoplasm (pLl.) lying against the choano-
cytes at the side of the incurrent canal. The choanocytic layer
(ch. l.) has been drawn -as one vvhole; it lodges numerous captured
carmine particles. Similar particles are carried along in the plasmic
layer (i — 2 — 3) to a deposit place, from where now and then a
large (fecal) conglomerate is ejected. Magnif. + 1000 times. See
p. 151—154, 166—168.

Fig. 74. Three flagellated chambers and incurrent canal {can.)\ layer of
flowing plasma against the base of the choanocytes at the side
of the canal; tissue ., bridge" bent through the canal (semi-diagram-
matic). The figure represents the transport of carmine in the plasmic
layer (a—fe-c) and in the „bridge" (/— 2— 3—4— .5). c/(. /. = choa-
nocytic layer; ca. = carmine (grains and conglomerates) which
has been captured. See p. 151 — 154.

Fig. 75. The capture {2) and the carrying aside (3—4) of a coarse (food-)
partiele, that remained sticking in the prosopyle (1 — 2), by means
of the layer of flowing protoplasm (pi. l.). The figure is semi-
diagrammatic. The separate cells of the choanocytic layer (ch. l.)
have not been drawn; the layer contains numerous particles which
have been captured. Magnif. + 1000 times. See p. 152.

220

Fig. 7ü. The defecation and excretion by a vacuole situated in the canal
wall. The small circles represent green «symbiotic" algae. Mag-
nif. ± 400 times. See p. 163—164.

Fig. 77. The protruding and withdrawing of a defecation (and excretion)
vacuole at several canals; in 1. a vacuole has not yet been formed ;
in 4. it finally protrudes into the 3"^ canal and bui'sts. Tlie small
circles represent green „symbiotic" algae. Magnif. rb 400 times.
See p. ie::;— 166.

Tijdschnft der Ned. Dierk. Vereen., 2de Serie, Dl. XVII.

Van Triot photogr. et del.

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II. VERSLAGEN.

GEWONE HUISHOUDELIJKE VERGADERING.

Sneek. Hotel de Stad Munster. Zaterdag 29 Juni 1918. 's Avonds

halfaclit uur.

Aanwezig de Heeren: Sluiter (Voorzitter), de Beaufort van Bem-
MELEN, BoscHMA, Ihle, Loman, Redeke, Romijn, Weber en de Dames:
Rastert, de Lint, Weber-van Bosse, Wibaut-Isebree Moens. Als gast

Mevrouw Redeke-Hoek. » /-, /-v '

Afwezig met kennisgeving de Heeren: van Kampen en A. G. üudemans.

De Voorzitter opent de vergadering en heet de leden welkom. Ver-
volgens verkrijgt de secretaris het woord voor het uitbrengen van het
jaarverslag.

Jaarverslag van den secretaris.

Het is mij opnieuw een aangename taak aan Uwe vergadering ver-
slao- uit te brengen over den toestand onzer Vereeniging, thans over een
tijdvak, dat zich uitstrekt van 23 Juni '1917 tot dezen dag.

De samenstelling van het Bestuur onderging geen verandering, in de
Redactie-Commissie voor het Tijdschrift werd de Heer Loman herkozen.
Door den dood ontviel ons in Augustus 1917 van onze leden de Heer
Dr H J. Veth, die aan onze Vereeniging 'j, gedeelte van zijn vermogen
naliet, welke nalatenschap voorloopig nog met vruchtgebruik bezwaard
is. In de vergadering van 29 September 1917 werd door den voorzitter
dank gebracht aan den overledene voor zijn milde gave. , , ,,

In 1917 hebben 14 dames en heeren voor hun lidmaatschap bedankt
en wel de Dames Kleyn, Jonker, Cool, Sabron, Schoneboom, le Vino
en de Heeren v. Ameyden, Crèvecoeur, Backhuys Everts, RJSink
Heymann, Ootmar en Hammer, zoodat het aantal leden emde 191 / tot
209 daalde

In 1918 "traden slechts 7 nieuwe leden tot onze Vereeniging toe tegen
15 in 1917. Deze geringe aanwas staat waarschijnlijk in verband met
het feit, dat de Regeering in de laatste jaren geen subsidie meer ver-
leent aan de studenten, die het Zoölogisch Station te Helder bezoeken.
De nieuw toegetreden leden zijn de Dames: Brouwer, Berghege,
ScHiJFSMA, en de Heeren: Reijne, v. d. Woude Venema, Varossieau en
Begemann. Onze Vereeniging telt dus thans 209 leden tegenovei 21b
ten tijde van de huishoudelijke vergadering in Jum 1917. Er is dus een
kleine achteruitgang waar te nemen.

tt

De vergaderingen werden op de gebruikelijke wijze geliouden. I)e ge-
wone huishoudelijke vergadering had 23 Juni 1917 plaats te Oisterwijk
in het gebouw der Oisterwijksche Schoolvereeniging, voor dit doel wel-
willend door den Hee)" Georgf: Pehk te Oisterwijk tot onze beschikking-
gesteld. In deze vergadering werd de Heer Loman herkozen als lid der
Commissie van Redactie voor het Tijdschrift. Op den dag dezer verga-
dering hield Dr. J. Lorié, uitgenoodigd door liet Bestuur, in het gebouw
der Oisterwijksche Schoolvereeniging een voordracht over ,,de Vennen
in liet algemeen". Deze voordracht vormde de inleiding tot een welge-
slaagde excursie naar de vennen te Oisterwijk, die Zondag 24 Juni onder
leiding van de Heeren Dr. J. Lorié en Dr. J. T[i. Oudemans gehouden
werd. Alle wetenschappelijke vergaderingen liadden wegens de beperkte
treinenloop plaats te Amsterdam in de kleine restauratiezaal van het
Koninklijk Zoölogisch Genootscha]) „Natura Ai'tis Magistra", daarvoor
ook thans weer welwillend door het Genootschap afgestaan, en wel de
Isie vergadering op 29 September 1917, de 1'^^ op 24 November 1917,
de S'ie op 26 Januari 1918 en de 4'^« op 27 April 1918.

Van het Tijdsclnlft zag aflevering 1 van deel 16 in September 1917
het licht, terwijl een dubl)ele aflevering 2 en 3 deze maand versclieen.
De Redactie-Commissie zag zicli in overleg met het Bestuur tot haar
leedwezen wegens geldgebrek genoodzaakt alleen die verliandelingen op
te nemen, waarvan de auteurs bereid zijn de kosten te dragen van het
zetten van den text en het maken der clichés. Om dezelfde reden ging-
liet Bestuur, hoewel noode, er toe over de abonnementsprijs op het Tijd-
schrift voor de leden van ƒ 3.50 tot /"5. — per deel te verhoogen.

Daarna brengt de heer H. C. Redeke het volgende verslag uit:

Verslag over den H y d r o b i o 1 o g i s c h e n C u i' s u s.

Omtrent den tweeden Hydrobiologischen Cursus, die van 23 — 29 Juni
1918 te Langweer in Friesland werd gehouden, zij het volgende mee-
gedeeld.

Zeer tot ons leedwezen heeft MejuÜrouw Scholten gemeend als lid
der Commissie te moeten bedanken. In haar plaats werd Professor van
Bemmelen benoemd, die zich evenwel, na aan de voorbereidingen een
werkzaam aandeel, te hebben genomen, jammer genoeg eveneens ge-
noopt zag, wegens drukke ambtsbezigheden ontslag te nemen. De Com-
missie vond ten slotte Mevrouw Dr. Wibaut-Isebree Moens bereid als
lid tot de Commissie toe te treden en de leiding van een der dagen op
zich te nemen. Ingevolge hiervan moest het programma eenige wijzi-
gingen ondergaan.

Voor het praktisch werken werd een geschikte gelegenheid gevonden
in de bovenzaal van het liótel der dames Mink, genaamd: ,,Het Wapen
van Doniawerstal", terwijl de Heeren D. van der Ley, wethouder en
A. Faber, notaris, beiden te Langweer, de Commissie aan zich verplicht
hebben, door voorlichting en hulp bij het verkrijgen van de noodige
zeilvaartuigen voor de excursies. Daar tijdens den duur van den cursus
het drijvend visscherij-laboratorium ,, Meerval" te Langweer gestation-
neenl was, kon van de wetenschappelijke en andere hulpmiddelen aan
hooi'd bij verschillende gelegenheden i'uimschoots gebruik worden gemaakt.

Twaalf dames en heeren hebben zich voor den cursus aangemeld,
en wel: de Heer W. Pï. van Seters, phil. docts., 's Gravenhage ; de
Heer H. C. Siebers, phil. docts., 's Gravenhage; Mejufl'r. J. Brouwer.

Til

phil. stiid., 'sGraveiiliage; MejuflV. B. Kaiser, Groningen; MejuÜr. J,
VoiGT, pliil. doct'^. Leiden; Mejulïr. Clm. Berkhout, i)liil. cand., 'sGra-
venhage; Mejuffr. Greta Jonges, phil. stud., Haarlem; Mejuffr. A. Haga,
phil. stud., Groningen; Mejuffr. B. Immink, phil. doet''.. Leiden; Mejuffr.
C. R. Bakker, pliil. cand. Leiden; de Heer H. Begeman, phil. cand.,
Utrecht en de Heer L. G. M. Baas Becking, phil. stud., Utrecht. De
laatstgenoemde was evenwel door ongesteldheid verhinderd aan den
cursus deel te nemen.

Zondagmiddag kwamen de deelnemers te Langweer bijeen en werden
er 's avonds door den voorzitter welkom geheeten. Aangezien de Com-
missie er niet in geslaagd was, om voor dien avond een spreker over
de geologische en de hydrologische gesteldheid der Friesche Meren te
vinden, moest de voordracht over het onderzoekingsgebied vervallen. In
de plaats daarvan hield Mevrouw Wibaut een inleidende voordracht
over zoetwater-sponsen en -bryozoen.

Op de volgende dagen werden de verschillende excursies en voor-
drachten gehouden, waarbij evenwel tengevolge van het ongunstige weer
een paar maal van het oorspronkelijke programma moest worden afge-
weken.

Maandagmiddag demonstreerde Mevrouw Wibaut het in de buurt
van Langweer verzamelde sponsen- en bryozoen-materiaal.

De geheele Dinsdag \verd in beslag genomen door de biologische
oefeningen en demonstraties onder leiding van Professor Jordan, waarbij
'de deelnemers in twee groepen, ,,pasbeginnenden" en ,, meergevorder-
den" werden gesplist. Tot de laatste groep behoorden de dtimes en
heeren, die den cursus reeds voor de tweede maal bijwoonden en aan
wie in verband daarmede de bewerking van eenige moeilijkere capita
selecta was opgedragen.

Woensdag was de plankton-dag. Ofschoon de pelagische fauna en
flora der Langweerder Wielen lang niet de verscheidenheid van soorten
bevatte, als het Heumensche plankton in het vorige jaar, konden toch
onder leiding van Mejuflrouw de Lint en Mevrouw W^iraut de voor-
naamste bestanddeelen van ons zoetwater-plankton in typische exem-
plaren worden vertoond.

Des Donderdags hield Dr. Redeke een voordracht over de biologie en
systematiek van eenige zoetwatervisschen, welke gevolgd werd door een
cursorische bewerking van enkele vertegenwoordigers der Pe reiden en
Cypriniden.

Den daaropvolgenden, laatsten dag besprak Dr. Romijn aan de hand
van een rijk materiaal de systematiek en oekologie der Cladoceren.

Ofschoon, zooals reeds gezegd is, het weer niet bovenmate gunstig
was, is ook deze cursus over het algemeen toch wel heel geslaagd. Dit
is voor een niet gering deel te danken aan het onverstoorbare goede
humeur en de opgewektheid der deelnemers en deelneemsters — eigen-
schappen, die vaak bij biologen worden aari'getroflfen ! — en voor het
overige aan den ijver en de toewijding, waarmede allen zich van de
door hen vrijwillig aanvaarde, maar met dat al dikwijls inspannende
taak hebben gekweten.

Vervolgens doet de penningmeester de volgende Rekening en Ver-
antwoording omtrent het door hem in 1917 gevoerde fmantieele beheer.

IV

Rekening en Verantwoording van den Penningmeester.

