Huygens Institute - Royal Netherlands Academy of Arts and Sciences (KNAW)
Citation:
Vosmaer, G.C.J. & Wijsman, H.P., On the Structure of some Sileceous Spicules of Sponges. I. The
styli of Tethya lyncurium, in:
KNAW, Proceedings, 8 I, 1905, Amsterdam, 1905, pp. 15-28
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Zoology. -- "On the Stnlct~t1'e ofsome Siliceous Spicules of Sponges.
I. The styli of Tetltya lyncw'iwn, by Dl'. G. C. J. VOSlIIAEH
and Dl'. H. P. WIJSllfAN, Professors aL the Leiden Univel'siLy.
(Communicated in tbe meeting of April 22, 1905).
Aftel' SCHWEIGGER (:1819) had clemonstrated that the spieules of
sponges in some cases do not consist of calcium earbonate, GRAN'l.'
(1826) fonnd them Lo contain silica, anel BOWERBANK (1841 a) showed
that, in adelition to the siliea some ol'ganie matter is present. He
reaehed this conclusion thl'ough the faet that the spienla when heatecl,
were parti}' earboniseel. KÖLLIKER (1864) remarked that the brown
or black ('olour, pl'oduced by healing, is certainly not only due to
carbonised organic matter; examinecl in rcfleeted light the heated
spicllia appeal' ,vhite, and the dark spots seen in tl'ansmittec! light are,
therefore, partly due 1,0 illclosecl air. THOULET (1884) fOl1l1c! no
ol'ganic matter and concluded: "les spicules sont donc constitués pal'
cle la silice pure", wüich he cOll1pal'es with opal. SOLLAS (18815)
likewise fillc!S that the siliea resembles op al. It is now generally accepted
that the spieules of siliceous sponges consist of some kind of opal;
but that in some way or other, organie matter is also present. So fal'
here is a, general agreement of opinion but the chemical analyses which
have been carried out show considerabie cliffel'ences as to the qnantity
of water, combined with the silica as a gel. The formulae, given
for the composition vary fi'om 2 (Si0 2 ) +H2 0 to 5(Si02)+fI~O,
but must be consiclered as mere failures. F. E. Scr'IULZE (1904) comes
to the result: "dass, entwedel' clie Siphone keinen beslimmten konstanten Wassergehalt haben, oder class die organisthen Zwischenlalllellen . . .. einen je naclt del' vOl'gängigen stärkeren oder gel'ingeren
Austrocknung wechse1nden Gehalt an Wasser haben".
It is certain thai e\'en in the best cases, the qnantity of organic
matter is so little that. it camlot weIl be ascertainec!. lts presence
caB, however, be proved by trenting the spicules with hydrofluoric
acid. But t11ere is a180 some clisagreement as to the nature of this
matter anel the exact jJlnce in thc spicules where jt is met with.
We shall see that different kinds of spictlles vary in this point.
In adclition 1,0 the silica, whieh Lehaves like some kind of opal,
and which we propose to call spicopal, anel the organic matter which
F. E. SCHULZE calleel spiculine, - modifying the origiJlal term uscd
by HAECK]t]L - in some spicules thel'e have been fonDd traces of
Na, K, Cl, Fe, Mp; n.nd Oa, but in sllch slight qnantities that they
can be left out of cOl1sideration 1'01' the moment.
,....
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As to the structnre of the spicnles, GRAY (1835) had found them
Ül Hyalonema. to eonsist of, layers, which became conspieuous by
heating. These layel's concentl'ically sUl'round a."central canal", which
is filled out, as KÖLLIKl!lR (1864) has sho,vn, by an organic mass,
the axial rod. CLAUS (1868) fonnd that the silica which directly
sUl'l'oundl::i this centrall'oc1, is homogeneous j he callec1 this homogeneons
cy linder t11e axial cylinder. According to lVIAx SCliUL'l'ZE (1860) the
10ngiiuc1inal striae, which become ronspicuous especially aftel' heating,
are due to the fact th,at layel's of silica altel'nate with very thin
hyers of organic matter j the first are, aftel' SUI-IUL'l'ZE, isotropic,
the secOlld anisotl'opic. The outer layer is generally found to be of
ol'ga,nie nature.
In all these eases, the investigators described some special kind
of spiClüe; naturally they have chosen very larg'e spicl1les. GHAY,
CLAUS and MAX SCHUL'rZE studiecl the large rods of Hexactinellida,
sueb as Jlyalonem,a and Euplectella. It may be asked; how far
their reslllts hold good for spicules of other sponges.
KÖLLIKl!lR had already found that not in every case tile axial
threacl is conspieuous. Also it has not been possible to c1emonslraie
in every case alternating hyers of spicopal aud of organir. matter,
not even whel'e longitndinal lines are evident. There is a greai
confusion with regard to the presence of a so-callecl spicular sheath.
An)' accurate determination of the 'refi'active power of different
spicules is likewise wanting.
It seems, therefore, clesirable to get some more information ab out
these subjects. Since F. E. SCJIULZJ~ (1904) stuc1ied the enormons
spicnla of jllonod~aphis, it appears usefuI to investigate, whether
spicules fl'om other grollps agree with them as to their structure,
and thei1' che~nical and physical properties.
..
We began our examinatioll by the large styli of Tethya Zynczt1'inm. Aftel' bringing this point to some certainty, we have compared the resltlts with those obtained from other species.
In the first place we tl'iecl to answer the question: Do the styli
.of Tethya contain othe1' organic elements than the central rod, èither
as a sheath, Ol' as layers between the spicopal, or as both of them.
