NOTES ON THE PHYSIOLOGY OF SPONGES.
315
Notes on the Physiology of Sponges.
By G. P. BIDDER,Sc.D., F.L.S.
(With Text-figures.)
[Read 6th May, 1920.1
THEtwo preceding papers allucle to some questions in histology and physiology,
the further discussion of which seems better placed under a title where they
may be expected.
NOTEA.-Cercids (p. 301).
Minchin’s “ minute wandering cells ” (1897, p. 499) are clearly elements
of great interest and importance. As such it is convenient that they should
have a short and pronounceable name, and I propose the name “ cercids ” lrom
the Greek neppnlc ( K ~ ~ P K & x ) ,which in two of its nieanings well describes their
form ; the shape when the nucleus is in the middle sufficiently recalling that
of a ‘‘ shuttle *,” while the wedge-like shape manifested when tlie nucleus is
terminal may stand for the “ cuneus ” of Beats in a theatre or amphitheatre
(Pl. 24. fig. 7).
Minchin’s description of their origin and history in Clathrina coriacea
takes a diflerent aspect when, it] 1908 (p. 354, fig. 71), he draws them also in
Leucosolenia ; and again with my observation of them, recorded above, as
burvtiiig i n a swarm from the wall of C. (G.) coriacea. In Dendy’s careful
drawings (1914, pl. 24 and pl. 26) there are somewhat similarly shaped objects
shown in Grantia comnpressa : fig. 44 inside an ovum, fig. $0 in a problematical spherical enclosure.
But my cercids in 8.coriacea measured 4 p to 5 p long by 0.5 p wide, except
at the nucleus, which is 1p to 1.2 p in diameter. Minchin’s “minute
wandering cells,” in the same species, are in his figs. 17, 19 about 7 p long
with nucleus 1.4 p. Minchin’s “ minute amcebocytes )’ in Leucosolenia
measure 3 to 5 p x 1 to 1 . 5 ~(a nucleus is not shown) j while the objects
drawn by Dendy are only 2 p x 0.3 p with “ nucleus ” 0.6 p. I define the
name “ cercid ” as applying to the mobile and emigrant cells of G. coriacea,
leaving it t o the future to determine if truly homologous cells occur in
Leucosolenia and Grantia.
‘‘
* The first meaning given to K q d s by Liddell and Scott, following Smith’s Ant., is the
rod or comb by which the threads of tlie woof were driven home ”; but in this they are
wrong, and “ shuttle ” is the true meaning, on the authority of Butcher and Lang (Translation of Odyssey, V. e2); Lnng, Leaf, and Myers (Translation of Iliad, XXII. 448);
Edwmds (A Compnnion to Greek Studies, Cambridge, 1916, p. 620), Blumner (Gewerbe
und Kiinste, 1876, i. 134) ; and my friend Professor Henry Jackson, who told me of the
error, 1,. and S. give no Greek word for ‘(shuttle,” rightly ouitting T U V O C ~ O S given by
Smith.
316
DR.
a. P.
BIDDER : NOTES ON THE
The suggestion is strong that cercids, produced by the repeated division of
archsocytes, are in G. coriacea locomotor fertilizing elements which leave the
body and drift in the water, to enter eventually the oiicyte of another sponge.
Whether they first develop a flagellum, and whether they co-exist with or are
replaced by tho flagellate spermatozoa described (to the Linnean Society on
Dec. l l t h , 1919) by Dr. Gatenby in Grantia, or the gregarine-like objects
which T have figured (PI. 24. figs. 4, 5, 6) emerging from [or entering-Gee
Postscript, p. 3021 the cloaca1 wall of Sycon, it would as yet be futile to
disciiss.
[Sept. 20, 1920.-On the day that this MS. goes to press, I have a letter
from Mr. Julinn Huxley, containing akefches of small cells which he has discovered in the tissues of sponges. They have closely the appearmce of
Plate 24. fig. 7, and judgment on the function of cercids must be suspended
until his observations are available.]
NOTE
B.-Cessation of the Current (p. 301).