Ofitvangsten.

i. Saldo van 1916, reserve voor de uitgave van het tijdschrift f 1159.81 ^
'2. Contributie der leden 1062.00

Zoölogisch Station

3. Contributie van begunstigers . .

4. Bijdragen van particulieren v. h.

Rijkssubsidie

Huur der lokalen bij den adviseur in gebruik ....
Bijdragen tot tijdelijke uitbreiding van de uitgave van

het tijdschrift

Terugontvangen voor geleverd Zoölogiscli materiaal
Legaten, schenkingen, rente

8.

9.

10.

Baten van het Zoölogisch Station

30.00

50.00

1500.00

1500.00

1592.50

446.35

72.62

130.00

f 7543.285

Uitgaven.
Rente en aflossing.

A. der leening 1889 /" 331.25

B. der leening 1895 «....„ 318.75

2.

3.

4.
5.

6.

7.
8.

/■

Exploitatie van het Zoölogisch Station

Bibliotheek

Onkosten , .

Tijdschrift „ 1681.05

650.00
3026.35
233.58
138.40

Verschotten van bestuursleden „ 157.31

Drukwerk „ 147.80

Vergoeding van] woninghuur a/d Directeur v/li Zool. St. ,, 600.00
9. Bijdrage voor het pensioenfonds van het vast personeel

van het Zoölogisch Station ,, 100.00

10. Saldo (reserve voor de uitgave van het tijdschrift) . . ., 808.79 ^

f 7543.2^

Deze Rekening en Verantwoording is door de Commissie, bestaande
uit de Heeren A. C. Oudemans en W. Warnsinck, onderzocht en goed-
gekeurd. De Voorzitter dankt de Commissie en stelt de vergadering-
voor de rekening eveneens goed te keuren en den penningmeester onder
dankzegging te dechargeeren. Conform dit voorstel wordt besloten.

Daarna dient de penningmeester de volgende ontwerp-begrooting in
voor het jaar 1919.

Begrooting 1919.
Ontvangsten.

1. Saldo over 1918 pr. mem.

2. Contributie leden f 1200.—

3. Contributie begunstigers

4. Bijdragen van particulieren voor het Zoölogisch Station

30.
50.—

5. Rijkssubsidie . „ 1500.

6. Huiu' der lokalen bij den adviseur in gebruik

7. Verkoop tijdsclirift . . .

8. Geleverd Zoölogisch materiaal

9. Rente

10. Baten van liet Zoölogisch Station

1500.—

„ 300.—
„ 80.—
„ 70--
f 4731.—

Uitgaven.

1. Rente en atlossing.

A. Leening 1889 f 31 8.75

B. Leening 1895 „ 306.25

'2. Exploitatie van het Zoölogisch Station

3. Bibliotheek

4. Onkosten

5. Verschotten van bestuursleden . . . .

6. Drukwerk

f 625.
2495.
300.
150.
100.
100.

7. Vergoeding van woninghuur aan den Directeur van het

Zoölogisch Station

8. Bijdrage pensioenfonds

9. Tijdschrift

10. Onvoorziene uitgaven

'b^

600.

100.

250.

11.

f 4731.

Ook deze begrooting wordt door de vergadering goedgekeurd.
Hierna brengt de Directeur van het Zoölogisch Station verslag uit
over den toestand dezer instelling in 1917.

'D

Verslag over den toestand van het Zoölogisch
Station in 1917.

Mijn verslag over 1917 kan kort zijn, aangezien er in het afgeloopen
jaar geenerlei bijzondere gebeurtenissen zijn voorgevallen.

Aan het onderhoud van het gebouw werd de noodige zorg besteed.
Veel stormschade maakte talrijke herstellingen aan het dak noodzakelijk.
De schietschade was in 1917 belangrijk, doch werd als altijd op de
meest voorkomende wijze vanwege het Departement van Marine vergoed.
Ook werd veel hinder ondervonden door het drukke gerij van zware
vrachtautomobielen langs de Buitenhaven. In de kleine vestibule werd
een oud windhok w^eggebroken, waardoor een flinke ruimte voor de
berging van rijwielen werd verkregen.

De inventaris werd op de gebruikelijke wijze aangevuld en uitgebreid
o. a. met een dienstrijwiel.

In verband met de steeds stijgende prijzen voor alcohol en chemica-
liën werd in den aanvang van het jaar van beide een extra-voorraad
ingeslagen.

Het aquarium vereischte geen bijzonder onderhoud. Alleen werd van
de zeewaterbuisieiding een koperen voetklep gestolen, die echter aan-
stonds door een reserve-klep kon worden vervangen, die vervolgens goed
opgesloten werd.

De motorvlet kon tengevolge van den benzine-nood zoo goed als niet
gebruikt worden.

Het aantal laboranten bedroeg acht, niettegenstaande ook in het afge-
loopen jaar geen subsidie beschikbaar was.

De Heer J. L. Addens, phil. drs. te Groningen, kwam van 19 — 21
April in het Station om materiaal van Bryozoen voor een proefschrift
over de ontwikkeling dezer dieren te verzamelen.

De Dames J. H. H. van der Meer, P. A. C. de Vos en Zuster Ro-
SALiE, leerlingen van de Amsterdamsche Universiteit, werkten van eind
Juni tot ongeveer midden Juli over plankton, wieren en visschen.

VI

De Heer G. L. Funke uit Utrecht vertoefde van 1 — 2'i Augustus in
het Station en hield zich met een algemeene studie der Heldersche
Kustfauna onledig.

Met hetzelfde doel kwamen de Dames A. G. Vorstman en E. M. J.
Koker, beiden van Amsterdam, achtereenvolgens van 8 — 19 en van
12 — 19 Augustus in het Station.

De verzending van materiaal had ook in het afgeloopen jaar wederom
op groote schaal plaats.

Zoo ontvingen:

Het Zoötomisch Laboratorium te Amsterdam : diverse haaien en Crus-
taceen, Kwalletjes, Avenicola en Parechinus.

Het Zoötomisch Laboratorium te Leiden : 40 stuks haaien en '2 buizen
Balanus.

Het Zoötomiscli Laboi'atorium te Groningen: 60 haaien, 18 stuks
A%)hrod\te en groote partijen scliaal- en schelpdieren.

Het Zoötomisch Laboratorium te Utrecht: diverse koppen van liaaien.

Professor Jelgersma te Leiden : drie bruinvisschen.

De Hortus Botanicus te Amsterdam: eenige manden zeewier.

De Hortus Botanicus te Utrecht: twee manden wieren.

Mej. Haga te Groningen: diverse wieren.

Dr. van Deinse te Rotterdam: 1 haai,"

De Heer Godsen te Amsterdam: diverse wormen en zeesterren.

De R. G. H. B. S. voor meisjes te Amsterdam en het R. C. Lyceum
voor meisjes te 's Gravenhage: elk een kleine collectie diverse zee-
dieren.

Mej. van der Meer te Amsterdam: een Sepia^ 3 zeeëgels.

De H. B. S. met 5-jarigen cursus te 's Gravenhage en de Rijkskweek-
school te Deventer: elk een kleine collectie diverse zeedieren.

Omtrent de geldmiddelen kan nog worden medegedeeld, dat de uit-
gaven in 1917 in totaal ƒ 3026.35 hebben bedragen, waarvan ƒ446.91
voor den Hydrobiologischen Cursus te Heumen en /' 2579.44 voor den
gew^onen dienst van het Zoölogisch Station. Deze post komt in haar ge-
heel voor op de rekening en verantwoording van den Penningmeester,
die reeds een onderwerp uwer besprekingen heeft uitgemaakt. Om te
kunnen beoordeelen, welk gebruik van het genoemde bedrag is gemaakt,
laat ik hier een overzicht volgen van de voor de exploitatie van het
Station alsmede voor den Hydrobiologischen Cursus in 1917 gedane
uitgaven.

L Exploitatie vau het Station.

A. Gebouw en terrein /' 500.65

B. Aquarium en vlet ,, 99.18'/2

C. Ameublement ,, 4. —

D. Overige inventaris ,, 121.56

E. Alkohol en chemicaliën ... • • ... „ 162.01 '/j

F. Zoölogisch materiaal • ,, 233.62*/2

G. Exi)loitatie in engeren zin ,, 527.01 '/j

H. Schrijfbehoeften „ 46.75

L Dienstpersoneel ,, 790. —

•K, Grondlasten enz „ 94.64

Totaal . . . /■ 2579.44

Vii

II. Hydi'ohiolof/ischc (hd'siix.

A. Drukwerk, programma's enz /' 73.20

B. Huur en tiansport van meubelen ,, 47. —

C. Vracht, aankoop van materiaal enz 48.75

D. Reis- en verblijfkosten der Commissieleden en van den
bediende • ■ . „ 277.96

Totaal . . . f 446,91

De Voorzitter dankt den Directeur van het Zoölogisch Station voor
het lutgebraclite verslag. Het finantieele helieer van den Directeur van
het Zoölogisch Station over 19i7 is evenals dat van den penningmeester
door de Commissie, bestaande uit de Heeren A. C. Oudemans en W.
Warnsinck onderzocht en accoord bevonden, waarom de Voorzitter
voorstelt den Heer Redeke onder dankzegging te dechargeeren.

Vervolgens komt de uitloting van een aandeel in elk der beide geld-
leeningen aan de orde. Van de aandeelen in de leening van 1,889, aan-
gegaan ten behoeve van den bouw van het Zoölogisch Station, wordt
N". 21 (staande op naam van den Heer Prof. G. A, F. Molengraaff,
Delft), van die in de leening van 1894, gesloten voor de vergrooting van
het Zoölogisch Station wordt N". 16 (staande op naam van de Erven
van den Heer Dr. P. P. C. Hoek, Haarlem) uitgeloot.

Vervolgens heeft de verkiezing plaats van een secretaris in plaats van
den Heer Iule, die aan de beurt van aftreden is. De Heer Iule wordt
als zoodanig herkozen; ter vergadering aanwezig, verklaart hij zich be-
reid zijn herbenoeming aan te nemen.

Dan gescliiedt de verkiezing van een lid van het Bestuur in plaats
van den Heer van Kampen, die aan de beurt van aftreden is. De Heer
VAN Kampen wordt met algemeene stemmen lierkozen.

Op voorstel van den Voorzitter worden Mejuffrouw J. Scholten en
de Heer L. P. de Bussy benoemd tot leden der Commissie, belast met
het nazien der rekening en verantwoording van den Penningmeester en

i\.

van den Directeur van het Zoölogisch Station

Ten slotte wordt o]) voorstel van den Voorzitter besloten het volgend
jaar de gewone huishoudelijke vergadering te 's Hertogenbosch te hou-
den, waaraan een excursie naar den ,.LJzeren Man" verbonden zou
kunnen worden.

Bij de rondvraag deelt de Heer Romijn mede, dat Teyler's Genoot-
schap geld beschikbaai' heeft gesteld ten bate van het Natuurhistorisch
Genootschap voor Limburg voor het doen van een voorloopig onderzoek
van de hydrobiologie van de Maas.

Daarna sluit de Voorzitter de vergadering.

Zondag 30 Jimi liad onder leiding van den Heer Dr. H. C. Redeke
een welgeslaagde excursie naar Lang weer plaats, waar een bezoek
gebracht werd aan het drijvende laboratorium ,,de Meerval" van het
Rijksinstituut voor Visscherijonderzoek. Men vertrok 10.33 uit Sneek,
te Joure werd de lunch gebruikt, terwijl aan boord van de ..Meerval"
thee gedronken werd.

VIII

WETENSCHAPPELIJKE VERGADERING.

Amsterdam. Kleine Restauratiezaal van het K. Z. Genootschap ,, Natura
Artis Magistra". '28 September 19l8. 's Avonds halfacht uur.

Aanwezig de Heeren: Sluiter (Voorzitter), van Bemmelen, Bolsius,
I')OSCHMA, DE BussY, Droogleever Fortuyn, Druyvesteyx, V. D. Feen,
Heimans, V. D. Horst, Ihle, van Kampen, Kerbert, Loman, de Meijere,
Peeters, Romijn, Schuurmans Stekhoven en de Dames: Feltkamp,
FoRTUYN Droogleever, van Herwerden, Immink, Lens, de Lint,
ScHDFSMA, Scholten, de Vos, Wibaut-Isebree Moens.