Of COUl'se, the method w hich at first presents itself for the detec'tion of orga,nic matter, is the dissoilltion of the silica/by m~ans of hydrofluoric acid. Former investigators who appliec1 this reagent, have
omitted to give an accurate deRcription of thei1' experiments. SOLLAS
(1888 p. XLIX) put the isolated spicules into a drop of water aud
added a drop of hydroflno1'ie acid. On doing this, one generally
sees that the silicu is dissolved and that thc central rod remains.
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Adding 1ess hydl'ofIuol'ic acid, the pl'ocess does not go to the end. As
it is necessal'y to cover the sIide by means of Oanada ba15am (SOLLAS)
in order (0 pl'eSGl've tIle object glass fl'om the c1isastrous influence
of the vapoul's of hydl'oflnOl'ic acid, it is difficnlt to val'y the acidity
of the fluid, in which the spicl1les are monnted. Also H is impossible
in tbis way, to exclucle the in.fluence of the glass. We had therefore,
to COJlstruct all appal'atus allowing the concentration ofthe hydl'ofluoric
acid to be val'ied withont danger 10 the lenses of the microscope.
At first we tried ebonite, in combination with glass, covered by a
layer of celluloid, which is sold in solution nnder the name of zapon.
But as th is method clid not satisfy our pUl'poses, we tl'ied anothel'
and wc tlünk thnt we lmve fOl111d a good and rather simple device.
The adjoined fIgul'è needs little explanaiion. Out of a sheet of trans-
~~
"
{",;""/",,,;;I;d
cf.'
pal'ent celluloid, 1 mmo thick, is constl'ucted a case, abeel 1); the
bottom measmes 6 X 10 cm., the height is 1.5 cm. In the midst
of the case a cil'cnlar l'im of celluloid, high 5 mm., is joined to
the bott01l1. Anothel' case of celluloid a'b'c'd' measures 4.5 X 6 cm.
bottom anel 8 mmo height. In th0 midelle of the bottom a square of
2 X 2.5 cm. is cut out, This opening is covereel by a sheet of thin celluloid, no more ihan 0.5 mmo thick, mel1suring 2.5 X 3.5 cm. This
thin sheet A is joined with b'c' air- anel watertigllt by means of soft
paraffin. 'fhe spjcules nncler examinatioll are placed on the bottom
of the Cl1se a'blc' dl, e. g. in a drop of water. Ta fll1tten this drop
it is coverecl by a very thin film of celluloid. In the exterior part
of the case abeel is pOl1l'ed out some liq uiel pamffin IJ, iu the interior
commercial hyc1l'ofluol'Îc acid (jl), diluted with 3 Ol' 4 parts of water.
Now the case a'b'dd' is reversed anel put into rtbcd, As we have
fonnd that hydl'ofluoric acid in the g-aseous state aftel' some time
1) The carefully cut and clealled sheets of celluloid are easily united by means
of acetone. Tbc pm'ts that should be united are pl'essed together, and by means
of a small hrush a little drop of acetOlle is applied. The celluloid immediately
sticks togeUler. The corners are afterwal'ds, to diminish the chance of Ieakage,
cemented anolhel' tim~ with zapon. Celluloid is got at the D. Celluloid Fabrik
Leipzig. .
I) Vel'y LllÎn films of celluloid arc got by pOUl'illg out zapoll on a glassplate,
in the way thaL collodion pJalcs al'C madc, aml Leal'ing iL 011' the glass aftel' cll'yillg.
2
Proceedings H.oyal Acad. AmsLerdam. Vol. VIlI.
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passes thl'ongh thin strata of celluloid, it lliight be expected that
the very thin !ayel' of celluloid used in the above manner woulc1
be 110 obstacle for the acid to attain the spisules. Even the retaining
of the reaction in this way is an advantage, as it may now be
observed without the use of very dilute solutions.
In this way we have constrllcted a liWe appal'atns whielt has
answered to OUl' pmposes in several rei:ipects, viz: absence of glass,
slow reaction, rather gl'eat security for the lenses of the microseope,
and the possibility of interrupting the reaclion at any moment .
. As we found it unmatel'ial whether the spicules (obtained ti'om
sponges pl'eserved in alcohol) were isolated by met'LUS of artificial
gastric juice (aftel' some -dnys t'Lt 35° 0) Ol' by boiling wiLh hydroehloric acid, we prefel'l'ed the latter method. Snch spicnles, having
been boiled with hydl'ochlol'ic acid fol' SOllie minutes, washec1 out
repeatedly with water, either with the aid of a centrifuge Ol' not,
and dried afterwards at the orclinal'Y tempel'atllre, are the objects
investigatecl by us, if another tl'eatment is not expres5ly mentioned.
Hy placing SOllie spicules in a drop of water, and covering them
with the thin film of celluloid, one ean first stud)' lUl del' the
micl'oscope whether they are nOl'mal in their aspect, uninjl1l'ed elc.
Also, and Tethya is a proper ob.ject for this, which spicules are open,
which closed. Then we expose the preparation to the vapoms of the
hydrofluol'ic acid. The commencement of the reaction i::; more or less
retardecl, depending upon the concentl'ation of the acid, the quantity
of water'anel the thickness of the film of celluloid; buL at any mte
the spicnies begin to be dissolved aftel' some 30 Ol' 50 minutes.
It Üi best /0 give attention to the fractmes, as the l'eaction i~ here
to be aeen at th·st.