When the collar-cells are completely covered by a lining of invading
porocytes (see 1892 b, fig. 2 ; 1897, p. 487; 1900, fig. 42, F ; and 1908,
p. 326), there can be no current; and a iiiotile spermatozoon could enter by
the osculum in those species (as Ascaltis cerebrum and A. reticulum) in which
the latter cannot close. Assuming that it is to the granules of‘ the porocytes
that the Clathrinids owe their characteristic scent, the spermatozoa, after the
oscnlum is passed, will enter a highly odoriferous chainber, to the porocytelined walls of which they will be strongly attracted.
The current may also be completely stopped by the clogging of the pylocptes and, in Heterocoel sponges, by the choking of the afferent canals. I
have found this happen in ten minutes to Leucandra aspera fed with indigo,
and in half-an-hour, when fed with Indian ink, the current was very much
diminished ; sea-water, milk-white with starch, stopped the current in two
minutes. I n nature similar cessation must be at times caused by unusual
turbidity of the water.*
Outside these two cases, it may be assumed on purely general grounds that
pathological conditions may kill or paralyse the collar-cells, while leaving the
ova sttill suscept.ible of successful fertilisation. Thus, Annandale (1907,
* That such cessation is not due in Calcaronea to reflex closure of the pores, as stated by
Lendenfeld (of. 1896, p, 33), is proved by the fact that sections show the pylocytes widely
open and choked with starch grains (see nnte, p. 808, fig. F). Parker’s experiments
(1910 b) on StyZoteZZiz have led him to the same conclusion, nnd to a similar diRbelief in
Lendenfeld’s assertions.
The form of a pylocyte, viewed from one of the surfaces, is strongly suggestive of 8
sphincter, but I beliere this suggestion to be delusive. A pylocyte is a perforated cell whose
differentiation is to make intracellular communication between one cavity and mother ; it
in comparable to a cell in the channel of a nephridium, and not to a muscle-cell ; it is a radial
cell perforated radially, not a tangential fusiform cell whose ends are united, and the forces
exerted by the cell oppose those of surface-tension which would obliterate the lumen,
317
PHYSIOLOGY O F SPONGES.
p. 387) observed in India that Spongillu ceases its currents during the hot
hours of the day, the oscula aud poles retnaining open ; he deduces that the
flagellar motion tiiust have ceased. My experiments on tlie currents of
Calcaronea a t Naples do not show this, but the records show some evidence
of a possible reduction in power in the hottest hours. But, for the question
before us, it riso in temperature sufficient to paralyse the flagella of the collarcells might be expected also to suspend the rnoveriients of the spertnatozoa,
so that entrance tiy the osculuin would not then be effected.
I cannot find any satisfactory record of an observation showing with
certainty that in it sponge, with its apertures open ant1 i t s collar-cells
unchanged, motion of the flagella spontnrieouuly stops and begins again.
Such is certainly the impression gained on first experiments with living
sponges ; but a4 experionce m:ikes allowance for injury, temperature,
suffocation, obstruction by air-bubbles, etc., the impression steadily
diminishes. The r e d t of' rather prolonged work on the living collar-cells
(1895) wits to Inake me regard a iriotionless flagellum as a sign of death, or
danger of death, in the cell which bore it.
NOTEC.-On
Odour and flaxretory Granules (p. 299).
I n regard to the stronger and more pleasant odour possessed by Clatlirinids
as compared with Sycon, Grantia, etc., I am pleased to be corroborated 11y
my friend, Mr. L. R. Crawshay, who very kindly made observations on the
shore at Plymouth, collecting Clatlirina coriacea and Sycon separately in
stoppered bottles. His experience accorded with niy statement, though, the
season being mid-winter, the conditions were not very favourable.
There is evidence of a direct cliaracter that considerable difference exists
between these two groups in the nature of' the granules formed by the
porocytes and ectocytes. I found indigo-carmine deposited freely in the
ectocytal and porocytal granules of Clathrina clatlirw (1892 a), Guanclia
eoriacea, and Ascaltis (webrum and reticulum ; but never was able to
demonstrate del'osit with Sycon raphanus, Leucandra aspera, or Gruntia
compressa : and Cotte (1903, p. 459) also obtained negative results with
Sycon raphanus. The facts suggest a modification of my views as to excretion
(1892 6, compare Urban 1903 and Minchin 1908)". That is to say, it
appears logically possible that these refractive lipoid granules, of which I
have recorded (1. c.) niany puzzling reactions, are not in all sponges formed
by a process which also secretes sulphindigotate of soda; but that in the
Calcineti (and possibly at sexual times in &con) an odoriferous body is added
which is so formed.
