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HARVARD UNIVERSITY
eh
IAS
LIBRARY
MUSEUM OF COMPARATIVE ZOOLOGY
ect
QUARTERLY JOURNAL
OF
MICROSCOPICAL SCIENCE
EDITED BY
EH. RAY LANKESTER, M.A., F.R.S., F.LS.,
Fellow of Exeter College, Oxford, and Professor of Zoology and Comparative
Anatomy in University College, London ;
WITH THE CO-OPERATION OF
Poe BALFOUR,. L.L.D., F.R.S., F.L.S.,
Fellow and Lecturer of Trinity College, Cambridge ;
W. T. THISELTON DYER, M.A., F.R.S., F.LS.,
Assistant Director of the Royal Gardens, Kew ;
AND
E. KLEIN, M.D., F.RB.S.,
Lecturer on Histology in St. Bartholomew's Hospital Medical School, London.
VOLUME XXI.—New Szrizs.
With Lithographic Plates and Engrabings on Wood.
LONDON:
J. & A. CHURCHILL, NEW BURLINGTON STREET.
c 1881,
‘ _ ‘ .
i 1S cr i ut E eget, cae
um Saunt hi pagar a
oes 5 A . eae
Re senten e n- Smitt’s
Specimens were procured from Wijde Bay, Spitzbergen.
On the 30th January, 1873, on the “ Challenger” Expedition,
a specimen of large size, of a form very closely allied to if not
identical with one of those described by Koren and Daniels-
sen, was described and figured by Sir C. W. Thomson,‘
under the name of Naresia cyathus. This specimen was
procured in the North Atlantic in lat. 36° 23’ N., long. 11°
18’ W., from a depth of 1525 fathoms. A second ‘specimen
of the same form, but of smaller size, was procured on the
2nd March, 1876, in lat. 36° 44’ S., and long. 46° 16’ W.,
from a depth of 2650 fathoms. Other specimens of a closely
1 © Forhandl. i Videnskabsselskabet i Christiania,’ 1867, p. 23.
2 * Fauna littoralis Norvegie,’ part iii, 1877, p. 104, pl. iii, figs. 12—14;
pl. xii, figs. 4—14. i
* “ Kritisk forteckning 6fver Skandin. Hafs-Bryozoer,” in ‘ Ofversight af
Kongl. Vetensk.-Akademiens Handlingar,’ May, 1867, pp. 292 and 353, pl.
xix, figs. 283—31.
* “Nature,’ i, p. 387.
VOL, XXI.—NEW SER. A
2 GEORGE BUSsK,
allied but quite distinct form were obtained on the 10th
September, 1875, in lat. 9° 5’—10’ 8., long. 30° 49’—53’ W.,
from a depth of from 32 to 400 fathoms ; and again, on the
14th December, 1875, in lat. 33° 31’ S., long. 74° 43’ W.,
from a depth of 2160 fathoms.
These different forms constitute certainly three and, as I
am inclined to think, four distinct and well-characterised
species ; but they all agree in certain very peculiar characters,
which would seem to be almost, if not quite, sufficient to
render the group composed of them of generic value, or, at
any rate, to rank as a distinct sub-genus of Bugula.
To this genus or sub-genus the appellation bestowed upon
it by Koren and Danielssen obviously has priority over
Naresia.
The species belonging to this group at present known
are :
1. Bugula (Kinetoskias) Smittii, Dan.; Kinetoskias Snutti,
Kor. and Dan., 1. ¢.; Bugula Smitti, Sars.
2. B. (Kinetoshias) arborescens, Daniells.; Ktnetoskias
arborescens, Kor. and Dan., 1. c.; Bugula umbella, Smitt,
Ge
3. B. (Kinetoskias) cyathus, W. T.; Naresia cyathus,
C. W. T.,1.¢.; ? Kinetoskias Smuttic, K. and D., 1. c.
4, B.(Kinetoskias) pocillum, n. sp., mihi.
1. A. Smitidz is thus characterised by Koren and Daniels-
sen.
“Zoarium umbellate, with four strong main branches
springing from a stem about 150 mm. (6 inches) in length,
which is cylindrical, naked, and completely pellucid, and gra-
dually thickened towards the lower end, from which numerous
yadieal fibres proceed, by which the growth is affixed to
small stones or sand. The branches are biserial, and divide
several times dichotomously. The zoecia are about 0°S mm.
(0:03 inches) long, with a breadth of 0°31 mm, above, and
ef 0:13 mm. below. In shape they are elongated and
tapering below, truncate above. The posterior surface
is striated transversely towards the lower part. A short
spine is placed on the upper and outer angle. On the upper
and anterior border of the zowciwm there is a blunt, solid,
horny, conical process, which appears to serve as the point
of insertion of a strong muscle, which expands on the
anterior surface of the superjacent zowciuwm. This musele is
attached to the conical process by a tendon.”
“Phe avicularia are placed on the outer border of the
zocecta, a little above the middle. They are of an elongated
form, with a rather long mandible curved at the point. The
NOTES ON A PECULIAR FORM OF POLYZOA, 3
ocecium is sub-globular and affixed to the upper and outer
border of the zocecium, arching, as it were, over the
aperture.”
The anterior muscle above mentioned is described as lying
between a fine exterior membrane and the proper ectocyst.
This membrane, again, is said to pass down from one
zocecium to another, and as connecting the branches together,
being finally continued into the stem.
Amongst other particulars, the authors state that the ovary
is attached to the endocyst on the upper and anterior part
of the surface of the zocecium, consisting of an agglomeration
of cells wherein the ova are developed. The testis, on the
other hand, they state, is situated at the bottom of the
zoccium, and is formed of similar cells to those forming the
ovary, but filled with spermatozoa.
Kinetoskias, therefore, is regarded by them as a complete
hermaphrodite.
The incurvation of the branches of the zoartwm towards
their termination is ascribed to the action of the anterior
muscles above noticed. There is, they observe, no common
colonial muscular system.