BÜ'J.'SCIITJI (1901) all'eady remal'kecl that tlle clissolntion of the silica
may oceur in different ways. We can confirm th is obsel'\'ation for
the styli of 'Tetl"ylt. ObSel'Ying what happens at the broken end of
a spiclllnm, the opal Slll'l'OUlldillg the axial thread is seen to be,
_hoUowed out in the stw,pe of a cone. The top of the cone is very
shal'p, and becOlnes still shal'per if the reaction proceeds. BÜTSCHU
says (1. c. 258-259): "Man könnte wegen diesel' so hänfigen
Hildung einer tl'ichterföl'll1igen Auflösungshöhle an den Enden auf
die Vel'muUll1ng kommell, class die Allgl'eifbal'keit und Löslichkeit
del' Schichten von aLlsscn nach innen, gegen den Achsenfaclen successive zunehme. Eine solclw Anuahme scheint jecloch znr Erkläl'ung
-del' El'scheinung nicht llöthig, vielmehl' -dü.l'fte sie sich schon c1araus
hil1l'eichend erläntel'l1, dass die l!'lusssäme almähIich in den geöfi'neten Achsenkalln.I einclringt uud gleichzeitig auch ill dem l\1asse
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stäl'kel' wh-kt, als der Aëhsenkanal dnrch AnfIösnng erweitert wird,
indem Chl.ll11 eine grössel'e Menge der Säure znl' Vel'fügung steht.'~
We believe, on tbc contra!")', thai it really follows from the observatioll that tbe jn'ner parts of the spicopal are more easily dissolved
than tüe outer Ol1es, For we see the sharp conical funnel long
befol'e auy tl'ace of reaction is to be seen on the rest of the fraeture.
Tbe borders l'emain intact for a considerabie time. And we get the
same view by boiling in a solution of eanstic potash. OnIy when
the conical hole has attained a certain depth, the dissolution of the
spicuillm from the e:x.terior commenees. Finally there l'emains a
kind of tube, formeel of silica in which the axial thread is laying
isolated, lU1til all the spicopal has eIltirely passed into dissolution.
If we study the way in which the hydrofluoric acid acts on completely intact spicules, S0111e difference may he seen, according as we
ha ve to do wi th sharply poin ted l1eedles Ol' with those of w hieh the
apex is ronndeel olf. Blunt styli, i. e. transitions to strongyli, resist
the acid for some time; but once the dissolution has beglU1 from
the exteriol', the pl'ocess pl'oceeds regularly, the Spiclllum become8
thinner and thinner,
It seems that in pointed styli, the apices are first attacked; in
sllch cases we Ree the axial thl'ead gl'adually comil1g fl'ee by extel'nal
dissolutioll of the spicopal. Sometimes it may be observed that, in
addition to the dissolving nl'ocess as described above, a hollowing
out along the axial thl'ead takes place. In other cases, however,
this is not seen, and we get half dissolved spicules in which the
axial thread is partIy freed, partIy enclosed in a coat of spicopal,
thus stl'ongly l'esembling whjps; the more so as the !11l'ead is generally flexible, whel'eas the l'est is still straight and rigid.
BÜTSCllLI has already l'emarked that the1'e are sometimes seen "durch
lokale stärkere Auflösung del' Kieselsubstanz zellenartige Vel'liefUllgen
del' Nac1elobel'fläche". "1nc1e111 diese Vel'tiefungen sel11iesslieh zn Löchern
werden, die bis zurn Achsenkanal l'eichen, wird diesel' del' Flusssäure
zugänglich und nun beginnt von diesen Löchem cles KaJJals aus . . . .
die innel'c Auflösung del' Kieselsubstanz l1l1ter Entwicklung zweier
tl'iehtcl'fOl'migel' Höhlen .... " This obsel'vation we eau confirm j we
consider it anot11e1' proof that the spicopal in the neighbourhood of
the central tlu'ead is more easily dissol ved than the pel'ipheric mass i
the obsel'vation can hardly be explained in another way.
Spiculcs, dissolveel in the describecJ way, show, thai there remained
not only aftel' the c1issolntion of the spicopal an ol'ganic central thread,
but also a vcry thin coat, which covel'ed the exterior layer of the
spicoptû. This coat, which l'epl'esents the true spicule sheath, is
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extraordinarily delicate; consequently it is easily torn Ol' shrunk.
Still, we are convinceel th at it exists, bnt the examination mnst be
carriecl out with the u1most care. In some pl'eparaLiolls we fOlllld it
in the greater part of the objeets. That it is not always obsel'veel
may pal'tly be due to tho tl'eatmeni of the spicules with hyelrochlol'icaeicl, partIy by iis being c1estroyed alreacly cl uring the lif'c of 1he
sponge. The axial threael i::. likewise not always visi\:lle, Ol' at least
not over the w hole lengtll of the spiculum. On carefully dissol ving the
spiculllm iL may be observecl that, while tho cylinder of siliea gl'adually diminishes its diametel', a VOI'y thin line shows tho ditnensions
it originally possessed.
'Yhen the spicules are observed in water, the limits show themselves as mther broael blad: bands, as tbc refractive iliclex of the
spicopal is cOl1siderably higher than that of water. 'Yben the dissolving process goes on, the black banels gl'aelually approach each other,
anel the thin line, the optical section of the spicule sheath, becomes
conspicuous. Whell the object is now studiecl in aciel fuchsine, tho
central thl'ead stains intensely red as it is set fl'ee, anel the shoath
becomes faintly reddish in the mean time. Ol'ganic layers, so callecl
layers of spiculine, sueh as can ea::.ily be demonstrated in the large
needies of Hexaetinellida, are nmvhere met with in Tet/Lya. In some
cases we saw something whieh resemblecl them, but in overy ease
we eoulcl explain tho phenomenon by a .rolding of tlle sheath. Oonsequently we conell1cle that layers of ::.pienlille al'e absent in Tethya.