De Voorzitter opent de vergadering en deelt mede, dat de volgende
vergadering wegens den beperkten treinenloop (]e^ namiddags om 3 uur
gehouden zal worden.

De Heer H. C. Redeke lioudt een voordracht over nanno- of cen-
trifuge-plan kt on. Hij Ijegint met er op te wijzen, dat voor betrek-
kelijk korten tijd plankton uitsluitend met lijnmazige netten verzameld
werd. Het lijnste weefsel, dat daarvooi- gebruikt kan worden, is buil-
gaas N". 25 (oud N*^. 20), waarvan de Jiiaaswijdte ongeveer 50 (j. be-
<li'aagt.

De groote massa der kleinere pelagische oiganismen, Bakteriën, Pro-
tophyten en Protozoen, ontsnapt door deze mazen ; die allerkleinste
planktonten kunnen dus niet met netten worden verzameld. Daar zij
een groote rol spelen vooral als voedsel voor grootere organismen (Ap-
pendicularia !) en vaak een aanzienlijk bestanddeel van het plankton
vormen (Kofoid, Loh.mann), werd naai' middelen omgezien om ook dit
allerkleinste jtlankton , door Lohmann ,,ii!inii(iplankton" genoemd, te
vangen.

Filters van verschillende stollen (papiei-, zijde, leer, porcelein, zand)
hebben het Ijezwaai', dat van de teere oi'ganismen dikwijls slechts een
onherken))are massa overblijft. Een voortreffelijk instrument om dit
nannoplankton te verzamelen is evenwel de centrifuge. Men noemt het
nannoplankton dan ook vaak ,.centi'ifuge-|>lankton in tegenstelling met
het grovere ,,netplankton".

Spreker demonstreert een kleine centrifuge, zooals die aan het Rijks-
instituut voor P)i()l()gisch Vissclierijonderzoek in gebruik is en vestigt er
in liet bijzonder de aandacht op, dat deze methode zich ook tot quanti-
tatieve onderzoekingen leent.

lx

Voorts bespreekt hij aan de hand van eenige afbeeldingen de voor-
naamste bestanddeelen van liet zoetwater-nannoplankton van ons land
(Diatomeen, Peridineen en andere Flagellaten, Chlorophyceen) en staat
meer in het bijzonder stil bij het voorkomen van een zeer verspreide en
als voedsel voor onze planktonton uiterst belangrijke Clirysomonadine:
Chrysococcus mfescens Klebs.

e»

Mejutl'rouw M. van Herwerden doet een mededeeling naar aanleiding
van een achtjarig onderzoek bij Daphnia pvlex. — Spreekster
heeft sedert Januai"i'i9i0 Daphnia pulex in het laboratorium gekweekt
met het doel nader inzicht te krijgen in het wezen der cyclische
voortplanting. Van een Dajihriia., Januai'i 1910 geïsoleerd, is tot
heden het nageslacht, waarvan een stamlijst w(M-d bijgehouden, in leven.
Door een eenvoudige nomenclatuur kan men van elke JJapluiia hun
plaats in de stamlijst aanwijzen. De kweekproeven werden zoowel bij
kamertemperatuur, als in de kelder en op een broedstoof (watertempe-
ratuur l!2° — 18°) verriclit. De snelheid der embryonale ontwikkeling bleek
tusschen 10 en 20° in grove trekken de wet van van 't Hoff te volgen
(dit werd in een afzondei'lijke pi-oefreeks bij constante watertemperatuur
aangetoond).

Het onderzochte ras van Daphnia pa Ier, dat in de natuur monocy-
clisch was, bleef deze monocyclie ook tijdens de kweekproeven behouden
gedurende al deze jaren; de sexualiteit was het ééne jaar sterker uitge-
sproken dan het andere jaar, zonder dat een vermindering in den looji
der jaren viel waar te nemen. Meestal neemt de sexualiteit, welke in
October begint, af tegen Februari om daarna nog een tM'eede geringere
verliet'fing te vertoonen. Terwijl in de natuur in den winter alleen de
ephippiaaleieren overblijven, ziet men in het laboratorium een deel dei'
Daphh'ia's zich ])arthenogenetisch verdei' ontwikkelen. Zoo werd b.v.
van Januari 1910 tot Februari 191(3 een reeks van parthenogenetische
generaties in het leven gehouden, zondei' inschakeling van een ephip-
pium. 0})iiierkeiijk is het, dat eiken herfst gelijktijdig in kamer-, kelder-
en stoofculturen bij een deel der Dapliiiia's de geslachtelijke voortplan-
ting begint, en wel bij dieren met erfelijk zeer uiteenloo-
pend e formule; zoowel bij eerste als latere broedsels, bij generaties-
lang geïsoleerde als Ijij gezamenlijk gehouden exemplaren.

In tal van jjioeven werd getracht kunstmatig invloed op het ontstaan
der gametogenesis uit te oefenen, fliiu'bij bleek in overeenstemming met
VVoltereck's resultaten, dat plotselinge afkoeling van de eieren in het
laatste stadium der rijping in staat is (J' exemplaren te doen ontstaan,
hetgeen echter alleen gelukt in een tijdjtei'k van labiel evenwicht der
geslachtelijke en ongeslachtelijke neigingen. Hierbij kwam ook het eigen-
aardige verschijsel der pi'aeinductie voor den dag, namelijk een sexueele
ditferentiatie der kleinkinderen van een wijfje, dat 24 uur tijdens rijp-
heid der eiei'en in de ijskast had vertoefd. Op de hoogtegolf der par-
thenogenetische phase zijn dergelijke proeven zonder resultaat. Bestra-
ling met ultraviolet licht of met radium bleek geen invloed te hebben
op het geslacht. Ook met gewijzigde voeding of toevoeging van verschil-
lende chemicalia bij het slootwater werd geen resultaat verkregen. In
het laboratorium blijft dus onder veranderde levensomstandigheden de
cyclische voortplanting bestaan, ook als er geen gevaar voor het uit-
sterven der parthenogenetische dieren meer dreigt. Is dit rhytmisch
gebeuren erfelijk vastgelegd of zijn het invloeden van den herfst, die

X

aan onze waarneming ontsnappen, welke ook in liet laboratorium werk-
zaam blijven ?

Het ras van Ikiphnia jmlex, dat gedurende deze jaren in cultuur is
gehouden, vertoont volstrekt geen ontaarding. Tijdelijke depressies worden
door toevoeging van sporen van cvankalium, manganocldoride of andere
chemicalia, ook wel door tijdelijke voeding met gist opgeheven. De nei-
ging tot variabiliteit is zeer groot, hetgeen reeds na de proeven van
WoLTERECK te verwachten was. Als eenige morphologische verandering
werd het verdwijnen der chitinetandjes genoteerd, welke gedurende het
eerste cultuurjaar bij vele pasgeboi'en Daplmin's aan de dorsaalzijde der
schaal aanwezig waren.

De Heer C. Ph. Sluiter doet de volgende mededeeling over de tril-
h aargroeve van eenige A s c i d i e n.

Het is sedert de nauwkeurige onderzoekingen van Cii. Julin en Ed.
V. Beneden uit het jaar 1881 algemeen bekend, hoewel reeds in 1876
liet eerst door Ussow beschreven, dat bij Phallusia mammülctta de
zoogenaamde ,,Neuraalklier", door de genoemde auteurs toenmaals ,,ap-
pareil hypophysaire" genoemd, bij nog jonge dieren uitsluitend door
middel van een enkelvoudig primair kanaal uitmondt in de bekende
trilhaargroeve, openende in het voorste gedeelte van den kieuwzak;
maar, dat bij oudere exemplaren secundaire vertakkingen aan liet pri-
maire kanaal optreden, die naar de peribranchiale ruimte toegroeien en
daarin ten slotte met secundaire kleine trechtei'vormige openingen uit-
monden. Tegelijk neemt de omvang der neuraalklier geleidelijk af'.
Later is hetzelfde verschijnsel bij eenige andere groote PltaUusia-soor-
ten gevonden, terwijl gewoonlijk, zoo niet altijd, daarmede gepaard gaat,
dat de trilhaargroeve zelve kleiner wordt. Bij een opvallend groote
Pliallusia-soort, die ik binnenkort onder den naam van PJi. julinea n.
sp. zal beschrijven, vond ik nu het extreme geval van dezen toestand.
De trilhaargroeve was bij dit dier volkomen verdwenen niet alleen, maar
de voorste punt van de dorsaalplooi was naar voren gegroeid, zoodat de
coronaalzoom hier zelfs zeer smal werd. De neuraalklier zelf was geheel
rudimentair geworden, maar talrijke secundaire kanaaltjes hadden zich
uit den primairen gang ontwikkeld en monden in de peribranchiale
ruimte uit. Wij hebben dus hier wel een uiterste geval voor ons van
de waarschijnlijk niet slechts morphologische, maar ook physiologische
omvorming van deze neuraalklier.

Nog op een tweede eigenaardigheid in l)etrekking tot de trilhaar-
groeve wil ik wijzen. De oorspronkelijke vorm van deze groeve of int-
monding van het kanaal der neuraalklier is wel ongeveer cirkelrond,
zooals dat bij verschillende, meer oorsprordvelijke vormen gevonden wordt.
Nu blijkt deze eenvoudige vorm bij kleine dieren, met name bijvoor-
beeld bij alle mij bekende kolonievormende soorten te blijven bestaan,
onverschillig tot welke systematische groep deze kolonievormende dieren
behooren. Bij grootere vormen, zoo bij de meeste alleen levende Asci-
dien, wordt de vorm meer gecompliceei'd, maar laat zich toch veelal tot
den typischen hoefijzervorm terugbrengen. Nu vond ik, dat bij een buiten-
gewoon groote Poiycilor-soort, waarbij de afzonderlijke dieren de voor
kolonievormende Ascidien enorme grootte van i'/j f-M. bereiken (waar-
om ik dezen vorm dan ook weldra als Polycitor f/if/antens zal beschrijven),
de trilhaargroeve niet meer de typische ronde of ovale gedaante bezit,
maar den gewonen hoefijzervorm. die zoo veelvuldig bij de alleen levende

A.scidieu «gevonden wordt. Men wordt liierdoor wel versterkt iii de laee-
iiiiig, dat de hoelijzervormige instulping der opening afhankelijk is van
de grootte der individuen.

De Heer G. B-omijn deelt mede, dat de voorloopige excursie voor het
Maasonderzoek dezen zomer is gehouden.

Bij het onderzoek der Najaden op parasitische mijten, welke daarbij
niet werden gevonden, had hij in een dier, dat door Mej. Scholtkn als
Unio tionidus is gedetermineerd en dat aan het eene einde blijkbaai'
gekwetst geweest was, eenige parelen in het weefsel van den mantel
gevonden. Hoewel ze slechts klein en voor het meerendeel slecht ge-
vormd zijn, aclit hij het voorkomen tocli zeldzaam genoeg om de vondst
hier te demonstreeren.

De Heer L. Peeters doet een mededeeling over het voorkomen van
(MrdyJophora hivuMr'oi en EusponrjiUa Jacustris in de Zuid-HoUandsclie
meren (cf. p. xvii).

XII

WETENSCHAPPELIJKE VERGADERING.

Amsterdam. Kleine Restauratiezaal van het K. Z. Genootschap „Natura
Artis Magistra". 30 November 1918. 's Namiddags drie uur.

Aanwezig de Heereii: Sluiter (Voorzitter), Baas Becking, de Beau-
fort, Begemann, van Bemmelen, Bolsius, Büsciima, de Burlet, de
BussY, Dammer.man, Droügleever Fortuyn, Druyvesteyn, G. L. Funke,
VAN Goor, Heimans, Ihle, Jordan, vam Kampen, Kerbert, de Lange,

LOMAN, DE MeIJERE, VAM OORDT, PeETERS, ReDEKE, RoMIJN, A. M. H.

SCIIEPMAN , ScniERREEK , SciIUUHMANS StEKIIOVEN , VAN SeRVELLEN ,

Stracke, van Wijhe; en de Dames: Bastert, van Bentiiem Jutting,
Berkhout, Boterhoven de Haan, Droogleever Fortuyn-van Leyden,
Feutkamp, Fortuyn Droogueever, van Hersverden, van 't Hoff, Jon-
GES, Knoop, Lens, de Lint, Löiinis, Sciiijesma, Sciiolten, de Vos,
Vorstman, Wibaüt-Isebree Moens.