2. Kinetoskias arborescens is described as having a
flexible zoarium, supported on a very short stem, from
which radiate four large main branches which sub-divide
dichotomously. The zoccia, which are biserial and alternate,
are 0°58 mm. long by 0°31 broad above, and 0°18 mm.
below. They are of a narrow form, and nearly pointed
below, especially when viewed from behind ; above they are
broad and rounded, the upper border being oblique in a
direction from within upwards and outwards, so that the
upper and inner angle is rounded off, and the outer rendered
more acute ; there is no spine on this angle. From the
middle of the upper convex border of the zocecium nearer the
anterior margin is a strong, horny, obtuse conical process
or apophysis, which is said to give attachment to a muscle,
which, as in A. Smittiz, is described as spreading out over
the anterior surface of the superjacent zocecium.
The anterior surface is said to be covered with scattered
calcareous granules, and the posterior surface, which is very
convex, is strongly striated transversely. The striz or
ruge are elevated and oblique from below upwards and
inwards.
The avicularia are placed on the upper and outer angle
of the zoecia. They have the form of an eagle’s head, and
are supported on a short articulated stem. No occia were
observed,
4, GEORGE BUSK.
Professor Smitt, in his independent account of the latter
of the two species described by Koren and Danielssen,
remarks that the zocecia are widely distinguished by their
form from those of other species of Bugula, inasmuch as
the lower tubular portion is entirely wanting, as viewed in
front, the membranous aperture occupying the entire ante-
rior face. The aperture is wider above than below, so that
the zocecium, he observes, has more or less of a boat shape,
as in Beania. But the Bugula type is nevertheless evidenced
in the incurvation of the inner border, whilst the lower
border of the aperture is straight. The upper and inner
angle is rounded off, and the outer more acute. The avicu-
laria are placed high up on the upper and outer angle of the
zocecium, and assume the same position, he says, as in
B. avicularia, though rather more pointed upwards.
On the dorsal aspect the zocecia present a still greater
peculiarity. In this aspect they are flatly convex, with the
outer border acute and the inner more rounded.
The surface, as in tea anguina, is traversed by raised
granular lines or ridges, which curve obliquely upwards and
inwards.
The lowest portion of the zocecium, which is in other species
of Bugula more or less tubular, is in this case simply con-
stricted, so as to constitute a laterally compressed peduncle,
placed somewhat external to the middle line of the
zocecium.
Close to this constricted part, and near the inferior and
outer angle of the zoecium, the radical tubes arise, the some-
what dilated commencement of which completely fills up
the space between the summit of the inferior or older
zocecium, and the base of the superior or younger, being
wedged in, as it were, between the two. From this point
a radical tube grows downwards, running along the outer
border of the lower zocecium, near the bottom of which
it unites with a similar radical tube arising from that
zocecium. .
Sometimes, however, he observes this conjunction does
not take place, but the two (or more) tubes are continued
side by side. But, generally speaking, as they descend all
distinction between the tubes disappears, their lumina
appearing to run together, so as to form a broad expansion,
which fills up the angular space between two contiguous
branches of the zoarium, stretching across from one to the
other.
Professor Smitt also states that in the interior of this
expansion numerous colonial nerve filaments may be seen,
NOTES ON A PECU@LIAR FORM OF POLYZOA, 5
besides which are only some free nucleiform particles
(fettkropskulor).
It is not clear, in Professor Smitt’s description, whether
the specimen of Bugula umbella, from which it was drawn,
had or had not a simple peduncle. But, so far as my
imperfect knowledge of Swedish enables me to say, I should
gather that he thinks it possible that the growth may be
more or less detached or free, the radical fibres only pene-
trating the loose muddy bottom without, as in most other
cases in the Polyzoa, the fibres being attached to any fixed
object.
The above brief summary comprises, I believe, the main
points hitherto made known with regard to the structural
peculiarities of Ainetoskias. My object in the present com-
munication is to show how far the accounts given by the
eminent and excellent observers above cited are in accord
with what I conceive, from direct observation of two closely
allied forms, to be the actual conditions.
The two forms that have come under my own observa-
tion from the “ Challenger” collection are:
1. Kinetoskias cyathus, C. W. T., and
2, Kinetoskias pocillum, n. sp. (fig. 3).
1. B. cyathus.—The general aspect and dimensions of this
remarkable and beautiful form are well shown in Sir C. W.
Thomson’s account of it,! and to which, so far as external
characters go, I have but very little to add. The zoarium
consists of an elegant infundibuliform, vase-like expansion,
constituted of numerous, long, sparsely dichotomising,
biserial branches, springing from an apical point at the bottom,
and curving gently outwards till, towards the extremities,
they are curled round upon themselves, the anterior aspect
of the zoccia looking outwards. This infundibuliform por-
tion of the zoarium is supported on a point, a little to one side
of the actual apex, upon the summit of a terete peduncle,
about four or five inches in height, and from about half an
inch in diameter at the bottom, tapering to a diameter of less
than the one tenth of an inch at the summit. At the lower part
of the vase-like cup the branches, to a height of about an
inch, are united, like the ribs of an umbrella, by a delicate
transparent membrane, stretching acrossfrom one to the other.
This membranous cup is brought toa point at bottom, a little
to one side of the spot from which the branches diverge, and
it appears to be quite closed, a very tight constriction exist-
ing at its junction with the peduncle. The latter, though
LL, ¢
6 GEORGE BUSK.
flattened in the spirit specimen, is, in the natural condition,
cylindrical, and probably, when distended, sufficiently stiff
to support the upper portion in an upright position, whose
weight, of course, must be very littlein the water. The wall
of the peduncle, though perhaps rather thicker than the web,
is perfectly transparent, and, so far as I can make out, quite
homogeneous; and in the interior, in the spirit specimen,
nothing is to be seen except a few minute nuclei and slender
branching threads, probably belonging to an extremely
delicate endosarc, and which it is allowable to suppose may
represent the so-called “colonial nervous system,” seen by
Smitt in the radical tubes of his B. wmbella.