Anc1 we eal1llOt agreo with MrNcIlIK (..:.900), who says about spienla
in genOl'al" (1. e. p. 40): "the minel'al maiter is cleposited l'ol1nd it
(viz, the axial thl'eael) in concentrie lamellae of colloid silica, alternating with lamellae of ol'ganie nature".
As to tbe spieule sheath, wl'Ïters do not agl'eo. What F. E. SCHUL7,l~
caUs "Spiculaseheide" in bis last pnblication ('1904) is not homologous
with what we indicate with the name or sheatll. That we notwithstanding use this term has historical reasons, as it seems to us that
the word is ol'igillally llsecl fol' forl11ations belonging to the spieule
itself, homologous io iho pl'odnct whieh i::. found in caleal'eous spicules,
whel'e its existence had been first demonstrateel. In this sense
MINCJIlN applied t11e term, anel he is the author of the llewest anel
best general tl'eatise on POl'ifel'a.
KÖLJ,TK1~R (186-:1:) may be l'egal'deü ns the diseovel'el' of tbe spicule
sheatlf . Tt seems to us beyond doubt what KöLUKmt meaut by it,
although we acknowletlgo that his opinion is not alwa.ys oxpl'essod
with ihe utlllosL cleal'lless, and that .from 1he beginning there had
existed ::.ome confusion of ic1etl,s about this ol'gan.
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says (1. c. p. 64-65), spcaking about "Na1'doa spongiosa":
"Ausserdem finclen sich clnnll noch nach del' Auflösung der Spicula
dm'ch Essigsänre, zahll'eiche Lücken, welche diese Bildungen enthalten,
die allen von einel' scharfen Linie begrenst sind, wie bei Dunstm'Vilia.
Bei lVa1'CloCl g']aube ich ll1ich davon überzengt zu haben, dass diese
schade Linie der opti5che AnsdL'Uck einer selbstandigen Scheide del'
Spicnlo. ist . . ." Wrüat KÖJjw,:Jm means by the word "selbständig"
bE'comes elear when we read that in eveL'y canal spicules project,
in wbich, aJter tl'eatment with acetic acid, ('an der Stelle des in die
Flimmercanäle hineinragenden Stmh1es der genannten Spicu1a zarte
Scheiden leer zurück (bleiben)" . These sheaths are, according to
KÖJjLIKER, perhaps a "Rest von Bilclungzellen." However, he adds:
"freie SpiClllo. zei gen , del' Eimvil'king der Essigsäme ausg'esetzt,
keine solcbe Scheide .... " "W"hat is meant here with "freie" spiculo. is
not eyiclent. It ca,n hardly mean anything else than isolated spicu1es.
If they be isolo.ted mechanically, the sheath is as obyious as in
spicnles in sitn; if they be isolo.tec1 chemically, then of course the
absence of a sheath is no proof at all.
It is easy enough to repeat KÖLJ.lKF.RS experimenls, especially in
using specimens with thin walls, as e.g. Leucosolenia. If a fragment
of a wide tube of L. t'1t7'i(tbilis which bas been cut open, is spread
out in water nndC'r the microscope, and carefnlly treated with acetic
acid, the cal'bonate of lime is seen to be gradually dissolved, and
soon tho shcüths, with sbnl'ply defined outIines, exact1y as descl'ibed
by KÜIjT,JKl<}R, are visible. The sharp outlincs are especially clear
on spols where the spicnles are "wholly eJlclosed by parenchyma; in
projecling spicules the conical shoalh of spicllline is seen to remain
as a homogencous, extremely thin film; still more stl'iking, perhaps,
is the phenomenoll if the spon ge is stainod on the object glass, e. g.
with cal'ma1uml1 (GRÜTlLm~). 'rhe cal'malnmn, whieb is genemlly somewhat acid, causes the rülcite lo dissolve, tl,nel stains the sheath p111'p1e;
the slml'ply clefined outlines (optica1 sections) appeal' dal'k-purp1e,
while the projecting spicu1es are fainLly pmplish. If sucl! pl'epamHons are examined in glycerine Ol' in Canada balsam, the spots
w here the carbonate of lirne lms been dissol ved, Ol' "\vhere it is still
present, are hal'dly to be discerned. 'Vhen we use the polal'ising miC'l'oscope, howeve1', the presence of calcite becomes immediately visible.
Consequently, there l'eally exists a special layer of ol'ganic subslance
which tightly covers the spicul$3, "\vhich can be isolated with tbe spirulum,
but which cannot be sepamted feom i.t othel'wise than by dissolving
the carbonale of lime. Doubtless it is this organic layer which
KÖLLIKER called "Seheide" . In this sen se also MINCHlN uses tbe word.
KÖr,IjIKER
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The question now al'ises how 1[\,1' siliceous_ spicules are likewise
enclosed br sllch organic coats, homo10gous to the sheaths of the
calcal'eous spicules. W'e are of opinion that Jhis is aciually the ct1se;
the delicate organic film whirh we found rovering the spicules of
Tethya we con si del' as the homologon of the spicule sheath of
('alcareous spicules. Such products have been aireacly observed. Nou
(1888 p. 16-17) says: "Noch ist für clie Spicula von Desmacidon
Bosei eines Ueberzngs von organischer Substanz Envähnung zn thun,
. . . . . Hauptsächlich nach Behandlung' del' Präparate 'mit eÎl~er
Höllensteinlösung . . . . weniger deutlich mit Acidum pyrophosph oricum , manchmal auch mit Pirrocarmin wurde derselbe sichtbar.