Als gasten de Heeren : Dr. H, G. Ringei-ing, J. Hoike.

De Voorzitter opent de vergadering en deelt mede, dat het Ministerie
van Landbouw, Nijverheid en Handel zoo welwillend is /'ISüO te be-
talen als 'il)ijdi'age in de kosten voor <le aanleg van elektriscli licht in
het Zoölogiscli Station. De Vereeniging is in staat de i^est der kosten
uit haar gewone middelen te betalen.

Daarna krijgt de Heer J. F. van Bemmelen liet woord om een mede-
deeling te doen over het k 1 e u i' e n ]> a t r o o n der S p h i n g i d e n en
zijn bete eken is voor de systematiek.

Onder de in Nedei'land voorkomende Pijlstaai'tvlinders of Sphingiden
zijn de Gehakkelde en de Pauwoogjdjlstaart (Snwr'ntlliKs jJOp'di en
oceUatus) twee nauwverwante vormen, niettegenstaande het in 't oog-
loopende verschil in teekening op de bovenzijde hunnei' vleugels. Die
vei'wantschap ])lijkt uit de groote gelijkenis tusschen liunne rupsen, die
zich daarbij ook met na-verwante plantensoorten : populier en wilg, voeden
Verder uit de groote overeenkomst der vleugelteekening aan de onder-
zijde, maar zeker wel het allermeest nit liet feit, dat de twee soorten
met elkaar vruchtbaar zijn, en bastaarden opleveren, die zelf ook nog
weer tot voortplanting geschikt zijn. Het is mij dan ook onbegrijpelijk,
dat de systematici het noodig hehben gevonden popidi uit net van ouds
bekende geslacht yïiiicnnUtKn te vei'wijderen en tot den vertegenwoordiger
van een ander geslacht A'iiioi'pJta te maken.

Wat nii die vleugelteekening betreft, beantwoordt popuU in hooge
mate aan de eisclien. die ik meende te mogen opstellen als kenmerken

XIIl

voor een primitief patroon van teekening, t. w. overeenkomst tussclien
vóór- en achtervleugel en tusschen boven- en onderkant, berustende op
het bezit van een eenvoudig patroon, gevormd door een motief van
teekening, dat over de geheele vleugeloppervlakte hetzelfde blijft en
zich streng houdt aan de scheidingslijnen gevormd door de vleugeladeren.
Dit motief bestaat bij jiopuli uit tusschenadervlekjes van meerendeels
convex-concave gedaante (de convexiteit naar buiten gekeerd), die zoo
legelmatig zijn gerangschikt, dat zij zich scharen tot overdwars over
den vleugel verloopende donkere handlijnen. Ofschoon met al deze
liinen even duidelijk, regelmatig en volledig zijn, kan men toch met
oToote mate van waarschijnlijkheid beweren, dat er zeven hoofdlijnen
zijn, en dat de voornaamste harer wederom begeleid worden door
minder donkere en scherpe vlekkenreeksen, zoodat het aantal dwars-
banden, wanneer men niet op diepte en scherpte van vlekteekemng let,
noo' liooger zou kunnen gesteld worden. Op de bovenzijde van den ach-
tervleugel van popuU wordt het gelieele wortelveld ingenomen door een
steenroode tint, die voornamelijk teweeggebraclit wordt door liaarvormige
schubben, en die blijkbaar de oorspronkelijke teekening overschaduwt
en wegvaagt. Aan de onderzijde van den achtervleugel, waar die roode
beharing ontbreekt, is dan ook de teekening duidelijker en vollediger,
terwijl omgekeerd het wortelveld van den vooi'vleugel aan die zijde door
een grijze beharing is overschaduwd.

Bij ocellahiü daarentegen is de tegenstelling tusschen voor- en achter-
vleugel aan den bovenkant zeer in 't oogloopend, en wijkt vooral de
aclitervleugel van de bovengestelde eischen voor een oorspronkelijke tee-
kening sterk af. Op den bijna homogenen rozerooden grond, die onge-
veer de gelieele ziclit1)are oppervlakte van den aclitervleugel inneemt,
staat n.l. een groote, sclierp met donkerzwart gecontoureerde oogvlek, die
een donkere pupil op een smalle lichtblauwe iris vertoont.

De voorvleugel daarentegen is gemarraoreerd met donkere vlekken
van verschillenden omvang, vormen intensiteit op lichtbiuingrijzen grond.

Deze teekening bezit een dubbele biologische beteekenis: in de eerste
plaats vormt zij een beschermingsmiddel voor het dier, wanneer het
overdag zit te slapen te midden der wilgentakjes. Dan overdekken de
vóór- (ïe achtervleugels, met uitzondering van het voorste gedeelte dezer
laatste, dat bij het vliegen juist onder de voorvleugels verscholen blijft
evenals bij andere vlinders, en dan ook bij de meeste hunner van teeke-
ning verstoken is.

Hier daarentegen is het geteekend met dezelfde geschulpte lijnen en
in overeenkomstige tinten als de voorvleugels, en vormt daardoor als 't
ware een voortzetting van deze naar voren, waardoor de gedaante van
een ineengekiinkeld blad met een middennerf en zijnerven nog treflen-
der is nagebootst. Wanneer ecliter het dier in zijn slaap wordt ge-
stoord, laat het de voorvleugels in voorwaartsche richting zakken, zoo-
dat het achterste deel der achtervleugels zichtbaar wordt, en twee groote
zwartgerande lichtblauwe irissen rondom een wijde zwarte pupil uit een
roze oogveld van onder zware donkere wenkbrauwen (de vlekken langs
den achterrand der voorvleugels) den belager schijnen aan te staren,
die, zooals ])roeven bewezen hebben, daardoor heftig verschrikt wordt.

Nu laat zich gemakkelijk aantoonen (zooals 'op overtuigende en namv-
keurige wijze is geschied" door J. Botke in zijn proefschrift: Les motits
primitifs du dessin des ailes des Lépidoptères et leur origine phylétique,
Groningen 1916, pag. 106), dat deze teekening der bovenzijde van oed-

M \-

/('/(^s als een secuiulaire wijziging mui die \aii [jopiill niag opgevat wor-
den, dat o, a. de oogvlekken der achtervleugels niet anders zijn dan de
achterste uiteinden der drie buitenste dwarsbanden, die bij pojnili zich
uitstrekken langs den gelieelen buitenrand der l)eide vleugels, dat verdei'
het roze oogveld slechts een iets grootere uitbreiding in distale richting
van het roede vv'ortelveld van dezen laatste vormt, en dat op het voor-
stuk der achtervleugels de oorspronkelijke teekening van gekartelde
dwarslijnen evenzeei', zij het niet in zoo hooge mate, is behouden ge-
bleven als bij pojndi, wat in verband staat met het feit, dat in den
ruststand oceUatus hare achtervleugels niet zóóvei" voor de voorvleugels
uitstrekt als popiUi. Ook de vergelijking met verwante soorten levert
bewijzen voor dit verband tusschen de achtervleugelteekening der beide
soorten. Bij Smennthvs kinderinanni b.v., die overigens in teekening
Ijijna volledig met ocellattif^ overeenkomt, is de vlek aan den acliterhoek
van den achtervleugel veel minder oog vorm ig dan bij deze laatste, daai'
zij uit di'ie ongeveer evenwijdige bandstukken bestaat, en wordt, gelijk
BüTKE opmerkt, de iris slechts door twee niet met elkaar samenljan-
gende lichte streepjes vertegenwoordigd. Bij Sm. coecus daarentegen nadert
de oogvlek in gedaante en grootte tot die van oceUati(><, maar vertoont
de gemai'moreerde teekening van den voorvleugel grooter overeenkomst
met die van poptdi, daar het donkere middenveld evenals bij deze laatste
ongebroken van vóór- tot acliterrand doorloopt en niet als bij oceUaiiis
en kindermanni in een vciói'- en achterstuk is dooi* midden gesnoerd.

Het verschil tussclien de bovenzijde van vó(ir- en achtervleugel bij
oceUatus blijkt dus te berusten op wijziging in geheel verschillenden zin
van één en hetzelfde })atroon, dat dan ook aan de ttnderzijde bijna vol-
ledig bewaard is, evenals aan boven- en onderzijde beide van popidi.

Men zou geneigd kunnen zijn, hieruit af te leiden, dat wij bij popidi
te doen hebben met een teekening, die als de oorspronkelijke van het
genus Smerinthus mocht opgevat worden, en bij de bovenzijde van ocel-
latus met eene, waaraan slechts specifieke waarde moclit toegekend worden.

Dat deze laatste conclusie te eng genomen zou zijn, blijkt reeds uit
de bovengenoemde gevallen van coecn(s en kindennanni, maar nog over-
tuigender uit de vergelijking met minder na vervvante vormen, zooals
b.v. iUiae. Hier is op den bovenkant der voorvleugels klaarblijkelijk
hetzelfde patroon aanwezig als bij occIJalus, maar in geheel andere uit-
voering, zoowel wat lijnen als wat kleuren betreft. Op den achter-
vleugel is het patroon grootendeels verdwenen, maar wat er van over
is, vertoont naar den achterhoek der vleugels toe een sterke toeneming
van zwarte kleurstofophooping, die nabij den hoek aanzwelt tot een
donkere bandvlek. Dit is dus tot zekere hoogte aanduiding in de richting
van oogvlekvorming aan dien vleugelhoek.

Hoogst merkwaardig lijkt mij de teekening van tartarinoviï, die als
't ware een ovei'gang tusschen oceUatus en tiUae vormt, daar het patroon
van den voorvleugel meer op dat van de laatste, dat van den achtervleugel
meer op dat van de eerste lijkt, o. a. door de roze verkleuring, ofschoon
van de oogvlek slechts een vage aanduiding, door ophooping van zwart
pigment, aanwezig is.

Aan den onderkant komen al de genoemde vormen sterk met elkaar
overeen, en is het patroon 'van vóór- en achtervleugel bijna volledig aan
elkaar gelijk. Het doet zich n.l. voor als een vereenvoudigde en ver-
armde lijnenteekening, waarvan het volledige en hoog gedifferentieerde
prototype op den bovenkant van jjopaU staat uitgewerkt.

NV

Langs (lezen we;^ van vergelijking met aiiileie, zuuwel nader als vei-
wijderdei' verwante soorten, kan men ■voor ieder dillerentieel kenmerk
der vleugelteekening van ocdiaius aantoonen, dat het niet speciliek eigen
aan en onderscheidend voor die soort is. dorh aan een reeks van vlinder-
VTjrmen gemeen. Als soortelijk eigenaardig blijven ten slotte slechts de
kleine bijzonderheden der afzonderlijke bestanddeelen van de teekening
over: zooals l).v. de grootte en afgerondheid van de oogvlek, en liare
verplaatsing van den achterhoek des vleugelrands naar binnen. Even-
min als de eigenaardigheden, waardoor ocellalus zich vau jjoj^jh^j onder-
scheidt, mogen opgevat worden als soortskenmerken van eerstgenoemde,
gaat het aan om de kenmerken, waarin zij met populi overeenkomt,
zonder meer als generieke te l)esch(mwen. De verdeeling toch in zeven
hoofddwarsbailen , elk samengesteld nit tusschenadervlekken, en van
elkaar gescheiden door lichtere tnsschenrnimten. waarin rijen van min-
der in 't üogloopend gepigmenteei'de vlekken knnnen gelegen zijn, komt
niet sleclits in meerdere andere Sphingidengenera voor, maar schijnt ook
ten grondslag te liggen aan het klenrenpatroon van vei'scheidene andei'e
families van vlinders, ja wellicht aan dat van alle. Under andere kon
ik een dergelijk patroon gemakkelijk opsporen bij de fam.(ler ^4rc^/n/a^',
en blijkt Mej. A. F. Braun, geheel onafliankelijk van deze mijne opvat-
tingen, bij de analyse van het klenTenpatroon der Tineidenfamilie JA-
ihocoUeih tot een gelieel overeenkomstig patroon van zeven donkere
dwarsbanden te zijn gekomen.