The zocecia are about 0:045 inch long by 0°02 in width,
which is tolerably uniform from top to bottom. The outer
border, as in most species of Bugula, is hollowed on the ex-
ternal border and towards the lower end in most of the
zocecia, a sort of step is thrown out (Pl. I, fig. 1), upon
which is articulated the avicularium. The inner border is
evenly rounded, and the upper and inner angle is completely
rounded off, whilst the external is produced and crowned
with a short, pointed, spinous process.
Viewed behind, the zocecium is convex and the surface
perfectly smooth, without a vestige of any transverse ridges.
The outline is much the same as in front, and the outer
border is acute, the inner rounded. At bottom the zoccium
is seen to arise from the back of the subjacent one by a con-
stricted neck, on the outer side of which there is a chitinous,
thickened, ring-shaped process, which appears to represent
the spot from which, in the lower part of the branches, the
radical tubes spring; and the insertion of the zoccium
appears to be also surrounded with a rather thick, chitinous
ring. The oecia are of large size, attached to the middle of
the summit of the zocecium in front, and projecting forwards
in the form of a wide shallow hood.
The avicularia are about 0°02 inch long and about 0°006
wide. The mandible is about 0°01 inch in length, and
much curved; within it presents the usual arrangement of
muscles, and a thickened, glandular, (?) digitiform sac or
pouch.
Within the zocecium a rather large polypide is lodged, of
the usual conformation and muscular connections, and
having about twenty-four or twenty-six tentacles. So far
there is nothing very remarkable: but other peculiarities
remain to be mentioned, possessed in common by this and
the other species of Ainetoskias. These are—1l. The ex-
istence of a distinct muscle, which, arising from the front of
NOTES ON A PECULIAR FORM OF POLYZOA. 7
the base of the zocecium passes obliquely backwards and
upwards, expanding in a fan-shaped manner, to be inserted
into its hinder wall to the height of about one third or one
fourth of the zocecium (fig. 1a). The action of this muscle
must be to draw the entire zocecium downwards and for-
wards, or, in other words, to bend it on itself, and thus, by
the conctitrent action in many zocecia, to curl the branches
forwards ; an action that has, in fact, been noticed by Koren
aiid Danielssen in the living condition. Besides this flexor
muscle in A. cyathus there is an additional, smaller, fan-
shaped bundle of fibres, for the purpose, apparently, of
curving the step-like process of the wall of the zowecium, upon
which the avicularium is fixed, forwards, so as to causé the
avicularium to come in front of the zowcium (fig. 1c), which
appeais in the spirit specimen to be its usual position. I
have been unable to discern aiiything like ovary or testis
within the zocecia; but many, if not most, of the ovcia
are filled with an apparently vitelline mass or ovum of large
size.
Koren and Danielssen are inclined to consider that their
Kinetoskias Smitit is identical with Naresia cyathus of
Wyville Thomson; but, so far as Iam able to judge, from
their detailed description and figures, I do not see how this
can well be. The form and size of the zocecia and of the
avicularium and ovcia undoubtedly appear to correspond
with those of B. cyathus; but the general aspect of the
zoaritim it the two cases is utterly dissimilar. In this par-
ticular, however, it must be remarked that the natural-size
figure given if pl. iii! does not at all correspond with the
description in the text. 2. In A. cyathus there are no traiis-
verse ruge@ on the back of the zoweva. 3. The avicularium
is attached in B. Smti above the middle of the otiter
border of the zocecitm, whilst in A. cyathus it arises from a
distinct step-like process, quite at the bottom.
On these grounds there does not appear to me sufiicieiit
reason to regard Kinetoshias Smittu and Naresia cyathus as
specifically the same.
2. Kinetoskias pocillum.Though very tiuch smaller than
K. cyathus, the structure of the zoatiuin is exactly the sariie.
Like that species it consists of a vasifoii iifundibuliform
expansion composed of branches springing from a common
point, and, as in that form, united at their base by a trans-
parent membrane, which is coiiiiected with an equally trans-
parent, terete, iémbranous stem; about ore and a half to
two inches high, which, as in A. cyathis, tevminates inferiorly
OH, ¢:
8 GEORGE BUSK,
in a thick tuft of very fine tubules or hollow fibres, each of
which is individually affixed to an empty glodigerina shell, or
to some other Foraminifer. And there is the same complete
constriction between the stem and the membranous expan-
sion forming the bottom of the infundibular cup. The zocecia
differ from those of A. cyathus in having no spine on the
upper and outer angle, and in having the avicularium
attached by a distinctly articulated peduncle to the outer
border rather above the middle and without any project-
ing process for its reception. Posteriorly, the zoewcia are
irregularly oblong, the outer border being sharp and nearly
straight, and the inner as it were gibbous. The surface, as
in K. cyathus,is perfectly even and smooth, and very convex.
In many of the zoccia, more especially towards the lower
end of the branches, a small tubercular projection rises from
the upper border of the zowciwm (fig. 2) in the middle,
which would seem to correspond to the “horny conical
process” in the same situation noticed by Koren and
Danielssen, and supposed by them to serve for the attach-
ment of a muscle; but it is clearly nothing of the kind,
and, aS it seems to me, merely a rudimentary oecium. In
EK. pocillum these organs are much smaller than in &.
cyathus, but, as in that species, cucullate in form. They
differ, however, very markedly in the direction in which the
opening looks, which, in A. cyathus, is directly downwards,
and the K. pocillum obliquely outwards and downwards.
In the interior of the zoecia the arrangements are of the usual
kind, except in the presence of the additional fan- or rather
brush-shaped flexor muscle, which, in this species, is of larger
size or more developed than it is in KH. cyathus (fig. 2.).