Cotte has a very interesting observatiun (1. c. p. 528), that the individuals
of Sycon raphanus, which were " exceptionellement riches en pigiiient jaune
* See also footnote, p. 323.
LI".
JOURN.-ZOOLO@Y,
VOL. XXXIV.
24
318
DR. a; P. BIDDER: NOTES ON THE
Explanatam of Text$gtres.
All figures are approximately x 1660 (the scale of Dendy’s 1914 plates).
Figs. 1 A, B, 0 are from Grantia compressa, fig. 1 D S.raphanue.
Fig. 1 .4. Collar-cells from a sponge gathered at low tide, 27 hours out of the water and
replaced in sea-water for 19 hours, flagella moving rapidly. A t f a small ortion
is drawn of one of the aggregates of excreta which were in t h o chambers. (8eb. 7.)
Note that after their long purging and deprivation of food the collar-cells show
perfectly trans arent spherulea or vacuoles and protoplasm in place of the
greenish spher$es and granular protoplasm of normal health. Note also that
the nuclei are not pear-shaped as deecribed by Minchin, but s herical 8s I have
always found them in life, except that occasionally they are elEpsoida1 owing to
constriction by the cell-wall in suffocation (see 1896, 23, rediscovered by Cotta,
1902, see 1903, p. 463). Progressive suffocation is s!own in Fig. 1, B.
Fig. 1B. a, b, c! d, e. Five successive sketches drawn from the same cell, showing E.
moving lobule of fsjces in a position which must be just under the iris-menbrane. %rom a s onge 24 hours exposed by the low tide, 2 hours in sea-water
after gathering. k*ella very active. (Jan. 8.)
Fig. 1 C. Living collar-cells, showing faxes in a similar position, From a normal sponge.
Basal spherules (shaded)are greenish. In the right-hand cell the spherical dotted
globule was brown*. (Jan. 20.)
Fig. 1D. Ammbocyte with vesiaular nuclei and enclosing a ball offeces, projecting between
two collar-cells into the chamber. From 8. raphnnua, fed with carmine 20
minutes, 18 lours’ rest, killed osmic acid, decalcified formic acid, not otherwise
stained.
.
*
Comparison with observations made at Plymouth since this paper was written show8
that the brown globule was clearly a Syncryptu.
319
PHYSIOLOGY O F SPONGES.
d’or, e’taient en &at d’e’laboration sexuelle t r h active (mois de Janvier) .” I n
the 8ycon raphanus of the aquarium, with which I mostly worked, I never
remember seeing any golden-yellow pigment, so that I am unable to do more
than transcribe the passage.
NOTED.-The
Fmes of Sponges, and Phagocytosis (pp. 306, 310).
The fact that Dendy occasionally found in inhalant canals the “small
masses of granules” which he describes and figures (1914, p. 365, fig. 93)
does not discredit my interpretation of them (1895, p. 18, fig. 13a ) ns being
feces. I t is obvions that, even in the sea, the faces of’ another sponge may
often drift into the afferent system; but the sponge from which Dendy drew
his fig. 93 was examined two or three hours after it was collected, and was
watched in a glass dish where ‘(there was an active current issuing from the
vent, bringing with it a quantity of fine ~-ellowish-grey sediment, which
collected at the bottom of the glass dish” (1914, p. 320). I n that ~ r n a l l
volume of water any particles carried out in the osculnr stream, which were
too small or light to sink rapidly, would be borne again back into the sponge
through the inhalant canals.