In geen geval echter kan het ontstaan der eigenaardigheden van een
of andere vleugelteekening toegeschreven worden aan de beschermende
beteekenis, welke die teekening voor het dier bezit. Protectieve of ad-
vertatieve patronen vormen geen afzonderlijke categoiien van teekening,
zij dragen geen eigen karakter, maar zijn niets anders dan bijzonder
gespecialiseerde gevallen van het algemeene patroon, dat aan een geheele
groep van verwante soorten en geslachten eigen is. De bijzondere ge-
acheveerdheid, waardoor zij zich van de 't naast met hen overeenko-
mende onderscheiden, kan wel door natnurkenze belionden blijven, maar
nimmer er door teweeggebraclit zijn. Met de bewering, dat een of an-
der klenrenpatroon niet primitief, maar slechts een sympatliisclie, na-
bootsende teekening is, w^ordt dus een tegenstelling gemaakt tusschen
twee ongelijkwaardige zaken, die niet met elkaar in verband mogen
gebracht worden. Nabootsend of waarschuwend kan iedere teekening
werken, een oorspi'onkelijke evengoed als een secimdair gewijzigde. De
teekening der beide vleugelparen van populi bootst evengoed den vorm-
en de kleurschakeeringen van een dor blad na als die der voorvleugels
van ocellatiis, de steenroode overharing van het wortelveld harer achter-
vleugels heeft wellicht een dergelijke biologische beteekenis voor populi
als de paarsroode verkleuring bij oceJlatus, al ontbreekt in de eerste ook
de oogvlek, die er bij laatstgenoemde zoo sterk tegen afsteekt.

Hoezeer zulk een verkleuring, waaronder het oorspronkelijk patroon
schuil gaat, en waardoor het in vele gevallen geheel tot verdwijnen
wordt gebracht, als een secundaire wijziging verdient opgevat te worden,
zien W'ij onder de Sphingiden op een merkwaardige wijze ons voor oogen
gesteld door de Braziliaansche soort PJiohoi lahrusiac. Bij deze bestaat
tusschen vóór- en achtervleugel een niet minder schrille tegenstelling
dan bij Smeyinthus ocellatus, al draagt de achtervleugel van lahrKsiae ook
geen oogvlek. Op beide vleugelparen is het oorspronkelijk patroon sterk
gewijzigd, en wel in tegengestelden zin: op de voorvleugels is het groo-

XVI

tendeels vervaagd en vereenvoudigd door een bijna volledige veigi'oening,
die zich eveneens over de bovenzijde van kop, tliorax en abdomen uit-
streivt, op de achtervleugels daarentegen vertoont het een schijnbaar bonte
mengeling van geel, rood, blauw, groen en zwart. Toch kan 'men op beide
vleugels de sporen van het oorspronkelijke gemeenschappelijke patroon
gemakkelijk terugvinden, en ook waarnemen, dat het onderscheid tusschen
beide het normale, aan alle Sphingiden eigene karakter draagt, d. w. z. dat
vócir- en achtervleugels overeenkomen met de gelijknamige vleugels van
andere pijlstaartsoorten, zoowel in de daarop bewaardgebleven overblijfselen
der oorspronkelijke teekening, als in de manier, waarop deze gewijzigd is.

In laatstgenoemd opzicht vertoont echter de voorvleugel van labrn-
■■<iae één zeer opmerkelijke bijzonderheid: op het midden n.1. bevin-
den zich twee vierkante ])lekken, waar de groene grondkleur is ver-
vangen door een bruine, licht en donker gespikkelde, en op welke een
viertal gebogen zwarte streepjes staan, die geheel het karakter der con-
vex-concave staafjes van de /K>/*(i'//-teekening dragen. Men krijgt den
indruk, alsof in liet bijkans egaal-groene vleugelveld twee vensters zijn
opengelaten, waar doorheen een paar tragmenten van een geheel anders
gekleurden en geteekenden vleugel zichtltaar worden. Volgens mijne
overtuiging is dit ook werkelijk het geval, in zooverre als de beide
fragmenten in kleur en teekening beide een oorspronkelijker toestand
bewaard hebben dan de overige vleugelo])pei'vlakte. Op den achter-
vleugel is de dooreenmenging van gewijzigde en oorspronkelijk gebleven
partijen al even grillig; de gele, blauwe, roode en groene plekken zijn
door verkleuring, de zwarte daarentegen door ineensmelting van don-
kere vlekken ontstaan. Slechts nabij den acliterhoek zijn enkele sporen
van het oorsproidielijke jiatioon bewaard gebleven, in den vorm van
drie smalle onregelmatige bandstreepjes, die ongeveer overeenkomen met
de breedere en gelijkmatiger donkere banden van Snu'rinthKs coecus.

Aan de onderzijde bestaat de gewone toestand: vóói- en achtervleugel
in hoofdzaak aan elkaar gelijk, daar op beide vei'eeiivoudiging en re-
ductie van het oorsjtronkelijk ])atroou op overeenkomstige wijze heeft
plaatsgegrepen, n,l, door verkleuring van den vleugelwortel uit, in één
en dezelfde tint onder behoud van twee donkeider bandstrepen over 't
middenveld, en onder dillérentiatie van een buitenrandsveld,dat dooreen
zigzaglijn van de overige vleugelvlakte woi-dt afgegrensd.

Dit patroon der onderzijde werd zooals gezegd, in zijn hoofdkenmerken
teruggevonden niet alleen bij alle Sphingiden, maar ook bij de meer-
derheid dei' overige Nachtvlinderfamilies. Het mag dus niet eenvoudig
als een familiepatroon worden aangemerkt, maar bezit een veel verder
reikende beteekenis. Hetzelfde geldt voor de aan alle S})hingiden ge-
meenscliap])elijke hoofdtrekken van 't pati'oon dei' bovenzijde, ook deze
zijn niet tot de leden dier familie beperkt, maar worden evenzeer aan-
getroflen in verwante families zooals Lipariden, Bombyciden, Noctuiden,
Geometriden enz. M. i. ))estaat er geen rt^den om de overeenkomsten
binnen de perken van een genus of eene familie aan verwantschap, die
tusschen vertegenwoordigers van verschillende families aan paralelle
ontwikkeling (z.g. convergentie) toe te schrijven, veeleer zou ik ook deze
willen verklaren uit liet manifest-worden van aan beide families ge-
meenschajijielijke erfelijke teiidenzeii, wier pliyletische ouderdom voor
ieder kenme)'k afzonderlijk moet bepaald worden, maar in 't algemeen
gesproken, nieeslal onder zal blijken dan de families zelf, ja dikwijls dan
de oide of zelfs de klasse, waartoe die i'aniilies behooreii.

XVII

Mevrouw Wibaut-Isebree Moens deelt liet volgeiule mede:

Het resultaat van o jaar plankton-onderzoek van de A m-
sterdamsche grachten leert dat:

i. tengevoljie van het gevolgde spuisysteem de grachten een zeer
wisselende saliniteit liehben;

'2. er een min of meer markant verschil is tusschen de Cl-cijfers
\s zomers en 's winters. Deze zijn 's zomers door het vele ingelaten
/ u i d e r z e e - s p u i w a t e r hoog, en de brakwater- en marine-organismen
belieerschen dan plaatselijk het planktonbeeld; 's winters is het Cl-
gehalte veel lager door het overvloedige Amstelwater, wat nog grootere
armoe aan organismen meebrengt;

3. de planktonorganismeu Van Schinkel en Am stel ondergaan, zoo-
dra zij in de stadsgrachten komen, den invloed van een verzouting en
van een vervuiling. Men kan door reeksen van monsters, op denzelfden .
dag genomen op punten steeds meer naar 't centrum van de oude stad,
uitmaken, dat 'tmeerendeel der zoetwaterorganismen sterft;

4. de planktonorganismen van 't bij Zeeburg instroomende Zuider-
zeewater sterven voor 't meerendeel af, of lijden een kwijnend be-
staan; daar het Zuiderzeewater op ziciizelf reeds zeer wisselend van zout-
gehalte is en de erin voorkomende organismen eurylialien zijn, komt
het mij voor, dat hier de invloed der vei'vuiling zich doet gelden en
dat, wanneer, zooals nu in de nieuwe stad (h)or de nieuwe rioleering,
de toestand verbetert, de Zuiderzeeplanktonten het ook in de binnen-
stad uit zullen liouden en daadwerkelijk tot de reiniging van het stads-
water zullen medewerken:

5. uit de gezameidijke analysen bleek, dat het gi'achtennet te ver-
deden is in een aantal gebieden, allen min of meer met een eigen plank-
tonbeeld: naar 't oosten en noorden ovei'lieerschen de brakwatervormen;
naai" 't zuiden en westen de zoetwaterorganismen. In de binnenstad
komen dan ook in de meest vervuilde gedeelten organi-smen voor, die
ik gi'achttypen zou willen noemen: niesopolysai>robe brakwater-orga-
nismen, die autochthoon zijn en zich saliniteitswasseling ne vervuiling
ten spijt sterk voortplanten.

Als verschillende gebieden zijn te onderscheiden :

I. Yan Lennepkwartier, Kostvei'lorenvaart en Nassaukade.
IL Jordaan tot en met Brouwersgiacht.

III. Gmchtennet ten westen van den Amstel.

IV. Binnen-Amstel, Rokin. Burgwallen, Singel.

V. Markengracht, Houtkoopersburgwal, Oost-Indische kade enz.
VI. Funenkade, Entrepót-dok, gracliten ten oosten van den Amstel.
VII. Amstel^ Stadliouderskade, Mauritskade.
VIII. Het I.], Open Haven bij het Centraal-Station, Oostei'dok, Dijks-

gracht.
Over de namen der planktonsoorten zal eldeis een mededeeling ge-
daan worden.

De Heer L. Peeters bespreekt het voorkomen van Cordylojihora la-
cKstiis en Eiisponc/illa lacvstris in de ZuidhoUandsche meren,
den W^steinder Plas meegerekend. Naar aanleiding van de bespre-
kingen over bijdragen voor de Fauna van Nederland, op de zomerver-
gadering Van 1905 te Leiden, vatte spreker het plan op een onderzoek
in te stellen naar de Fauna van bovengenoemde meren. Met een motor-
bootje kon hij van Katwijk a/d Rijn uit, kanalen en meren bezoeken. Een

N \- 1 1 1

der eerste dieren, welke gevonden werden, was (lordylupliuni^ in d
nabijheid der binnensluis te Katwijk a/Zee. Daarna werd zij ook overa^
gevonden in de kanalen en den Rijn ten noorden van Leiden en evenl
zoo in de meren. Vooral in den Westeinder Plas was zij sterk ver-
tegenwoordigd. In 19U7 verliet spreker Katwijk en zoo werd hem ee -
voortzetting van het onderzoek onmogelijk. Dit vertrek was ook dn
reden, waarom toen het zoutgehalte van het water niet onderzoche
werd. Volgens PI van Beneden (vgl. P'aiin. Aanteekeningen door Drt
Kerbkrt in: De Levende Natuur, 1918, bl. 75) is het water in de dok.
ken van Londen zoet, omdat het niet zout smaakt en ei" in voorkgmen-
de zo et water spons Ei(S[>(nu/iUa lacvslrifi en zoetwaterplanten als
lA'mrtü. Maar dan zoti ook het watei' in de kanalen en meren als zoet
te beschouwen zijn, omdat er behalve in den Westeinder Plas gevonden
worden Euspcnif/illa, Epliijdatia en tal van zoetwaterplanten. Euxpon-
f/illa groeit in liet Braassenierraeer in prachtexemplaren, maar in het
Norremeer b.v. alleen als overtrek van steenen. In het eerstgenoemde
meer leven polyp en spons vreedzaam liijeen : op de sponsboompjes
vindt men tal van polyijeiikolonies.