The additional muscle connected with the insertion of the
avicularium is absent in K. pocillum. Besides these parts,
there may be also seen within the base of the zoecium
behind, an apparently chitinous process of irregular figure,
and probably hollow. It springs apparently very close to the
spot whence the radical tubes arise, and may have some con-
nection with them. Koren and Danielssen notice a similar
process in A. Smittiz, and I have seen it occasionally of
smaller size than in K. pocillumin K. cyathus. Iam unable
to define its function, but it most certainly does not serve as
the point of attachment for a muscle as supposed by Koren
and Danielssen.
In K. pocillum the avicularium is of larger size, and wider
in proportion to its length than in K. cyathus, resembling
in that respect the avicularium of XH. arborescens, but other-
wise they are alike, both containing, besides the usual
NOTES ON A PECULIAR FORM CF POLYZOA. 9
muscles, a digitiform glandular sac, fine branching nucleated
fibres, which may be nervous.
I have as yet scarcely adverted tothe most remarkable
feature of Kinetoskias, viz. the peduncle or stem, which
appears to exist in all the species, though it is not
shown in Professor Smitt’s figure of his H. wmbella, having
probably, as I should imagine, become accidentally detached.
The mode of formation of this part of the zoarlum, which
is undoubtedly the homologue of the bundle of separate
radical tubes socommonly met with among the Polyzoa, is
extremely curious and interesting, and at the same time, in
some points as yet, more or less obscure ; as, in fact, may be
said respecting the mode of formation and development of
the more ordinary form of radical tubes.
In the more common form they are cylindrical, jointed,
chitinous tubes, with rather thick walls, and with very
scanty contents, beyond a few minute granular particles and
irregular threads, representing, as it would seem, the
remains of an endosarc, with which, in order that their pro-
gressive increase in length, and occasionally complicated
branching, &c., may be effected, we must suppose the tube
to be furnished. In fact, it is otherwise impossible, without
assuming the presence of a germinal material to account
for the fact, that even after the tubes have attained a con-
siderable length the extremity, or a considerable part of the
tube, may undergo great changes in form, as is seen in the
production of hooks and other means of ensuring adhesion
to foreign bodies; changes showing a most extraordinary
adaptability to circumstances. Not the least remarkable of
these adaptations is the division of the extremity of the
tube into a multitude of very minute tubular filaments,
each of which may be traced into independent connection
with some small foreign body. In the deep oceanic forms
these are most usually dead globzgerina shells, or the skele-
tons of other foraminifera, so that having no more stable
foundation than the soft globigerina ooze, which forms so
extensively the bottom of the ocean, the delicate Polyzoan
growths which inhabit those profound depths, are able to
support themselves by the innumerable multitude of solid
particles to which they are attached by the hair-like
terminations of the radical fibres.
And this is well shown in the case of Ainetoskias, in
which the dilated lower end of the peduncle breaks up
into a thick and dense tuft of excessively fine filaments, at
the end of each of which, when the tuft is slightly teased
out, a globigerina, or other foraminiferous shell, is seen to be
10 GEORGE BUSK.
firmly attached. In many instances the filament may be
seen entering the cavity of the empty shell and coiling
about within it.!
It is difficult to imagine how this subdivision of the
distal end of the tube or stem can take place, unless at
that part there is active power of growth, as at the ex-
tremities of the root fibres in plants, though in a different
and at present unknown way. Anda still more remarkable
fact is the power of adaptation to the environment
that is possessed by these delicate filaments, which might
almost lead to the conclusion that an active living power
resides in even the ultimate fibrille.
In Kinetoskias the peduncle, as I have observed, repre-
sents a radical tube, or rather, it may be said, a coalesced
bundle of tubes.
The wall of the peduncle, in the living or fresh condition,
is described by Sir C, W. Thomson as being as clear as
glass, and it retains this transparency scarcely impaired
even after long immersion in alcohol. Unlike the radical
tubes in all other Polyzoa that I have examined, the
corresponding structures in Anetoskias have no action on
polarised light.” Though very thin the wall is extremely
tough, and beyond an obscure appearance, in the contracted
state, of a very delicate, longitudinal, irregular striation, no
trace of structure can be observed in it.
Within, as I have stated, the remains of a very delicate
endosare or cyst may be observed, as represented by a few
scattered, minute nuclear bodies, and irregular branching
filamentous strings. ;
I have already cited Professor Smitt’s account of the mode
of formation of the radical tube or stem and sheathing mem-
brane in J. arborescens, and this, in the main, is equally
applicable to A. cyathus and A. poctllum.
In fig. 5 is represented the bifurcation of one of the
branches in the latter species, just above the point at which
the branches are connected by the sheathing, umbrella-like
“ale
n this figure are shown delicate, dilated, radical tubes,
passing across from one branch to the other. These ttibes
arise from the constricted part of the 2owcium behind and
immediately above its point of origin from the subjacent
one. And they are apparently inserted into the correspond-
ing point of the zoccia in the opposite bratich. The ttibes
1 This arrangement, however, is equally well shown in many other of the
abyssal forms of Bugula, Bicellaria, and other genera.
2 Which would probably indicate the absence of any calcareous element,
NOTES ON A PECULIAR FORM OF POLYZOA. Ye
may be seen to arise with a small transparent protrusion (a,
a, a, a), which gradually increases in length and diameter,
but in the latter sense very irregularly. Whether those
tubes, which are attached at both ends, arise at one end and
are inserted by the other, or whether the continuous tube is
formed by the coalescence of a separate one from each side, I
ain unable to determine, but am inclined, from the appear-
ance the connecting tubes sometimes exhibit, to think that
the latter supposition is the more probable.