That they are not spermatozoa is proved by my finding them in the three
winter months, t o which that part of my work on the living Grantia
compressa was limited. 1 found (1895, p. 11)that this sponge is annual at
Plymouth, larve being recorded in May and July, and only the young sponges
produced by thein being found in September, when there are none but minute
individuals. Deiidy rediscovered this, and considers that the breeding-season
‘‘ would seem to begin in the first, half of April,” when “ comparatively few
embryos are found” (1914, p. 321), his visit to Plymouth being April 10th
to April 22nd. My friend Professor Dendy will therefore agree with me
that a drawing (1895, fig. 13 a) made on Feb. 7th was not from a hiige swarm
of spermatozoa, and my first observation of these fBcal agglomerations was
in December. [For breeding-time see also Orton (1920) pp. 340, 341.1
These extremely large inasses were met with in sponges which had been
subjected to experiment in regard to their endurance of low-tide conditions,
and it is worth remark that the sponge from which Dendy’s fig. 9 3 was drawn
had been gathered about mid-day April Mth, 1912 (1914, p. 320), and
therefore a t dead low-tide, the day before an exceptionally deep spring-tide.
It is obvious that in sponges which have been out of the water for many
hours the cellular excreta from the collar-cells, if there be such excreta,
must accumulate for all those hours in the flagellate chambers, instead of
being steadily thrown out in the normal way through the oscular stream as
described by Bowerhank (1858, p. 121)” and others. There is, hherefore,
prima facie reason for supposing that any finely granular substance found to
* Compare also 1857, last paragraph but one (p. 15 of the reprint) :-((If the sponge ”
some time after feeding with indigo “ b e now removed into fresh water, the ejection of
molecules of indigo continoes for hours to bo slowly effected.”
24*
320
DR.
a.
P. BIDDER: NOTES ON THE
accumulate in tho chambers under these conditions is composed of such
cellular excreta. And, asVosmaer and Pekelharing point, out (1898 h, 1). lo),
the ‘‘ clods of detritus” are many tinies larger th:ui tlie prosopyles, and
conscquently could not have entered through the prosopyles, but must
necessarily have been formed within the chambers.
Add that, in such sponges, I found in life that “ almost every cell po.;sessed
a globule containing angular dark particles,” sonietimes, as in (1895) fig. 4,
“ projecting on the surface between collar and flagellum.
These globules
were observed and drawn moving in the distal protoplasm of the cells ;”
(Note G) “tliere were numerous bodios of similar uppearannoe (65 fig. 13a )
floating freely in the cliamber ” (1 895, p. 18). The figures illustrating this
statement lost detail in their reproduction ; those appended here are on the
full scale of the sketches (fig. B enlarged to the scale of figs. A and C).
They are corroborated by Cotto’s ohservation (1903, p. 559), in ti Sycon
raplianus which had absorbed tournrso1;of two blue spherules (ench containing
a darker blue point) being ejected by choanocytes; the spherules being
thrown out froiii the annular space between flagellurn and collar.
I n regard to the gelatinous matrix of the faces, “ I have often suspected,
from paraffin sections, that the food vacuoles of sponges are filled with some
gelatinous imitter, coagulated in preservation ” j l 8 9 5 , p 18). C‘otte (Z.C.), in
Reniera simulans fed with carmine or lamp-black and returned to clean water,
observed afterwards “ des b o l ~fdcaux ” in the tl:igellate chambers. ‘‘ L a
substance hyaline qui agglutine les corpuscnles solides intliquc, vraiseniblablement qu’il y a eu ingestion pr6alable par les clioaiiocytes, e t que Ics
choanocytes les ont ensuite iihandonn6s.” Greenwood and Saunders (1 894,
p. 449) describe a type of digestion in Myxoinycetes where ‘‘ any nodule of
food as yet unclianged is invested by a homogeneous mucilaginous spliwe, or
in later stages . . . a viscid mould or cast of the interior of the vacuole
is formed” . . “ W e think that Rome element present is not only undissolved but insoluble, and comparable prob;hl,v to that nincilaginous
residue which gives so distinctive an appearance to the egesta of’ many
Infusoria.” Discussion with Miss Greenwood greatly influenced my conclusions.
It is interesting that Dendp’s description, quoted above, verifies the old
observation of Carter (1849, p. 98) that the “ fmcal matter ’’ issuing in the
owular current is markedly lieavier than water. It has becn suggested to
me by a friend that this may indicate the deposit of c:ilcium salts in the
faecal boli, and that to these may be in part diie the refractive or opaque
granules which chsracterise the boli. I n any case, I venture here t o repeat
from mother standpoint the comparison which Dendy made between these
cellular faces in the flagellate chiimbers and the “ masses of granules ”
figured as spnrinatozoon-heads by Poldjneff and other authors. If’ tlie sign
of completed digestion in the collar-call be the coinplete replacement of the
.