Thans is spreker er in geslaagd water te onderzoeken uit het ,, Addi-
tioneelkanaal" bij Katwijk a/d Rijn, uit de Kager- en Braassemermeren
en den Westeinder Plas. Van den Heer Dr. P. Aug. Drikssen, van de
Leidsche Katoenmaatschappij, wien hij hier openlijk dank zegt voor zijn
groote hulpvaardigheid, ontving spreker de geleidingsgetallen ') van het
water uit den Rijn, de kanalen en de meren. Deze getallen werden
met den z.g.n. .,Dionic"-Meter op velschillende tijden bepaald; zoo b.v.
tweemalen met een maand tusschenruimte in 1914; één keer in Oc-
tol)er '1916 en ook nu van een paar monsters water uit kanaal en
meren. Uit die getallen blijkt, dat het geleidingsvermogen en dus ook
het zoutgehalte van het water aan groote scliommelingen onderhevig is.
Afgeleid volgens Mohr en uit de geleidingsgetallen werd als laagste Na
Cl-gehalte gevonden 0,015 *'/q bij liet begin van het Braassemermeer,
juist daar, waar de Z(joeven vermelde prachtexemplaren groeien van
Ei(spongiUa. Verderop naai' de ringvaart toe wordt liet zoutgehalte
grooter en de spons kleiner en kleiner. In de Kagermeren is het Na
Cl-gehalte op het oogenblik. in November, 0,02 "Z,,, in 191(i volgens de
geleidingsgetallen bijna 0,00 "z^, in den Westeinder Plas 0,03 "/^ (dit
laatste zoowel volgens geleidingsgetal als volgens titratie); in het Addi-
tioneelkanaal te Katwijk a/d Rijn is het OjOlS^/^, het geleidingsgetal
489, terwijl hiervoor in 1910 als laagste waarde 9632 gevonden werd.
De gevolgtrekking is dus, dat liet water nergens als zoet beschouwd
kan worden, daar als Na Cl-gehalte van zoetw-ater geldt 0,00470 1 en
dat de planten en dieren, willen ze blijven leven, een sterk aanpassings-
vermogen noodig hebben. De bewijzen van E. van Beneden kunnen
dus niet aanvaard worden en de stelling van Dr. Kerbert (1. e.) : voor
Nederland is nog niet uitgemaakt, of Cordylophora in stilstaande zoete
wateren voorkomt, staat nog.

Wel is volgens spreker de verklaring gevonden, waarom Euspongüla
in de Kagermeren slechts als overtrek van steenen voorkomt: het hooge
zoutgehalte moet er voor aansprakelijk gesteld worden, waarvoor het
ge"drag van de spons in het Braassemermeer pleit. Ook de grootere tal-

i) Uitgedrukt in reciproke Megohms.

XIX

rijkheid van ConlyJopJtora in den Westeinder Plas en de geringere in
liet Braassemermeer behoeft geen verdere verklaring. Waarom Enspon-
f/ilJa in het geheel niet in den Westeinder Plas gevonden werd, eischt
verder onderzoek; volgens spreker kan de soms zeer sterke troebelheid
van het water er mede oorzaak van zijn. Na dit onderzoek vindt spre-
ker het zeer twijfelachtig, of nog als vindplaats voor Cordylophora in
zoet water geliandhaafd mogen worden de dokken van Londen en liet
kanaal bij Ostende (zie: De Levende Natuur, bl. 75); het bevestigd zijn
in het laatste geval op Dreyssena polymorpha is hem geen bewijs, even-
min als dit de eierkokons zijn van (Jrirononnis, waarvan er in den
W^steinder Plas een G-tal gevonden werden op een takje van 4 d.M.
lang, dicht bezet met Cordylophora.

Wegens te vergevorderd uur worden de aangekondigde voordrachten
van de Heeren de Lange en Jordan tot de volgende vergadering uit-
gesteld.

XX

ÏTAAMLIJST ')

VAN DE EERELEDEN, BEGUNSTIGERS, AANDEELHOUDERS, CORRKSPON-
DEERENDE EN GEWONE LEDEN

DEE

op 1 Januari '1919.

Kerel eden

De Heer Franz Eilhard Schulze, hoooleeraar, Berlijn, 1908.
» » Yves Delage, hoogleeraar, Parijs, 1908.

Gegunstigers

De Heer C. H. van Dam, voorzitter van het bestuur der Diergaarde, Koningin

Enima-plein, Rotterdam, 1885.
Mevrouw J. M. C. Oudemans— Schober, Huize „Srhoveuhorst", Putten ( Veluwe),
1897.
» Dr. A. Weber — van Bosse, Huize „ïlerbeek". Eerbeek, 1897.

Begunstigers, die jaarlijks bijdragen geven voor het Zoologisch Station

De Heer Dr. H. J. van Ankuni, oud-hoogleeraar, Zeist, 1878.

» » Dr. J. G. de Man, lerseke, 1878.

» » Dr. C. A. Pekelharing, hoogleeraar, Utrecht, 1892.

» » Dr. Max Weber, buitengewoon lioogleeraar, Eerbeek, 1890.
Het K. Z. Genootschap „Natura Artis Magistra", Amsterdam, 1878.

1) De Secretaris verzoekt dringend aan hen, wier namen, betrekkingen of woonplaatsen
in (leze lijst niet juist zijn aangegeven, of verandering ondergaan, hem daarvan eene ver-
beterde opgave te doen toekomen.

De
De

Erve
Heer

»

»

»

»

»
De

»
Heer

»
De

Erve

De

Heer

»
De

»
Heer

»

»

»

»

XXI

A.andeelhouders in de leeningen, gesloten voor den bouw (1889) en voor de
vergrooting (1894) van het Zoölogisch Station 'j

De Heer Dr. H. J. van Ankiim, oud-lioogleernar, Zeist., N". 1 (1889),

N». 14 (1894).
i van den Heer Dr. D. Bierens de Haan, Leiden^ N" 5 (1889).

Prof. M. C. Dekhuyzen. Utrecht, No. 7 (1889).

Jhr. Dr. Ed. Everts, 'sGravenhage, N». 11 (1889).

Dr. A. P. N. Franchimont, hoogleeraar, Leiden, N". 7 (1894).

J. Hoek Jr., Kampen, N». 18 (1894).

Dr. R. Horst, Leiden, N». 15 (1889).

Dr. A. W. Kroon Jr., Leiden, N». 3 en 24 (1894). ,
1 van den Heer J. W. Lodeesen, Amsterdam, N". 18 (1889), adres

Prof. van Leeuwen, Hooge Rijndijk 11, Leiden.

Dr. K. Martin, hoogleeraar, Leiden, N». 19 (1894).

Dr. E. Mulder, oud-huogleeraai-, Utrecht, N». 2!2 (1889).

J. R. H. Neervooi't van de PoW, Rijscnherg {Utrecht), N'^. '20 {1SS9).

Jhr. Mr. J. .E. van Panhuys, 's Gravenhage, N". 17 (1894).

M. M. Schepman, BoscJi en Duin, N^. 28 (1889).
De Erven van den Heer Mr. L. Serrurier, Batavia, N". 33 (1889).
De Heer Ph. W. van der Sleyden, 's Gravenhage, N». 31 (1889).
De Erven van den Heer Mr. M. C. A'eiloren van Thernaat, „Schothorst"

bij Amersfoort, N». 9 (1894).

Correspoiideerende leden

De Heer A. Alcock, lioogleeraar, oud-directeur van het Indische Museum
te Calcutta, Belvédère nabij Dartford, Kent, 1902.
» » Dr. R. Blanchard, professeur a la Facult<'' de Médecine, 226 Boulevard

Saint-Gerniaiu, Parijs, 1884.
^) » E. van den Broeck, conservateur au Musée royal d'Hist. Nat., Place

de rindustrie 39, Brussel, 1877.
» » Adr. Dollfus, 35 Rue Pierre-Charron, Parijs, 1888.
)' » Dr. F. Heincke, Direktor der Biologischen Anstalt, Z:/eZ(/o?fmd, 1888.
» » W. Kobelt, Schicanheim bij Frank/brt a. M. 1877.
» » Dr. J. Mac Leod, hoogleei-aar, Gent, 1884.
Z. H. Albert, vorst van Monaco, 7 Cité du Retiro, Parijs, 1888.
De Heer J. Sparre Schneider, coiservator aan het Museum, ÏVomstr, Noor-
wegen, 1886.

Bestuur

C. Ph. Sluiter, Voorzitter, 1916—1922.

J. F. van Bemrnelen, Onder- Voorzitter, 1916 — 1922.

J. E. W. Ihle, Secretaris, 1918—1924.

L. F. de Beaufoi't, Pennhigmeester, 1914 — 1920.

H. C. Redeke, 1914—1920.

J. C. C. Loman, 1914—1920.

P. N. van Kampen, 1918—1924.

Comraissie van. Redactie voor liet Tijdschrifl

C. Ph. Sluiter, als Voorzitter der Vereeniging.

J. F. van Bemmelen, 1915—1921.

J. C. C. Loman, 1917—1923.

.1. E. W. Ihle, Secretaris, (1913) 1914—1919.

Zoölogisch Station te Helder (!N"ie u-wediep)

H. C. Redeke, Directeur, 1902.

1) Voor zooverre de aandeelen op 1 Januari 1919 niet uitgeloot waren.

xxii

Oewone leden ')

De Heer J. L. Addeas, biol. docts., assistent bij de zoölogie; Verlenende Hee-
reweg 5a, Gi-oningen, 1917. '^
•;• » » ür. II. J. van Ankum, oud-hoogleeraai-, Zeist, 1872
■■■■' » » S. A. Arendsen Hein, Emmalaan 17, Utrecht, 1907
» » Dr. W. H. Arisz, Emmalaan 25, Utrecht, 1909.
» » L. J. M. Baas Becking, biol. stud., Prinses Marielaan 4, Amers-
foort, 1917. '

Mejuffrouw a R Bakker, biol. cand.. Houtstraat 6, Leiden, 1916.

" dam 1 9n ^^*' ^^^'^*®"^^ ^'J ^^ physiologie, Oosteinde 24, Amster-
«De Heer Dr. l]. F. de Beaufort, Huize „de Treek", Leusden (U.), 1904.
Ac\ nr • ^l H. Begemann, Nieuwegracht 71, Utrecht, 19J8.
10 Mejuffrouw T A. Bekkering, Zwanestraal 20«, Groningen, 1914.

-Je Heer Dr J F. van Bemmelen, hoogleeraar, Zuiderpark 22, Gro7iingen, 1894.
Mejuffrouw W. S. v. Beuthem Jutting, biol. stud., Amsterdam, 1919.
» E. C. Bei-ghege, biol. cand., Rijnsburgerweg 6c, Leiden, 1918.
» L;- Berkhout, Archi medesstraat 25, 's Gravenhage, 1914.
15 » KM. Beucker Andrea?, Laan Copes 20, 's Gravenhage, 1911.

n tt" i; r ^^"^Sfl. Phil. stud., Zoeterwoudsche Singel 48^, Leiden, 1911.
• i>e lieer Ur. ,r. A. Bierens de Haan, zoölogisch assistent aan het Handels-
museum van het Koloniaal Instituut, Weteringschans 93, Amster-
dam, 1909.

» » F. E. Blaauw, Huize „Gooylust", 's Graveland, 1885.
» » Dr. J. Boeke, hoogleeraar, Utrecht, 1897.
20 J^ . » C. de Boer Jr., uitgever. Helder, 1911.

Mejuffrouw N.H.W. M. de Boer, biol. stud., Nassaulaan 64, i/aarZem, 1916.
■ » Dr. M.Boissevam, Huize „Boschlust", J5t7</ioven, 1898.

ue Heer Ur. J. Boldingh, assistent bij het Departement van Landbouw,
Nijverheid en Handel, Bnitenzorg, Java, 1903.
^' ^' S'''ff". ^^^^' hoogleeraar, Mauritskade 61, Amsterdam, 1896.
25,. » » H. üolsius, S. J., leeraar aan het Seminarium, Oudenbosch, 1893.
» » L). Bo ten, militair apotlieker, Potterstraat I. 76, Bergen op
Zoom, 1911. T y f

» » Dr. S. E Boursma, leei-aar aan de H. B. School, Weltevreden,
Batavia, 1898.

* » » H Boschma, biol. stud.. Ceintuurban n 236'i, .lms<e>Y/am (vacantie-

adres: Bons bij Sneek), 1915.
Mejulfrouw Tr. Boterhoven de Haan, Haagweg 107 G, Leiden, 1914.
.,0 ue lieer J. M. Bottemanne, hoofdinspecteur der Visscherijen, van Blanken-
burgstraat 41,' 's GrauewAa^e, 1893.
■•" » » Dr. P. J. van Breemen, Curacao, 1901.