The continuous web-like connecting membrane appears
in like manner to be formed by the lateral fusion of similar
connecting tubes. But how the peduncle itself below the
constriction at which it is attached to the sheathing mem-
brane is formed is very difficult of explanation. It seems
to me not improbable that the stem, notwithstanding its size
and length, actually represents merely a segment or inter-
node of a largely dilated radical tube, extending from the
point of constriction above to the lower expanded end, where
it breaks up into the bundle of fibres and fibrille, all of
which, it may be observed, are more or less distinctly divided
into joints or internodes, as is the case almost universally,
so far as I am aware, in all radical tubes among the Polyzoa.
In Kinetoskias cyathus I have not noticed any similar
connecting tubes between contiguous branches, but the mode
of formation of the web-like expansion is very plainly shown
to arise from the coalescence of radical tubes.
In fig. 4 is shown the bifurcation of a branch at a point a
little above and including a portion of the edge of the web,
whilst on the two outer sides of the figure are shown
adherent portions of the same. It will be seen, as described
by Professor Smitt, that a radical tube arising from the
hinder and inferior part of a zocecium descends behind the
outer border of the subjacent ones, and that the descending
tubes on both sides becoming dilated, and gradually ap-
proaching each other, eventually coalesce to form the mem-
branous expansion by which the branches are connected.
It is to be remarked, however, that at the angle formed by
the edge of the web (8), the contents exhibit an aggrega-
tion of minute germinal corpuscles, exactly like those which
characterise the endosare in cell-budding zocecia. From
this one might almost be tempted to suppose that the
radical web possessed an innate power of growth or devel-
opment like an ordinary zoecium, and that it is not alto-
gether beyond the bounds of probability that it may, in
some cases, throw tubular prolongations wpwards along the
sides of the zowcia above. This surmise is strengthened by
12 GEORGE BUSK.
the circumstance that occasionally the lateral tube may be
seen terminating in a rounded extremity, not at the con-
stricted base of the zocecium as usual, but at about the
middle of its length, being, as it were, simply applied, like
ivy to a wall, and without entering the zoecium. In most
cases, however, the radical tubes may be seen entering or
emerging from the usual point at the base of the zowcium.
The inter-connection of the branches of a ramose zoarium
by transverse tubes of the same nature as radical tubes is of
common occurrence in more than one family of Polyzoa.
As instances may be cited, among the Cabereide, the well-
known Canda arachnoides with which I think the Caberea
(or Canda) reticulata of Smitt! should be associated as a
variety, whilst in the genus Bugula the occurrence of such a
condition may be observed in several species. Of these I
would more particularly notice two as yet undescribed forms
in the Challenger collection, which I propose to name
Bugula reticulata (fig. 7) and Bugula unicornis (fig. 8), in
which this mode of connection is very well displayed; but
in both these instances, as well as in Canda arachnoides, the
connecting tube is distinctly seen to arise from a zoecium
in one of the branches, and to be attached to the other
branch by means of clasping fibres, or by an expanded disc,
obviously in this respect resembling a common condition in
the radical tubes. In this respect, therefore, differing from
the apparent condition of the transverse connecting tubes in
Kinetoskias pocillum.
In a third species of Bugula, also,as yet unpublished,
which I propose to name Bugula mirabilis, although
there are no connecting tubes between the branches, the
-mode in which the radical tubes are collected into a long,
rope-like peduncle, shows a complete analogy with, or
approach to, the assumed mode of origin of the peduncle in
Kinetoskias. In fig. 6 is represented the terminal portion
of the zoarium of B. mirabilis, composed, as will be seen, of
a bundle of tubes arising from the usual point in the lower
zocecia, and assembled into a close fasciculus, in which some
of the tubes, in fact, may be seen in such intimate union as
to render it uncertain whether their Jumina are not con-
fluent. The branching terminal portion of one of the radi-
cal tubes is shown subdividing into slender-jointed filaments,
each of which, as in Avmetoskias and many other radicellate
forms, is attached individually to a foreign body; and the
figure also shows the segmented condition of the tube and
filaments.
1 ¢ Floridan Bryozoa,’ p. xvi, pl. v, figs. 43-—46,
NOTES ON A PRCULIAR FORM OF POLYZOA, 13
In this particular species it will also be seen that the
growth of the zoarium commences with an enormously elon-
gated zocecium, from the bottom of which two prolongations
are continued, which at the upper part are slightly calca-
reous, but below become altogether chitinous or horny, and
exactly like the other radical tubes. In fact, the branched
termination shown in the figure belongs to one of these
initial tubes as they may be termed.
That the radical and connecting tubes, like the avicularia
and vibracula, represent modified zooids, is, I believe, gene-
rally admitted; nor can it be denied in this case that
each successive joint or internode is a distinct zooid. In
confirmation of this view I would take this opportunity of
citing a very striking exemplification. This is afforded in a
species of Carbasea (C.ovoidea, Bk.), in which, from the edge
of the fronds, may frequently be seen numerous filamentous
tubular processes, in all respects homologous with radical
tubes, and like those destined to afford attachment to
foreign bodies, or between the separate fronds themselves.
A portion of the edge of a frond of this Carbasea is shown
in fig. 9,in which it will be seen that cells of irregular
form, and never containing a polypide or other structure,
beyond the usual granular endosare and branching fibres,
lie along the border. And that from some of these aborted
cells (for they cannot be termed zocecia) tubular-jointed fila-
ments arise, each of which may, in fact, be considered as repre-
senting one of the longitudinal series of zocecia in the frond.
At @ a short tubular process is seen from which two
tubes arise, exactly in the same way that two zoccia arise
in the course of the longitudinal series of ordinary zocecia ;
and what is very remarkable, as proving the homology of
these aborted zocecia with those of the ordinary kind, at @
the first internode of one of the filaments is actually fur-
nished with a semicircular lip, although there is not the
faintest indication of muscles or polypide in the interior.
The growing end of the tubular filament presents a granular
substance in the interior (0), precisely like that with which
all the young budding zocecia are filled.
These marginal cells and their tubular prolongations
appear to me to afford the clearest possible evidence of the
true nature of the radical tubes and clasping organs of the
Polyzoa.!