..
PHYSIOLOGY OF SPONGES.
321
food-vacuole’s contents by a pellet of gelatinous matter containing refractive
or opaque granules, thig is likely to be also the process of digestion in a
mesogloeal phagocyte *. Tha evidence is that the “ ninsses of granules”
are the last products of digestion, antl within :i phagocyte, or group of
pli:igocytes, may be taken as sliowing where the combat Nith an intruding
organism has been victorious aiid complete.
This speculation has partly originated in tho attempt to explain the cell
drawn in fig. D, alluded to at the meeting of the Linnean Society on Dec. 11th.
W i t h a superficial reseinblsnce to a I)ylocyte, it differs in its thick body and
large vesicular nucleus ; in each of these particulars it resenil)les Dendy’s
fig. 81. Also the plnne of its cresceiit is radial instead of tangential to
the chamber into which it projects, instead of framing an aperture in tho
wall.
The appearance of the ceIl, either in fig. 1 D or in Dendy’s fig. 81, is
unquestionably that of a goiiocyte. I n describing my feuding experiments,
and confirming my previous observatioiis that tlie gonocytes feed on the basal
spherules of the collar-cells, which are stores of digested food (1892 b, p. 471;
quoted 1893, p. 220 ; rediscovered 1914, pp. 328, 344), 1 wrote :-“ A large
number of gonocytes are in contact \\ ith collar-cells which contain plehtiful
carmilie ; in only two of thein I f o u n ~ lcarmine-grains, and it is tempting to
deduce that vacuoles aiid undigested food d o not !)ass into the goiiocyte ”
(1895, 1). 30). (lotte (1903, p. 448) uses siinilar language :-“ Les coupes
de L$jcanJru niontrent quelques grains de carinin ou de cliarbon englob& par
de3 amibocytes ; c’est I&, on peut le dire, une v8ritalJIe exception.” But our
experitiients show only that the mncebocytes of Calcaronea do not ingeet
particles which reach the cboanocgtes froin tlie water of the chamber. ‘I‘liis
negatives iu no way their power to engulf foreign bodies \\liicli they may
find iii the Inesog~cea. And beside the classical experiments of Metschnikoff
(1879), Cotte has shown that they have this power in 1Ceriie.r.a (p. 448) and
Spongelia (p. 455); while Dendy (1914) has given a most interesting
description of phagocytosis bj- oocytes ant1 other amoebocytes in Grantia
conzpressa.
I interpet fig. 1D as an amoebocyte which has digested tioine foreign
subdance encountered in the mesoglcea, antl is dragging the excreta to be
cast out into the efferent water of the flagellate c1i;lniler t. And Dendy’s
fig. 81 indicates that the substance partially digested there, vlio11y digcstetl
in my fig. 1D, i a a lightly-staining sphere of 6 diameter (with nine spots,
* [Since this paper was read I Lave seen van Tiigt’s interestins work (1919, p. 162), in
which he records similar faxes formed by the wiiiaeboid cells of S’onyilla aiid by the walls of
the efferent canals.
Van Trigt conaiders that this sponge feeds upon and digests the cells of the green alga
which gil e its colour.]
t [Cy. van Trigt, 1. c.]
322
DR. ct. P. BIDDER: NOTES ON THE
staining more darkly, in fig. 81). The indications seem to me that these
figures, Dendy’s fig. 85, and many o t h m in his very interesting plates-all
record stages in the war against ,Synarypta, which appears to be carried on
successfully in Grantia either by thc gonocytes themselves, or by other
amcebocytes which have this function *.
Most interesting in this connection is Polbjaeff’s statewent (1854, p. 72) as
t o sperinospores ” in Verangia :-“ When ripe they recall so vividly the
corresponding formations in Sycon raphanu8 (with the sole distinction that
while in this latter instslice the nucleus of the covering cell in quite ripe
spermospores is in most cnses indistinct, in Verongia I find quite cmpty
capsules, nevertheless, provided with it).”