» ') Dr. C. E. B. Bremekamp, leeraar aan de Artsenschool, Soerabaia,
Java, 1909. '

De N. V. Boekhandel en Drukkerij voorheen E. J. BriU, uitgever, Leiden, 1876.
ue Meer Dr A J. P. van den Broek, hoogleeraar, Admiraal van Ghentstraat.
Utrecht, 1906.
35 Mejuffrouw J. Brouwer, biol. stud., Bezuidenhout 393, 's Gravenhage, 1918.
Tl ri" n r; Bruijn, Schuytstraat 229, 's Gravenhage, 1906.

i'e lieer Dr. M. de Burlet, prosectoi- aan het Anatomisch Instituut.

Utrecht, 1904.
' *^ '^ g»*- ^^ P; de Bussy, directeur van de afd. Handelsmuseum van het
Koloniaal Instituut, Teniersstraat 5, Amsterdam, 1902.

1) De namen der abonnés van het Tijdschrift der Nederlandsche Dier-
Kundige Vereeniging zijn met een * gekenmerkt. De leden der Vereeuigine
ReSe'" ^°"''/'^-- Pei' ^^el op het Tijdschrift abonneeren bij den secretaris der

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XXI II

Dr. J. Büttikofer, directeur der Diergaarde, Rotterdam^ 1888.
40 » » Dr. C. P. Cohen Stuart, plantkundige bij het proefstation voor
thee, Buitenzorg, .Java 1909.
Dr. P. J. S. Cramer, Buitenzorg, Java, IQOS.

Dr. J. M. Croückewit, Roemer Yissoherstraat 7, Amsterdam, 1888.
Dr. K. W. Dammerman, Gi-aaf Florislaan 12, Biissum 1907.
A. B. van Deinse, leeraar aan het gymnasium en de H. B. School,
Diergaardelaan 60«, Rotterdam, 1908.
45* » » Dr. M. C. Dekhuyzen, hoogleeraar aan de Veeartsenijkundige
Hoogeschool, Biltstraat 109, Utrecht, 1880.
» » Dr. H. C. Delsman, assistent aan het Zoötomisch Laboratorium

te Leiden, Leidsche straatweg 5, Oegstgeest, 1909.
» h Dr. P. A. Dietz, prosector bij de anatomie, Leiden^ 1908.
» » Jan den Doop, Deli-Proefstation, Medan, Deli, 1917.
» » J. D. Dorgels, leeraar aan de R. H. B. S., Van Sytzamastraat 4,
Leeuwarden, 1917.
50* » » Dr. A. B. Droogleever Fortuyn, lector in de histologie, Leidsche
straatweg 64, Oegstgeest, 1906.
Mevrouw C. E. Droogleever Fortuyn — van Leyden, biol. doet», Leidsche

straatweg 64, Oegstgeest, 1911.
De Heer C. Druyvesteyn, biol. stud.. Kromme Nieuwegracht 74, [/irec/ii, 1917.
» » Dr. Eugène Dubois, hoogleeraar, Haarlem, 1896.
» » J. G. Dusser de Barenne, arts, Wilhelminapark 28a, f/frec/i^, 1918.
55 » » H. J. van Eekeren, leeraar aan het gymnasium en de H. B. School,
Groote Markt la, Schiedam, 1914.
» » Dr. J. E. G. van Emden, arts, Jan van Nassaustraat, 's Grat;en/iagre,
1887.

* » » P. J. van der Feen, biol. cand., Ganzenmarkt 23, Utrecht (vacantie-

adres: Domburg), 1916.
Mevrouw C. P. Feenstra— Sluiter, Batavia (Nic. Maesstraat 125, Amster-
dam), 1902.
Mejuffrouw A. J. Feltkamp, biol. stud., Honthorststraat 14, Amsterdam,
1916.
60 » J. Foftuyn Droogleever, Justus van Effenstraat 50&is, f/^rec/ïi, 1917.

A. W. Frederikse, arts, Zuidwolde (Dr.).

G. L. Funke, biol. stud., v. Eeghenstraat 81, Amsterdam, 1917.
H. C. Funke, Wageningen, 1914.

Dr. J. P. de Gaay Fortman, van Bleiswijkstraat 71 , 's Gravenhage, 1913.
65 » » Dr. A. E. van Giffen, conservator aan het Zoölogisch Laboratorium
te Groningen, Rijksstraatweg B 22, Haren bij Groningen, 1917.
» » Dr. A. C. J. van Goor, hoofdassistent aan het Rijksinstituut voor

biologisch Visscherijonderzoek, Parallelweg 17, Helder, 1915.
» » Hendrik Gouwentak, leeraar aan het Gymnasium, Lomanstraat 6,
Amsterdam, 1901.

* » "» Dr. H. W. de Graaf, conservator aan het Zoötomisch Laboratoi'ium,

Jan van Goyenkade, Leiden, 1880.
» » Dr. G. J. de Groot, leeraar aan de H. B. School, van Beverinck-
straat 155, 's Gravenhage, 1903.
70 Mejuffrouw A. van der Haas, biol. stud., Frankenslag 329, 's Gravenhage, 1915.
» M. van der Harst, Koudekerke (Walcheren), 1915.
De Heer Dr. H. W. Heinsius, leeraar aan de H. B. School, P. C. Hooftstraat
144, Amsterdam, 1889.
» 1) J. Heimans, biol. docts., Muidergracht 123, Amsterdam, 1912.
» » F. H. van Hengelaar, med. stud., Heerengracht 307, Amster-
dam, 1916.
75*Mejuffrouw Dr. M. van Herwerden, privaatdocent in de cytologie en assistente
bij de histologie. Parkstraat 47, Utrecht, 1908.
» J. Hingst, Huis te Lande, Vredenburgweg, Rijswijk (Z. H.), 1906.
» A. W. van 't Hoff, biol. stud., Amsterdam, 1919.

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XXIV

*De Heer H. R. Hoogenraad, leeraar aan de Rijks Kweekschool voor onder-
wijzers, Kromme Kerkstiaat 46, Deventer, 1904.
» » E. J. V. M. Hoogeveen, S. J., leeraar aan het Canisiuscollege, Nij-
megen, 1908.
80 » » D. van der Hoop, Mathenesserlaan 252, Rotterdaw, 1908.

» Dr. R. Horst, conservator aan het Rijks-Museum van Natuurlijke

Historie, Oude Vest 105, Leiden, 1872.
» Dr. C. J. van der Horst, 1^ assistent aan het Zoölogisch Laboratorium,

Aquariumgebouw, PI. Mui dergracht, Amsterdam, 1910.
» Dr. F. W. T. Hunger, van Eeghonstraat 52, Amsterdam, 1895.
* » » Dr. J. E. W. Ihle, hoogleeraar aan de Veeartsenijkundige Hoo-
geschool, Dillenburgstraat 13, Utrecht, 1904.
85 Mejuffrouw B. Immink, phil. cand., Groenhovenstraat 13, Leiden, 1911.
De Heer Dr. J. M. Janse, hoogleeraar, "Witte Singel 76, Leiden, 1902.
» >) Dr. H. Jordan, buitengewoon hoogleeraar, Frans Halsstraat 19,
Utrecht, 1914.
Mejuffrouw Greta A. Jonges, Zonrondom, v. Eedenstraat, Haarlem, 1916.
» M. C. Julius, biol. stud., Columbusstraat 276, 's Gravenhage,\Q\?>.
90*De Heer J. H. Jurriaanse, Schiekade W. Z. 75, Rotterdam, 1915.

Mejuffrouw B. Kaiser, assistente aan het Botan. Laboratorium, Groningen,

1916.
Mevrouw L. van Kampen-Zernike, Zoeterwoudsche Singel 81, Leiden, 1915.
■••"De Heer Dr. P. N. van Kampen, hoogleeraar, Zoeterwoudsche Singel 81,
Leiden, 1899.
» » Dr. J. R. Katz, Roemer Visserstraat 2, Amsterdam, 1902.
95* » » Dr. C. Kerbert, directeur van het Koninkl. Zool. Gen. „Natura
Artis Magistra", Amsterdam, 1877.
» » P. E. Keuchenius, Proefstation Besoeki, Djember, Java, 1908.
)> » C. J. van der Klaauw, biol. stud.. Geversstraat 16, Oe^s/yee^sf, 1917.
Mejuffrouw M. Knoop, Ruychaverstraat 6, Haarlem, 1919.
De Heer C. F. Koch, arts, res. off. van gezondheid 2Je kl., Haarlem, idll.
100 Mejuffrouw E. M. J. Koker, biol. cand., v. Baerlestraat, Amsterdam, 1915.
De Heer L. C. Kolff Jr., Huize sKolthoven", Epe (G.), 1914.
» » Dr. J. C. Koningsberger, voorzitter van den Raad van Indië,

Buitenzorg, Java, 1888.
» » W. J. C. Kooper, Stadhouderslaan 15, Leiden, 1917.
Mejuffrouw A. C. Kreulen, biol. stud., Burgemeester van Hasseltlaan 65,
Naarden, 1916.
105 De Heer P. Kruizinga, phil. docts., conservator bij de palaeontologie aan
de Technische Hoogeschool, Prins Hendriklaan 26, Bijswijk, 1909.
» » Dr. K. Kuiper Jr., Havelte (Dr.) 1911.
* » » Dr. Dan. de Lange Jr., directeur van het „Inst.itut international
d'embryologie", Gansstraat 62, Utrecht, 1902.
» » Dr. J. W. J^angelaan, oud-hoogieeraar, Vogelenzang bij Haarlem,
1897.
*Mejuffrouw A. Lens, leerares aan de H. B. School voor meisjes, Biltstraat
246is, Utrecht, 1901.
110*De Heer Dr. Th. W. van Lidth de Jeude, conservator aan het Rijks-Museum
van Natuurlijke Historie, Boommarkt, Leiden, 1877.
"-'■Mejuffrouw G. M. de Lint, assistente bij het Rijksinstituut voor biologisch
Visscherijonderzoek, Binnenhaven 86, Helder, 1S09.
» M. P. Löhnis, biol. cand., Jac. Obrechtstraat 75, Amsterdam,
1915.
■*De Heer Dr. J. C. C. Loman, van Baerlestraat 158, Amsterdam, 1881.
» >) Dr. J. P. Lotsy, secretaris van de Holl. Maatschappij van Weten-
schappen, Haarlem, 1900.
115 Mevrouw Agn. Lottgering, leerares aan de 1ste H.B. School, Graaf Floris-
straat 28a, Rotterdam (vacantieadres: Hengeloosche Straatweg,
Oldenzaal), 1914.

XXV

*De Heer Dr. J. G. de Man, Yerseke, 1872.

* » » J. C. V. d. Meer Mohr, 1913.

Mejuflrouw^J. H. H. van der Meer, assistente bij de palaeontologie aan de
Technische Hoogeschool, Koningin Emmakade 142, 's Gravenhaqe,
1917.
De Heer Dr. J. C. H. de Meijere, buitengewoon hoogleeraar, Sarphatistraat
76, Amsterdmn, 1890.
120 » » J. Metzelaar, biol. docts, rijksvisscherijleeraar, Linnaeusstraat 47,
Amsterdam, 1914.
Mevrouw M. F. W. A. Moerdijk — geb. Baronesse van Dedem van Driesberg,

Buitenzorg^ Java, 1913.
De Heer W. E. de Mol, biol. stud.. Transvaalstraat 112iii, ^ms^errfam, 1917.
» » Dr. J. W. Moll, buitengewoon hoogleeraar, Groningen^ 1890.
» » Dr. L. J. J. Muskens, arts, Anna Yondelstraat 6, Amsterdam, 1902.
125* » » Dr. H. F. Nierstrasz, hoogleeraar, Willem Barentzstraat 7, i/irec/ji,
1893.
» » P. Nieuwenhuijse, arts, Santpoort — Meerenberg, 1916.

* » » Wouter Nijholf, uitgever, 's Gravenhage, 1872.

* » » G. J. van Oordt, biol. docts., assistent bij de zoölogie en botanie

aan de Veeartsenijkundige Hoogeschool, Rembrandtlaan 6, Bilt-
hoven, 1913.
» » Dr. E. D. van Oort, directeur van het Rijks-Museum van Natuur-
lijke Historie, Zoeterwoudsche Singel, Leiden, 1897.
130 » » Dr. A. C. Oudemans, leeraar aan de H.B. School met5-j. cursus,
Boulevard Heuvelink 85, Arnhem, 1882.