Note.—Since the above was written I have noticed in a
1 In Bicelluria and in Notamia it may almost be said that the inhabited
part of the zocecia is simply a dilatation at one part of the internode of
a radical tube, which is continued to the ultimate extremity of the branch.
14 GEORGE BUSK.
species belonging to an abyssal genus, which I propose to
name Angularia, a web-like expansion at the angle of most
of the bifurcations, which is sometimes of considerable
extent, and apparently homologous with that at the base of
Kinetoskias. In this case, however, the web seems to be
formed by an expansion and reduplication of a general
epitheca, which is strongly developed in this and other of
the abyssal forms.
GERMINATION AND HISTOLOGY OF WELWiTSCHIA MIRABILIS, 15
On the Germination and Histotocy of the Srnpiine of
WELWITSCHIA MIRABILIS, By F. Orven Bower,
B.A., Camb. With Plates III and IV.
The Mature Embryo.
Tue development of the embryo of Welwitschia has been
described by Sir J. D. Hooker, in his monograph on the
plant (‘ Trans. Linn. Soc.,’ vol. xxiv), and again by Stras-
burger (‘ Angiosp. und Gymnosp.,’ p. 155). I find the struc-
ture of the mature embryo to correspond in the main with
these descriptions, but the embryos, which I have had the
opportunity of examining, are larger, and possibly better
matured than those described by the latter writer; while a
comparison of his fig. 92 with fig. 1° a, 8, c, will show a
difference of form, as well as of structure.
I find the mature embryo to consist of a straight radicle,
with largely developed root cap. ‘To the apex of the radicle
adheres the suspensor, which, together with the embryonic
tubes (embryonal-schlaiiche), forms a mass of considerable
size. Surrounding the body of the embryo may be seen a
swelling or collar (fig. 1 x). Passing from this towards the
apex of the embryo, there is a sudden diminution in thick-
ness, and at a short distance above the collar are borne the
two cotyledons. From a comparison of fig. 1 A and B, it
will be seen that the hypo-cotyledonary part of the embryo is
nearly cylindrical, the cotyledons only being compressed.
The plane of their compression is that in which the whole
seed is flattened. A longitudinal section (fig. 1 c) shows
that between the cotyledons lies the apical cone of the
plumule. This, as stated by Strasburger, remains undeve-
loped, as a simple papilla of tissue, up to the time of
maturity of the embryo. From 2 longitudinal section it is
seen that the radicle is short in comparison with the root
cap, and that the latter extends back almost to the thickest
part of the collar. The epidermis proper, which covers the
cotyledons and the hypo-cotyledonary stem, loses its identity
at the point where the root cap begins. From here onwards
to the apex of the radicle, the external covering is made up
of a succession of layers of the rootcap. These merge imper-
ceptibly into the cortical tissue. At the apex of the radicle
the arrangement of tissues corresponds to the general type
for the conifere. In Welwitschia, however, the tissues of
the root cap are more diagrammatically arranged than is
usual in the group, the regularity of the central series of
16 F, ORPEN BOWER.
cells being maintained up to the mass of suspensors and
embryonic tubes, which cover the apex of the root cap.
Germination.
On being exposed to conditions favorable for germination
the seed swells, and the embryo begins to increase in length.
The root is the first to push its way out through the ruptured
testa. The elongation which produces this result takes
place chiefly in the tissues of the root itself, the hypo-
cotyledonary stem increasing at first only slightly in length.!
The point of perforation of the testa is near to the apex of
the seed, but is variable according to the position of the seed
during germination. It is on the side which happens to be
undermost (figs. 4, 5). The root in its growth pushes aside
the persistent remains of the nucleus, together with the
suspensors, and the apical part of the largely developed root
cap. These may be seen in the germinated seedling attached
laterally to the exterior of the root? (figs. 3, 4).
Thus far the hypo-cotyledonary portion of the stem has
extended only slightly. The cotyledons, however, and the
upper part of the hypo-cotyledonary stem, begin now to in-
crease in length, and the thickest part of the embryo is pushed
out of the cavity of the endosperm. The room thus made is,
however, filled by the growth of a peculiar excrescence from
that side of the hypo-cotyledonary stem, whichis madeconcave
by the curvature of the root downwards.? The first stages of
development of this organ I have unhappily been unable to
follow from want of suitable materials. Long before the
escape of the cotyledons from the seed it may be found
lying side by side with them in the cavity of the endosperm
(fig. 2 4). In form itis wedge-shaped, but with the edge of
the wedge (7. e. the apex of the organ) rounded. It is com-
pressed in a plane parallel to that of the cotyledons.
On searching for this lateral structure in the mature
embryo before germination, no external trace of it was
found, the swollen collar being, as described, uniform round
the axis. Even on cutting sections of the hypo-cotyledonary
1 According to Strasburger (‘ Conif.,’ p. 319), the hypo-cotyledonary stem
usually elongates rapidly during the first stages of germination of the
Conifer.
* Cf., “ Description of Germination in Ephedra,” Strasburger, ‘Conif.,’
. 321. ;
! 3 It is natural for seeds shaped like those of Welwitschia to lie on their
side during germination. The possible case of a seed sown so that the
radicle of the embryo should point vertically downwards, I have never had
the opportunity of observing.
GERMINATION AND HISTOLOGY OF WELWITSCHIA MIRABILIS. 17
stem of the mature embryo, there was not found in the
arrangement of the tissues any indication of this organ, or
apparent preparation for its development; the arrangement
of epidermis and cortical tissue being uniform all round the
stem.
Since my work depended upon a limited number of seeds
only, I was not able to study the early stages of development
of this organ as fully as I should have wished ; nor could I
obtain anything further than the following facts :
In a seed which had been sown three days no change
was found in the embryo. In a seedling of twelve days,
however, the organ was found almost fully formed (fig. 2).