All the covering cell3 ” represented in Veronyia (pl. 10) contain only
masses of granules ; and similar inasses are in Curtmiospongia in an
endothelial chamber, as described by Schulze (and verified by Polbjaeff) for
Oscarella, Aplysilla, etc. I snggest that the nucleus of the ‘I covering cell ”
is indistinct where the contained Syncrypta has killed the amcebocyte which
ingested it, and that those in Kero,igia are the nuclei of amcabocytes which
-as shown by their granular contents (as in iny fig. 4)-liave destroyed the
Synciypta, themselves uninjured. An endothelial capsule occura in Carteriospon.qia, instead of a covering cell as in Veronyia, because the heap of
granules is 40 p x 15 p instead of 9 p in diameter, showing that the
digested substance w a s too large for one phagocyte to contain. Such
conclusions merely assixme a process wholly comparable with the destrnction
of Oscillatoria by the amcabocytes of Spongelia which is described by C‘otte
(1. c. pi 455).
As Vosmaer said (1837, p. 412) :--‘The strustures which many spongologists have set forth more or less positively as spermatozoids may have
been so or may not; in many cases it remains doubtful.’
‘(
‘(
NOTEE.-Origin
of Sponges.
If the hypothesis be adopted that the granules of porooytes attract
spermatozoa, a possible history OE the origin of sponges is suggested.
If we construct our imaginary ancestral sponge on the lines of the Sycon
amphiblastula, illumined by Protospongia, we find a colony of flagellate
collared cells who;ie function is to obtain nourishment, surrounded by their
associate archaocytes, which receive the digested nourishment and alike
* I am unaware how far, by those who have worked at these problems, phagocytosis and
conjugation are considered cognate or opposite. M y friend Miss F,. R. Saunders tells me
that in the revival of plasmodium of Myxomycetes from the sclerotial condition, a8 each
sclerotial cyst is enveloped by the advancing plasmodium, it is uncertain for a moment
whether a vacuole will be formed round its protoplasm and this be digested, or whether it
wilI ievive rapidly enough to burst to the moisture, and unite alive with the syncytinm.
This alternative absorption as food, or as a living partner, suggests that conjugation uay arise
from attempted phagocytosis.
PHYSIOLOGY OF SPONGES.
323
excrete in a manner possibly protective for the colony * aud are charged with
its reprodnction.
At this stage we may conceive the secretion of a n attractive odour to have
become permanentlv associated with their nitrogenous excretion, with the
advantage of more frequent reinvigoration of the stock by conjugation with
locomotor units from other colonies.
Development led to differentiation of purely reproductive cells froin those
charged with excretion, the reproductive cells being placed in greater safety
by a covering of the excretory cells. The latter would still attract the
locomotor units, which, when engulfed, they would pass on for nuclear union
with the gonocytos. This absorption from the exterior and transmissiorl to
the interior would be simplified (as the reverse process has probably been in
nephridial tubes) to perforation (qf. 1892, p. 182). Misdirected perforation,
placing the excretory sirrface of the sponge in communication with the
flagellar surface instead of with an oocyte, would sporadically occur, and
when so occurring would lead to n sudden increase in the hydraulic efficiency
of the flagella as a food-catching apparatus, supplies being thus brought to
centrally placed choanocytes which otherwise could only be reached by water
which had passed over their neighbours. Such misdirected perforation would
therefore be perpetuated by the increased prosperity of those colonies in
which it happened, their form being now in essence that of the rudimentary
Olynthus ; from this upwards “ all transition from more to less primitive
canal systems exhibits a n increase in the ratio” that determines the
mechanical efficiency of the canal system (1888 ; 1895, p. 29).
The cercids are fragmented archeocytes (see Minchin 1897, p. 500) which
ant^, p. 300) break out into the surrounding water and effect conjugation
with the archaeocytes of other colonies.
My excuse for printing such a fanciful story is the extreme difficulty of
forming any conjecture as to possible value to the organism of the intermediate
stages in the evolution of a hydraulic system supplied by intracellular pores
(f. MacBride, 1918, p. 52). If the pores were multicellular, we might
conceive them as originating as grooves or furrows in the flagellate surface,
with the advantage in every stage of bringing better supply to the more
central flagella. Such an ovolution would fit in with many embryological
observations, and there is so much evidence that sponges are polyphyletic
that it is not impossible that both developments have occurred?. B u t
in both Calcinea and Calcaronea we know that the pores are intracellular.