Stifte, die isoliert, o1111e Ueberzug von vel'kittenclem Spongin, über
die Hälfte fi'ei aus dem Schwammgewebe hel:vorstanden oder anch
solche, die ganz' ti'ei lagen, waren besonclers nach del' Silberfàrbnng
gleichmässig mit einem lichtbrannen Uebm'zuge verRehen, del' trotz
seiner geringen Dicke doppelte Kontlll'en erkennen liess und die
Stifte gleichmässig übereleckte . . . . Die Spi('nla von Desmacidon
Bosei besitzen a1so einen homogenen hautal'tigen Ueberzl1g VOn
organischer Substanz, der verschieelene Farbstoffe aufnimmt. Wil'
wollen ilm als Spicula-Obel'haut bezeichnen . . . . " Although NOI,L
sees in this coat something else than what KÖLUKER found in calcnreous spicnles, we suppose them to be equivalent. Just as KÖLLIKER
indica.les that his "Sclteido", is perhaps a "ResL von Bildnngszellen",
sa Nou, writcs that his "Oberhant" may be "der Rest der die
Nacleln bildenelen Ze]] en" .
SOLJ,AS desrribed in the same year (1888) snch a 8hoath, which
became perceptible aftel' tl'eatmeni wHh hyelrofll1ol'ic acid. Descl'iption
anel drawing (I. c. p. XLIX, PI. XLIII, fig. 18), regarding the
spicule of "Doryplel'es Denclyi", leave nOihing to be desÏl'ed as to
clearness" "AJthough at first sight the acid appeal's to l'emove all
the substance of the spicule except the axial rod, cal'efnlobservation
will show that ihis is not the case, fol' a delicate film of ol'ganic
matter also remains behincl; it has the form of a hollow sh~ath,
cOlTesponding in form anel posit,ion with thc ontermost bonncJal'Y of
the original spicnle; betwccn it anel 010 axial rod Lhc wholc of the
spicnle is completeI)' r01110Ve(]. The spicnIe thus consisLs of a ccntmI
organic axis, surl'olluded by coneentl'ic hyel"S of opaI, t he ontCl'\lIost
of whiel! is Îlwcsteel in a spicnIo sheath of Ol'ganic maller Ol' rather
of Ol'ganic matter in intimato associatjoll (chemical llnion?) \VUh
silica". Om resnHs regarding tbe pl'esence 01' sneh a sheath in
spicnles of other species "'1'0 hope to give in n next pllblication ; for
tbo pl'e&eut we deal on[.)' with the spicu1es of l'etlt!Ja.
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It IS eviclelif, that if we are rig-ht in OUl' conception of the spicnle
sheatl1, othee coats which sometimes are fonnd SIllTolU1ding spicules,
. may not be callecl sheaths.
F. E. SCHUJ,Z]~ descl'ibes in his last paper with his weU lmown
accuracy such snrl'onnclings feom the enOl'lllonS needIes of ~Mono1'1lap7tis. We l'egret not to agl'ee vdth him in caIling this formation
"Scheicle". As SCIIUI,ZE demonstrated it to be not only an investment
of each spiculml1 for itself, but also a means of joining different
spicllles togethel', anel as this is trne for otber spicnIes also, we propose
to ca,][ it lJel'irtpt 1). SOUAS (1880 p. 401 2) described a similar coàt
surrounding spicnIes ~from hops phle/}raei. BÜ'l'SCHU found it in
Tethya lync~l?'iwn, tt fact which we can' confil'm. The periapt is
composeel of conllective tissue with cOllspicuous fibrils and cells;
it has Lhel'efol'e, llothing 10 do with the spiclIles as sncl! and may
be 1eft out of consic1eration here. Mutatis mutandis, the periapt
behaves to the SpiCtlle sheath as a perimysium to the sarcolemma.
We have seen alreaely that when the spicopal is c1issolveel first of all
the axial rod appeal's. The pl'esence of such all organic thl'ead in
macroscleres is 110 more doubted. AIthongh we have no mo1'C
doubt that the axial thread is normally present, it cmmot be c1enied
tho,t in some cases it is wholly or partIy absent. We cOllsidel'
snch cases, howevel', to be ptLthologictLl.
Wïth regard to the shape of the roei BÜTSCHU (1901 p. 253)
Wl'Ïtes: "cigcnthümlich Ü::it dtLS Qnel'schniUsbild eles Fadens, das •...
stets dcutlich c1reieck.ig el'schcint, gleichgültig ob der änssel'e Umriss
des NtLclclqnerschnitts sclbst CLWtLS dl'eiseiLig ocler ganz kreisrund ist.
Viclfach ist jecJoeh auf den Nnc1elquersehnitton zu crkcnnen, class
der Qnel'sehnitt des Ael1senfnc1ens scchseckig erscheint, indem die
Ecken dcs cll'eiscitigcn U llll'isscs l'egelmüssig abgestumpft siml".