In this case the root had extended to a length of about one
and three quarter inches. The cotyledons, though still
enclosed in the seed, had grown to about one quarter inch
in length. Side by side with these lay the lateral organ,
which had already attained a length almost equal to that of
the cotyledons. From these observations we see that the
development of the organ is, like others of the first processes
of germination, very rapid.
In all cases of seeds sown flat, the position of the lateral
organs with relation to the cotyledons, was found to be as
represented in fig. 2. In seeds sown on edge, as soon as
room is allowed by the extrusion of the root and thicker
part of the hypo-cotyledonary stem, the cotyledons suffer
torsion in the cavity of the endosperm; so that the body of
the embryo is rotated on its axis, and thus it assumes a
position, relatively to the direction of gravity, similar to that
in the case of the seed sown flat. The lateral organ is
meanwhile developed in the same position, relatively to
the rest of the embryo, as in the former case (fig. 3).
It always appears on that side of the stem which is made
concave by the curving of the root downwards. Hence
it appears that the direction of gravity, relatively to the
germinating seed, has an indirect determining influence
upon its position. If we consider the mature embryo,
we shall see that the lateral organ might be formed at
either of two points (¢.e. either of the points marked z
in the fig. 1 8B). It depends upon the position of the seed,
and hence upon the direction of gravity relatively to it, at
which of these two points the development shall take place.
As to what happens when the plane of the seed or the axis
of the embryo is exactly vertical I have no observations
to offer. These cases would be particularly interesting for
comparison with Ephedra.
1 Strasburger, ‘ Conif.,’ p. 320.
VOL. XXI.—NEW SER. B
18 P. ORPEN BOWER.
During the development of this lateral organ, the cotyle-
dons gradually increase in length, while the hypo-cotyle-
donary stem also extends. The result of this is the gradual
arching of the upper part of the seedling (fig. 3) till it bursts
through the testa. The lower limb of the arch extends
more rapidly than the upper. The cotyledons are thus with-
drawn from the endosperm. The point of perforation of
the testa by the stem is variable; it is usually on the oppo-
site side of the seed from the hole made by the root, and is
often quite separate from this (fig.4). In other cases the two
perforations run together as a wide split of the testa (fig. 95).
When freed the hypo-cotyledonary stem straightens itself,
and now by its further extension the cotyledons are raised
above the surface of the soil, and expand as green assimilat-
ing leaves. The lateral organ, however, remains in close
connection with the endosperm, and, growing further, com-
pletely fills the cavity vacated by the embryo.
That the lateral organ we have been describing is a
means of transfer of nutrient materials from the endosperm
to the seedling is proved by the following facts:—(1) That
the endosperm still contains a considerable quantity of
nutritious substances after the cotyledons free themselves
from it. (2) That the cell walls of the outer cells of the
organ are not cuticularised. (3) That it is not a perma-
nently useful organ,since, when the endosperm is exhausted it
also shrivels. ‘To express this view of its function, and at
the same time avoid any term bearing with it a definite
morphological idea, it may be called the “ Feeder.”
We have seen that the plumule in the mature embryo
consists of a simple papilla of tissue. When the cotyledons
have expanded it appears, however, to have developed fur-
ther. The time of this change I have not been able to
ascertain accurately. In seedlings, such as those repre-
sented in figs. 4, 5, the plumule consists of a pair of lateral
leaves, decussating with the cotyledons; between these may
be seen the apical cone (fig. 9). I have not, in any of the
seedlings grown at Kew, cbserved any further development
of the plumule than that described. The size and form of
the plumular leaves of the oldest seedlings now growing at
Kew may be gathered from figs. 7 and 8, which represent
plants of ten and a half weeks’ growth. The cotyledons
are,as stated, two in number. In one case (fig. 5) I observed
three, but this may be explained by a splitting of one of the
typical pair. Moreover, the position of the two smaller
cotyledons in this case, with regard to the plumule, and the
other cotyledon, makes this almost certain.
GERMINATION AND HISTOLOGY OF WELWITSCHIA MIRABILIS, 19
The form and size of the cotyledons may be gathered from
the figures 7 and 8. While still enclosed in the seed they
are yellowish orange; they maintain this colour some time
after appearing above the soil. Finally, they become green,
and in this condition they remain persistent for a consider-
able time; they are at all times glabrous and have entire
margins. Each cotyledon has two main central bundles,
which run parallel to one another, and two lateral ones
parallel to these. Each of the four gives off smaller lateral
branches, which anastomose freely. 1 have observed no
axillary buds in the axils of the cotyledons as in Ephedra.
The hypo-cotyledonary stem is variable in length, from
13 to 23 inches. It is compressed in the plane of the cotyle-
dons, and is slightly swollen just below the point of junction
with them. The root, which is a direct elongation of the
radicle, has, in the plants already grown, attained a length
of 4 ot 5 inches, without a single lateral branch, with the
exception of one case where the apex of the root had been
injured ; here a lateral root had been formed.
‘I'he undoubted presence of a pair of plumular leaves in
Welwitschia suggested a comparison of the young seedlings
with the smallest specimens, preserved in the Kew museums.
The result is the discovery of evident traces of the existence
of leaves, previous to the large expanded pair, which are
characteristic of the plant. Fig. 10 represents the apex of
the youngest plant in the Kew collections, as seen from
above. Here may be seen, protruding from the stem below
the main pair of leaves, the ragged remains of fibro-vascular
bundles, which run directly into the tissues of the stem.
These, from their position and apparent course, point to the
existence of a previous pair of leaves, which have decussated
with the present pair, but which have rotted off. Traces of
these may be found in even older specimens than the one
figured, so that, not from one plant only, but from several
may be deduced the conclusion, that the main leaves of
Welwitschia are not persistent cotyledons, but leaves de-
rived from the plumule. Hitherto we have only seen two
plumular leaves formed; we may, therefore, reasonably
conjecture that those plumular leaves are persistent as the
typical pair of leaves of Welwitschia. ‘The absolute proof
of this will, we may hope, be afforded by the successful
growth of the seedlings now living at Kew.!