* The nitrogenous excretion of the archteocytes may be beneficial to the colony by heing
either repulsive to foes or attractive to friends. But, in view of the known defscation by
collared cells, these probably get rid of their own nitrogeuous poisons, and I do not now
believe that in this sense either the primitive archaeocytes or the specialised porocytes excrete
for the whole colony. Loisel’s criticism on this point (1898, p. 203) is quite just.
t In the Donatiidae and the Hexactinellida there is no evidence of the presence of porecells, and it is doubtful if in either of these groups there is any sexual reproduction.
324
DR. G . P. BIDDER: NOTES O N THE
Minchin (1900, p. 49) suggests that the pore-cells may primarily be
nutritively phagocytic in function, and therefore have coine to surround
pre-existing afferent pores. The hypothesis does not seem (I prior; persuasive; and it does not fit well with the facts, since we have no evidence
of pre-existing pores, nor, in these sponges, of any prosopyles which do not
perforate porocytes *.
[POSTSCRIPT.
NOTEF.- Osgenesis in Sycon.
Dendy’s derivation of the oocytes from collar-cells (1914) in Grantia
compressa is not in h:rrmony with my own views ; but on re-examination of
my preparations I cannot claim that they disprove it.
His figs. 2, 3, 12, 13, 14 (as also 62, 66, and 68) are from a sponge which
had been a week in the aquarium circulation. I t appears possible, therefore,
that he observed the early stage of the pathological changes in the flagellate
chambers, of which I have recorded the condition after a month in the
aquarium (1895, p. 27). I t is remarkable, however, that in my pathological
specimen, though the highly gelatinous mesoglcea contains many cells of the
size and appearance of collar-cells, there are scarcely any recognisable
gonocytes or cells which resemble gonocytes in size or character.
I agree with Dendy that the ova are fonnd free i n the cavity of the
chambers, strange as this appears, and that such is the interpretation of the
“ laiger iiucleate cells, possibly Protozoa, partly enveloped by the distended
collars, sometimes more than one cell converging on theni,” which I described
in 1895 (p. 31), and which are well indicated in his figs. 11 and 74 (in the
latter case the ovum is called a ‘‘ primary spermatogonium ”). I found
in sections of S. raphanus unmistnkahle ova in the lumen of tho flagellate
chambrr and one just passing through the wall, and I sketched a t Plymouth
(April 1920) such an ovum alive in the cavity of a flagellate chamber of
G. compressa, seated with psendopodia stretching over the free ends of halfa-dozen collar-cells, in outline ludicrously like an octopus. Between the
vesicular nucleus and the free ovoid surface was a comet-shaped streak
or arc of minute green fragments, suggesting that it had used its freedom to
feed on and digest an alga, thus supporting Dendy’s suggestion on pp. 323,
335 (1914).
NOTE(3.-Migration
of the Nucleus i n Collar-cells.
I n fig. I C the nucleus is visible in two cells, and is men to have moved
downwards to allow of the escape of the faces through the aperture in the
* Cotte (1903, p. 434) considers that there is a general power of cell-perforation in the
piaacocytes of Renieru, nnd quotes Topsent for similar perfora.tions of’the contractile cells of
this specie8 and of Cliona.
PHYSIOLOGY OF SPONQES.
325
iris. Such displacement miist also occur when any large niass of food is
ingested, and Syncrypta spheres cotiiinonly do not pass the nucleus (qf. fig. a).
Hence, Hammer (1908) found the nucleus often not distal, and his fig. 85
shows such a nucleus, w i t h the agglomeration of ingested foreign bodies
which have forced it donn. H e correctly quotcs me iis having watched
the living nucleus iiioviug in the protoplasin, biit I found its coninion situation
apical. The fact that his observation of a usually basal position in life
was contradicted by his stained sections indicates that in the living cell a
food-vacuole was mistaken for the nucleus-in like mariner as I described
the nucleus a t first as a vacuole (1895, p. la).]
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