Conseqnently, the centml thl'etLd in such cases, e. g. in Tethya,
would be a triaJlg11lm' rod and not a CJ' lindel'. Wlwreas all'eaely
BO"·BRBANK (1864) appm'ently htLel seen somcthing like this in Gemlia,
F. E. SCnUJ,ZE (1904) m'l"ived at the concIl1sion tlmt the axial threads
in HexactinellidtL are c:rlindric. In view of this contradiction \ve
thought it 11eCeSSal'y to submit the axial tlu'ead of Tetltya to a
cal'eful invcstigation. In order to juc1gc about the shape of a thread
in transverse section, we followed tho method of BÜ'l'SCHU by grincling
spicules in tLn agate mortel'. In the powder, pl'ocured in this way,
th ere is foullCl alwa.rs a snfficiellt qnantil.y of particles of approximately
I
1) ;r,
pi X 7rT"1JJ I bind together.
Not 1890; - uppul'euLly this is u mispl'Ïnt in
not p. 410-4.41 but 400--401.
2)
- 10 -
SCliULZE
(1004 p. ~04), -
also
( 24 )'
eylindrical shape, alt.hough 1.h:1t thc fmcinre is irregulal'. If thesè
pieces al'C mounted in glycerine,l) it is possib1e, as the spicopal almost
entirely di&appeal's froll1 the eye, to jndge with cel'tainty in which
POSitiOll the thrcad is seen, "vhethel' obliqne Ol' not. Paying tlJttention
only to those whiel! are nndoubtedly seen in transverse optical section,
we found by careful focussing that iItey were really tl'iangnlal' with
the angles ent off. In the second pl:we we stl1died isolnted axia.l
thl'eads. By moving 80mewhat the coverglass, a quantity of little
pi~ces break oif, genel'ally a1m08t transversely. At the sawe time
it can be observed th at the little fragments turn over, owing to the
movement of the fluid. In this way we saw plenty of them from
all sides. With high power (Zeiss, homog. imm.) wc found that in
this case also tbe transverse section is t1'Îallgular. In spite of OUl'
astonishment that the axial rod in Tethya is tl'iangnlar we cannot
but agree witb BÜTSOIILI'S observations. We did not see varÎCosities
nol' shal'p restrictions; normally the isolatecll'ods are perfectly smooth.
The diameter remftins the same, with exreption of tJle extl'emities;
these are, in uninjul'ed threads, either sharply pointed Ol' rounded
oif, according to tIle weIl 1010wn sllape of the styli themselves.
Deviations of this l'ule seem to ns to be pathological.
Not less strange than the Rhape appeal's 10 be, is the C'onsistency.
This may be the reason that pl'evious authol's so liWe agl'ec. 'iVheren.s
wc fincl, aftel' tl'eatl1lent wiLh hydl'ofluol'ic acid, that tlle fl'ce axial
threads on one hand are vcr,}' flexible, so that thoy cnn form clews,
we flee on the olhel' hand that ill many cases they break off at Ollce
if touched with a needIe. 'iV e remarked aJl'ead.r that they gcnert"tlly
break at right anglcs to lho axis. In a cortain sen se BÜ'l'SCIIT.I is
right, thel'efol'e, if he caIls th cm "sprocle", but it is by no means tho
sort of bl'ittleness of 1'01' example a tbl'eac1 of glass. The consistel1cy of
the axial thl'ead can be best comparecl witl! ag:1l'-agal'. Here a certain
tlexlbility is likew1se combined with lhe pl'opel'iy of suddenl.)' breaking. Sil1111a1' phenomena are known of gels at a cel'tain point of
dehydl'ation.
The axial rod in Tethyrt is, taken as a whoie, not homogel1eous.
Fi1'st of all we obsel've, especially in thl'cads siained with iocline, a
double contour. 'l'his is easily clemonstrated on llninjnrod, i80latecl
thl'eads as weU as in transversc sectiol1s; in (he (l'ianglllal' figUl'e,
nTelltioned above, the wall is both inside and ouiside tl'jangnJal'. This
wall is compal'atively thick - about 1/4 Ol' 1/6 of tbe tot:1! diameter.
We may considcl' t11e nxial thl'ead as n tube, fillcc1 wiih something;
I
J.) Reft'active index
11
= 1.4508. Cf. infm.
- 11 -
(' 25 )
wheeeas the ",yall seems fo be homogeneons, the contents are h01110geneous or rather gl'anulal', apparently of a softer consistency than
the ll10l'e rjgill wall. This we conclnele ft'om the fact thai cUl'vec1
Ol' bent axial ihl'eadR unc1er tbe microscope l'esemble cUl'veel or
bent indim'ubbel' tubes, fillerl with a flnid or semi-fluiel snbsiance.
Soliel, flexible cy linc1ers never show such abruptly bent fignres,
A remal'kable phenomenon is 10 be seen in broken spicules under
the influence of hydroflnoric acid. As siated above, the spicopal is
dissolved in a peculial' way, the central canal being hollowed out
in the shape of a fnnnel.' If we now only take inl0 consideration
the cases where the thread is broken at 1.he same place as (he
spicopal, we see the thread gradually shl'inking somewhat undel' the
inflnence of the hyelrofluoric acid. However, the wall anel its contents
do not shrink equally. The resnlt iR that the contents somew11at
pour out beyond the wal1. It is not improbable that BllTSCTILI JU1,S
seen tbis; at least his illustraiion (fig. 24 on pI. XXI) strongly
l'esembles what we nbsel'veel. But BÜTSCITU expJains it in anotbel'
way; he believes the ihreac1 to be l'estricted "manscheltenfórll1ig".