* » » Dr. J. Th. Oudemans, huize „Schovenhorst", P?<fiew, Veluwe, 1885.
Mejuffrouw L. M. Paardekooper, biol. cand., Kaiserstraat 14, Leiden, 1918.

» D. J. Peck, assistente aan het geologisch en rnineralogisch
Laboratorium te Utrecht, Yilla „Varenne", Meerweg, Bussum,
1909.
De Heer Dr. L. Peeters, S. J., Hobbemakade 51, Amsterdam, 1905.
135* » » Dr. C. A. Pekelharing, oud-hoogleeraar. Maliestraat, Utrecht, \'èQO.
» » Dr. A. J. van Pesch Jr., Johaunes Verhulststraat 156, .Amsterdam,
1904.

* » B Mr. M. C. Piepers, oud-vice-president van het Hoog Gerechtshof

in N. I., Rijnstraat 3, 's Gravenhaqe, 1895.
Mejuffrouw M. Pijnacker Hordijk, Leidsche Straatweg 9, Oegstgeest, 1916.
*De Heer M. Pinkhof, biol. cand., Fi'anschelaan lic, Amsterdam, 1914.
140 Mejuffrouw Dr. C. M. L. Popta, concervatrice aan het Rijksmuseum van
Natuurlijke Historie, Leiden, 1919.
De Heer Dr. G. Postma, leeraar aan de H. B. School, Brink 41, Deventer,
1882.
» tt C. J. van Putten, arts, gep. officier van gezondheid Ie kl. O. I.

leger, Nassaustraat 2biB, Utrecht, 1883.
i> » Dr. F. H. Quix, lector aan de Rijks-Universiteit, Heerenstraat,
Utrecht, 1902.

* » » Dr. H. C. Redeke, directeur van het Rijksinstituut voor biologisch

Visscherijonderzoek, Helder, 1895.
145* » » Dr. J. van Rees, buitengewoon hoogleeraar, Hilversum, 1876.
Dr. E. Reinders, Willemstraat 40, 's Gravenhage, 1917.
H. W. Renkema, biol. cand., Weertsingel O. Z. 93, Utrecht, 1913.
A. Reyne, biol. docts., Landbouwproefstation, Paramaribo (adres
in Nederland: Kennemer Straatweg 180, Alkmaar)^ 1918.

* » » Dr. G. A. van Rijnberk, hoogleeraar, Ph^'siologisch Laboratorium,

Amsterdam, 1912.
150 » » Dr. W. E. Ringer, hoogleeraar. Stadhouderslaan 68, Z7<rec/i^, 1903.
» ï> Dr. J. Ritzema Bos, hoogleeraar aan de Landbouwkundige Hooge-
school, directeur v. h. Instituut voor Phytopathologie , Wage-
ningen, 1872.

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XXVI

*De Heer Dr. G. Romijn, Hintliamereinde, 's Hertog enbosch, 1916.
^Mejuffrouw Dr. P. J. de Rooy, Stadhouderskade 57, Amsterdam, 1904.

» Ch. L. Du Ry van Beest Holle, assistente aan het Zoötomisch

Laboratorium, Vreewijkstraat 11, Leiden.
:155 De Heer Dr. A. M. H. Schepman, directeur der N.V. J. B. Wolters' uit-
geversmaatschappij, Israëlsstraat 18, Groningen, 1912.

* » ->■> M. M. Schepman, Bosch en Duin (geni. Zeist). 1872.

"■■■ » » Dr. A. Schiei'beek, 2'ie Sweelinckstraat 147, 's Gravenhage, 1916.
Mejuffrouw K. Schijfsma, biol. stud., Plantsoen 35, Leiden, 1918.
*De Heer J. F. Schill, Laan Copes van Cattenburch 10, 's Gravenhage, 1877.
•160 » ), Dr. A. H. Schmidt, arts, Weistraat 130, Utrecht, 1893.

Mejuffrouw Joh. Scholten, Jacob Obrechtstraat 76, Amsterdam, 1909.
De Heer J. W. Schoor, biol. stud.. Nieuwe Mare 3, Leiden, 1916.
» » Dr. J. C. Schoute, hoogleeraar, Zuiderpark 2, Groningen., 1900.
)) » Dr. A. R. Schouten, leeraar H. B. School, Batavia, Java, 1902.
165 Mejuffrouw A. Schreuder., assistente bij de geologie en mineralogie, Valerius-
straat 251, Amsterdam, 1913.

Dr. J. H. Schuurmans Stekhoven, Jr., assistent bij de Zoölogie
aan het Instituut voor Tropenhygiene, Tilanusstraat 82i, Amster-
dam., 1914.

P. J. M. Schuyt, burgemeester van Wamel, 1903.
J. van Servellen, biol. stud., Bennebroekerweg, hoek Spieringweg,
Haarlemmermeer, 1915.

W. H. van Seters, biol. cand., Javastraat 78, 's Gravenhage, 1915.
170 )) » H. C. Siebers, aspirant adjunct-inspecteur der Visscherijen, Pijn-
boomstraat 62, 's Gravenhage^ 1911.
Dr. W. G. V. V. d. Sleen, Stoofsteeg 1, Haarlem, 1915.
D. F. van Slooten, biol. docts., assistent bij de botanie. Donders-
straat b6^i^, Utrecht, 1913.

* » » Dr. C. Ph. Sluiter, hoogleeraar, Nicolaes Maesstraat i'25, Amster-

dam, 1877.
» » M. Spoon, biol. stud., Nieuwenhoorn., Voorna, 1909.
175«]\jevrouw Dr. G. Stiasny-Wijnhoff, Vil Schweighofergasse 8, Weenen, 1906.
De Heer Dr. Th. J. Stomps, buitengewoon hoogleeraar, Weesperzijde 29,
Amsterdam, 1909.
» » Dr. G. J. Stracke, leeraar aan de H. B. School, Ceintuurbaa 249,

Amsterdam, 1900.
» » Dr. A. L. J. Sunier, zoölogisch assistent bij het Departement van

Landbouw, Laan de Rieraer, Batavia., 1907.
» » B. Swart, leeraar aan de H. B. School, Wilhelminasingel 43,
Maastricht, 1905.
180* » » Dr. N. H. Swellengrebel, Binnen-Amstel, Amsterdam, 1906.
Mejuffrouw Dr. E. Tal ma, Nieuwegi-acht 45, Utrecht, 1913.

» Dr. T. Tam mes. Heeresingel 34«, Groningen, 1896.
De Heer Dr. J. J. Tesch, visscherij-consulent, Stadhouderslaan 31, Leiden,
1902.
» » Jac. P. Thijsse, leeraar aan de kweekschool voor onderwijzers te
Amsterdam, Bloemendaal, 1895.
185 » » Dr. K. Tjebbes, Roelofslaan, Huizen (N.H.), 1911.

L. J. Toxopeus, biol. cand., Lomanstraat 68, Amsterdam (vacan-
tieadres: Appingedam), 1919.
Dr. H. van Ti-igt, Witte Singel 96, Leiden, 1910.
W. L. Varossieau Jzn., leeraar aan de kweekschool voor onder-
wijzers, Antonie Duj'ckstraat 58, 's Gravenhage, 1918.
Dr. J. H. Vernhout, Giststraat F 174, Middelburg, 1888.
190 » » Dr. Ed. Verschaifelt, hoogleeraar, Waldeck Pyrmontlaan 4, ^wster-
dam, 1899.

Dr. J. Versluys Jzn., hoogleeraar, Wilhelmstrasse 41, Gtessen, 1895.
D. de Visser Smits, Laan Binon 12, Weltevreden, Java, 1905.

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MejuüVoinv J. M. H. Voigt, biol. oaud., Haagweg 94, LeAden, 1913.
» I. Vooi'molen, Obrechtstraat 552, 's Gravenhage, 191'!.
195 » A. G. Vorstman, biol. carid., Mauritssti-aat 5, Haarlem, 1916.

» A. C. P. de Vos, assistente bij bet Rijksinstituut voor biologisch
Visschei'ijonderzoek, Binnenhaven 86, Helder^ 1917.
De Heer Dr. Ernst de Vries, arts, gesticht Endegeest, üegstgeest^ 1906.
■'■■ » » Dr. Ma.K Weber, buitengewoon hoogleeraar, Eerbeek, 1882.
» V Dr. K. F. Wenkebach, hoogleeraar, Weenen, 1886.
200 De Heer Dr. F. A. F. C. Went, hoogleeraar, Nieuwegracht, Utrecht, 1897.
Mejuffrouw T. van de Werk, biol. stud.. Laan Copes van Cattenburch 92,

's Gravenhage, 1913.
De Heer W. H. de Wette, leeraar aan de Gooische H. B. S., Heerenstraat

15, BussiDH, 1914.
Mejuffrouw A. M. Wibaut, biol. stud., Waldeck Pyrniontlaan 11, Amster-
dam, 1916.
Mevrouw Dr. N. L. Wibaut — Isebree Moens, Linnaeusparkweg 110, Water-
graafsmeer, 1906.
205 Mejuffrouw G. Wilbrink, Cheribon, Java, 1901.

De Heer C. A. van der Willigen, biol. docts.. Parkstraat 49, Utrecht, 19'11.
» » Dr. C. Winkler, hoogleeraar, Utrecht, 1909.
* » » Dr. J. W. van Wijhe, hoogleeraar, Groningen, 1881.

» » S. J. C. V. d. Woude Venema, leeraar R. D. N. S., Appingedam,
1918.

i

T IJ D S C H E I F T

DER

NEDERLASDSCBE

DIERKUNDIGE VEREENIGING

«

ONDER REDACTIE VAN

Prof. C. Ph. sluiter,

als Voorzitter der Vereeniging,

Dr. J. C. C. LOMAN, Prof. J. F. VAN BEMMELEN en

Prof. J. E. W. IHLE.

Sde SEI^IE

IDEEL -X.-^T'XX

BOEKHANDEL EN DRUKKERIJ

TOORUKEIC

E. J. B K I L L

LEIDEN — 1919.

Dj Boekhandel en Drukkerij voorheen E. J. BRILL
te Leiden, heeft uitgegeven :

Tijdschrift der Nederlandsche Dierkundige Vereeni-
ging. Dl. I— VL 2de Serie. DL I— XVII. 8°. 1875—1919.

Supplement de el I. Verslag omtrent onderzoekin-
gen op de oester en de oestercultuur betrekking hebbende f 6. —

Supplementdeel IL Rapport over ankerknil- en

staalboomen-vissclierij - 6. —

Serie 1, Deel I — III. per deel - 4. —

„ 1, „ IV-VI „ - 6.-

„ 2, „ I-XV „ „ - 6.-

„ 2, „ XVI-XVII „ „ - 8.50

Register op het Tijdschrift der Ned. Dierk. Ver-

eeniging, Serie 1, Deel I — ^.YI; Suppl. I en II; Serie 2,

Deel I— X (1875—1908) ,...-. ^' - 1.—

N.B. De Leden der Vereenigiiig wenden zich voor de aanschaffing van het Tijdschiift
tot den Secretaris, Dr. J. E. W. Ihle, te Utrecht.

Ergebnisse, Zoologische, einer Reise in Niederlandisch Ost-
Indien, herausg. von Max Weber. 1890—97. Bnd. I— lY. f 88.—

(Mit 3 col.' Katten, 93 Tafeln u. zahllosen Textfiguren).

Graaf, H. W. de. Sur la construction des organes génitar.x des
phalangiens. ïexte holl.-frangais. Essai couronné de la médai Je d'or
par la Faculté des Sciences de l'Université de Leide. 4"^. / 30. —

Piaget, M. K., Les Pédiculines. Essai monographique. 2 vol. Text,
et planches. gr. 4°. f 60. — . Supplement, gr. 4°. . . . /" 18. —

Snellen, P. C. T., De vlinders van Nederland. Microlepidopterae
systematisch beschreven. 2 dln. gr. 8° ƒ15. —

J3

KOEKDRUKKERIJ VOOrliecn E. J. BRILL. — LEIDEN.

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