According 10 BÜTSCHU the axial thread consists of a proteid
substance. 'Vith F, E. ScnmzE we can confirm this in the main
points, Boiled in Mn,LON's flnid the thl'eads in grolmd spicules turn
yellow. This staining is especia11y c1istinct in pieces where a part of
ihe threacl itl lost, allel where, cOl1sequenlly, the axis of thc spicnlc
is partly llnco10urecl, pal'tly filled with a yellowish thl'eacl. Isolatcd
axial thrcads or thl'eae!s partIy freed by soln1.ioll of tlle spicopal m'e
casil)' siaülecl with ioe!ine. Trea(ed with nitrÎC acid (25 0/0) they
swell somewhai nnc1 acqnil'c a fi:tinL yellow colou]', which becomes
elarkel' by snbseqnent aclclition of ammonit1,. Hcated with llitl'ic acid
thc thl'cacls clissolve; 1ikewise Ül canstic potnsh. vVc may ('OJwlnc1c,
therefore, thai ihe central rod if not wholly, at least. pal'll.r ('onsisls
of some ]1roteiel. Obscl'vcd nndel' the polal'isatioll micl'oscopC no
trace of anisotropy eould bc seen.
Wïth l'cgal'd to the slJles of Tet7tYrl (lj77CZl1'ill7n we tlms arI'Ïvec1
at ihe çonc1usion, that they are composee! of au organic axial !lu'ead
anel an Ol'ganic spicule-sheaih, bet\veen which eJcments ihe spicopal
is cl eposiieel. \TV c fi:tilee! in demonstrating allJ tmce of ol'ganic (spicnlille)
1ame11ae. But still we founcl, {hat llndcl' specÏ<ü cil'cml1stanecs
longiine!inal, resp. concenhic siriae wore disiincily seon. 'V0 have
10 look for all cxplanation of thi8 fad.
In order 10 avoid a possible misllllclerstanding or confusion we
wish at once io draw atlention to the fact., hithel'io mihet' neglccted,
thai 011_0 has to distinguish the various layel's of spicopal from their
- 12 -
( 26 )
limiting plaim. We hope to show that Lhc well-l{llown stl'ipes Me
nOLhing but the optie sections of snch limiting p1ains, alld that they
are independent of eventual diffel'ences of the layers. It is easy
enollgh to microscopical1y dCl110nstrate such lil11i1.ing plains in layers
in al'tificial siliceous gels. If a coat of not yet coagulated siliceous
gel is poured out over another one freshly coagulated, and if this
is repeated, it becomes evident that the consecutive layers of ge] in
the begilming do not uni te. Only in drying the 1ayers become one
mass; still, in seetion the limiting plains are very conspieuous. This
experiment teaches us that in a siliceous gel a lamellar structure
can appear, wherein the conseeutive layers are separated by visible
limits, without interference of another substance e. g. of an ol'ganic
lamella. We will come back to this faet later.
Several ways are open to us for the study of the spicular stl'ucture,
but they are not easy. Besides dissol ving the spicopal by l11eans of
hydrofluorie acid and carefully watching the proeess, the method of
beating has been applied since GRAY (1835) showed that this brings
out more distiuctly the lamellal' structure. Im'IA (1901) was the first
to point out the effect of different media. We shall see, that some
spie nIes mounted either in Oanada balsam or in glycerine, so widely
diffel' in aspect that on first sight one believes that Ol1e has to deal with
enii1'e1y different SOl·ts of spicules. 'V- e thought it necessa!'y, therefore,
to begin by determining the refraetive index of spicopal of val'ious
spicnles somewhat more accurately than hitherio done. As far as
we know of there exists no other infol'mation than given by SOLLAS
(1885), who stat es in general tlw,t "the l'efractive index, of spongesilica is . . . . that of opalor colloidal silica, and noL of quariz",
and that the spieules come neal'est to invisibility when "mounted
in chlo'roform, whieh possesses a refmcti\'e index of 1.449".
In determining the l'efractive index of the spieules we used the
method, since SOUAS generally I1sed also in mineralogy, viz. to find
in what Duid the spicule can no longer be seen. Perhap" there is a
still beitel' cl'iierion to make ont how ml1('11 a spicnle cliffel's fl'om
Hs medium anel in ",hich direcUon, viz. the appeal'ance of eoloUl'ed
borders. -- In order to avoid the effect of fluids wich llIight influen ce the amoullt of water eontainecl- in thc spieopal, but, on the
oiher hand to demonstrate jUSL this influence, wc usecl fluids whieh do
not mix with wnter as weIl as such which were dilnted witIt water.
The refl'acLive l1lclices were determined by the refractometer of ABBE,
which has "'the great advantage of enabling us to work with ol'dinal'y
daylight and to determine any nu 111 bel' ofinclices, botween the microscopical work. In spiLe of the apparatus of PUL1!'RlCH being more
- 13 -
( 27 )
n(,cUl'ate we tlsed, thel'efol'e, au Amw, the more so as it tnrncd out
to be sufficielltly accurate for OUl' purposes.
Among the fluids, not mixable with water, we took aclvantage of
the series liql1id pal'affin (n
1.4759), petl'oleuii1 ('12
1.4568),
benzin (n
1.3994) and petrolenm-ether (n
1.3780).
We succeecled by .llsing mixtmes of petroleum and benzin in fixing
thc refractive index of the spicnies at 1.4508--1.4510. In order to
give an ielea. of the degl'ee of nccuracy that. can be aUainecl in this
way, we may state tbat undollbteclly a elJfference is to be seen bet\yeen
spicules, mountecl in a mixture of 20 cc. of petroleum with 3 cc.
of benzin (n = 1.4500) anel mOlmted in a mixture of 20 cc. of petroleum with 2.5 cc. of benzin (12 = 1.4510) . .13'01' a aqueons watery sointion
we used dilute glycerine, anel iound with this medium also a complete disappeal'ance at n = 1.4508. In acldition to these media we
stndied the infl.uence of air, methylic alcohol, water, potassiu1l1 acetate,
(,l'eosote, oil of bergamot, vcnetian turpcntine, oiJ of reel ceel al' wood,
oi1 of lemon, oil of thyme, firoil, oil of pepperminI, oil of cloves
(pl1l'e or mixeel with nlcohol), Oanada, balsam aI).cJ monobromnaphtaline. Practirally however, we uscd more especial1y the LWO
fluids mentioned above.
In glycerine with It = 1.4508 incleecl the spicopal of some spicnIes
disappeal's completely, n.nel only tbe axial rod remains visibic as a
light blnish thread. In all styli, the central thl'ead has a higher
l'efi'acti\Te incJex than the spicopal. By cal'eful examination (Zei ss
Apochr. 8.0c. 4) in most spicules a light, shal'p line may he seen
as border, anel a system of longiiudinal slI'Îae bet ween the axialrocl
anel ihe bordel'. 'Vith Iow power the lamelJal' stl'uctnee does noL
become conspicuous, tllongh the bOl'derlinc is sll11 vit,ible. Mos/,
probably IIlis thin 1ine, which exhibits dOllble contoul'S with high
po wel', l'epresel1is the organic spicnIe Rheath.
By these experiments i1. beCOll1eS at the same time yery evident,
that ihe axial ihl'ead cau be partly absent; on these spots tbe
light bluish band (the central rod) abruptly ceased. If the glycerine
has entered int.o the central ('anal, only an indica(ion of the spicopal
is visible; if air has entered, of comse this is directly visible
by the lo~vel' l'efl'action. 'fhe aspect of styli isolatecl by means of
boiling with hyell'ochloric acid, eithel' witii aclclition of poiassiull1
chlorate Ol' without, Ol' by digestion by means of artificial gastl'ic
jnice, Ol' by hea1.ing wiLh sulplllU'ic acid aud potassium-bichl'Oll.ate,
fundn,mentally agl'ee.
Quite anothel' aspect is sllOwn by spicules which have been dricd
fol' sQll1e clays in Uw pl'esence of anhydl'ous phosphol'ic acid. 'Ve have
=
=
- 14 -
=
=
( 2$ )
studied spicules which llltcl been clried in t]lis way fol' sorne dayfl
at an ordinal'y temperall11'e, and a1so in VWTOR 1Vl:Imm's to1uo1 bath
at 104°. The heatil1g, howe"e1', had no inflnence on the aspect.
Thc determination of the refractive index is a UWe less accurate than
with ol'c1inary spicules, becanse on dl'yÎ11g the lamellar i)tl'ucture had
become somewhat more conspieuons, anel thel'cfore t.he disappearal1ce
in glycerine is a little less perfect. Still we could determine in
petroleum-benzine the l'efl'active index n = 1.4052-1.4055; with
dilutecl glycerine the same resu1ts were obtained.
. Tf the dJ'ied spicnles, ll10unted in glycerine with n 1.4055, anel
with the border of the covel'ghtss weli simt by means of vaseline,
are left to ihemselves, gradually ft'om t.he outside the refraction is
seen Lo incl'ease, and aftel' one clay the spicules become again high1y
refi-t"LCtive. If tbey are now as much as p08sible separated from
aClllel'ing glycerine anel iransfel'l'ed into glycerine of.n
1.4508, it
is seen that they c1isappear in t11is medium, anc1 conseqnently have
abs01'bec1 again theil' ol'iginnJ qnantity of \"later. SpienIes, whieh have
been dl'ied by P 2 0 G anel arEl exposed 10 the air aftel'wal'c1s, behave
in lhe same way. On 010 othcl' hand we have examined tIJe bebavi0111' of spiènl.es whieh, aftel' being isolated and \vashed, were noi
eh'ied in the air, bnt immediately aJter l'emoving thc adjacent water,
\VCre 1l10un(ecl in glycerine with n
1.4508. vVe conld jndccd sec
a vcr)' s1igh!, cliffel'enC'c wiih spicnies which had been dl'iec1 in lho
ail' at ::m ol'dinal')' wmpel'l1tl1l'e, morc than cOI'l'espoJlelcd with possibly
aclhCl'cn(, wat cr, bnt too small to be mcasl1l'ecl. HOW<WCI', il appeal's
that, eyen at the orclinal'y lempcl'l1tme, Ihc spicopnl givcs olf
some watcl'.
COllRcC(l!Cntlr we Jm"e demonsiraled thai IlJe spicopal is iJ, fOI'm of
hydl'l1ied si1iceons a('ic1, which ma,)' givc oir watel' in an almosphel'e,
dl'ied by P20", wInch climinishes hel'ehy Ül l'efl'i\.clivc index, antI
whieh may again absOl'h tIJe original qnanlilr of w[tICl' b~' immcI'sion
ill a watery solntion or by cxposllI'e 10 moisl air. The spicopalalso
behaves with l'cgal'd 1011Ie absol'ptive powcr fol' wal Cl' jllSL fLS a
gel, [ts has boen Rhown by Ihe weU known [tlHl intl'icale l'oseal'clws
=
=
=
of VAN Bl~l\Il\nn,l!;N.
(1'0 be continued).
I
I
- 15 -