1 Concerning the morphological value of the structures seen between
the leaves of the plant, represented in fig. 10, I am not at present in a
position to make any statement.
20 P. ORPEN BOWER.
EMistology of the Seedling.
If transverse sections be cut of the hypo-cotyledonary
stem of the seedling, the tissues will be found to be ar-
ranged in the following manner :—At the periphery of the
section is an epidermal layer with cuticularised outer walls.
Here and there are stomata, which demand no special notice
beyond their guard cells being slightly depressed. Beneath
the epidermis is a fairly regular cortical tissue, in which,
after treatment with alcohol, are found large quantities of
the sphere crystals of inulin. The outer layers of cells of
the cortical tissue have, in some cases, cuticularised walls
(figs. 11, 12). Scattered irregularly through the cortical
tissue, but more especially towards the outside are scleren-
chymatous cells. These occur singly, or in groups of two
to five or six. This sclerenchyma is not very constant in
quantity, and was in some cases found to be absent. To-
wards the centre of the section will be found four fibro-
vascular bundles, arranged as in fig 11. They are peculiar
in having the xylem portion turned towards the periphery,
and the phloem towards the centre of the stem. Moreover,
the xylem tails off laterally in a manner represented in fig.
11 by the lines marked pr, zy.
The structure of the individual bundle corresponds pretty
closely with that of the leaf as described by De Bary,'
although not so complicated.
On reference to fig. 13, which represents the fibro-vascular
bundle of the young hypo-cotyledonary stem before exten-
sion takes place, it will be seen that the first developed
xylem elements are drawn out into a long lateral series.
Development begins at the end of this series, marked pr, zy.
and progresses in the direction shown: by the arrow. The
further development of xylem occurs only opposite the later-
formed elements, marked ay, fig. 13. A layer of cells
(cb) have already begun to divide as a cambium layer; and
the cells between this and the already formed xylem are
beginning to thicken their walls, and develop into xylem
elements. The group of cells, with very small cell cavity,
on the central side of the cambium layer, are the protophloem
(pph, fig. 13).
We shall now be in a position better to understand the
mature bundle. Fig. 14 represents a section through a
fibro-vascular bundle taken from a hypo-cotyledonary stem
which is fully extended. Here the protoxylem elements
will be seen to have been drawn out thin by the extension
1 ¢Vergleichende Anatomie,’ p. 347.
GERMINATION AND HISTOLOGY OF WELWITSCHIA MIRABILIS. 2]
of the stem ; and their cell cavity has been almost com-
pletely obliterated, so that they only remain as occasional
irregular masses of lignified wall between the parenchy-
matous cells. In longitudinal section the thickening is
seen to be drawn out into a loose spiral, or sometimes
almost into straight lines. The bearing of this arrange-
ment of the protoxylem will be seen when the course of the
fibro-vascular bundles at the apex of the stem has been
traced.
The constituents of the xylem of the hypo-cotyledonary
stem are the same as described for the leaf bundle.! It will
be noticed that, as we pass from the xylem, through the
cambium, to the phloem, the tissues are arranged in regular
rows, pointing to a development from a cambium layer
which, as was seen (fig. 13), makes its appearance very
early. inch
(1:3 mm.).
This thick lenticular form of Hauerina appears to be
limited in its distribution to the North Atlantic, and
under the name of H. compressa it has been recorded
1«QOn the Miliolitide (Agathistegues, d’Orbigny) of the East Indian
Seas,” part 1, “ Miliola,” ‘Trans. Micros. Soc.,’ London, 1858, vol. vi, N.S.,
p. 53, pl. 5, fig. 10.
NOTES ON RETICULARIAN RHIZOPODA. 47
from the west coast of Scotland.! At times it is not easily
distinguished from Beloculina contraria, for the internal
structure is obscured by the thickness and opacity
of the test; generally, however, there are slight con-
strictions or depressions at the periphery, marking the
sutures.
H. circinata, nov.—Test nautiloid, thin, complanate; com-
posed of two or three convolutions, the last, consisting
of six or seven segments, completely enclosing the
earlier ones. Segments arched, rounded at their peri-
pheral margins; sutural lines marked by external con-
strictions. Colour milky white, sufficiently translucent
to show the outline of the inner whorl of chambers.
Aperture consisting of a number of perforations distri-
buted irregularly over the front of the terminal seg-
ment. Diameter ~/; inch (1° mm.).
vo
Orsito.ites, Lamarck.
Orbitolites laciniatus, nov.—A variety of Orbitolites of the
complex type, figured by Carpenter (‘ Phil. Trans.,’
1856, pl. 5, figs. 2, 3), and by Butschli (in Bronn’s
‘ Klassen und Odrnungen des Thier- Reichs,’ 1880, vol. i,
pl. 5, fig. 4), but in both cases without name. It is little
more than a local variety of Orditolites complanatus,
abundant on the coral reefs of the Friendly Islands and
Fiji; but as it represents the best development of the
structural modifications induced by redundant growth,
it is convenient that it should be distinguished by
name.
The centre of the disc is constructed on the normal
plan, but near the margin it becomes strongly sinuate
or plicate, at the same time splitting so as to forma
double periphery, the two edges of which approximate
at intervals, but otherwise are separated by deep
irregular furrows. Specimens from the localities above-
named are not unfrequently an inch (25° mm.) or more
in diameter.
As?RoruizA, Sandahl.
Astrorhiza crassatina, nov.—Test (typically) elongate, sub-
cylindrical, seldom of uniform breadth, often constricted
near the middle, ends rounded ; consisting of a tube of
greater or less length open at both ends. Walls very
1 “ Rhizopodal Fauna of the Hebrides,” ‘ Report Brit. Ass.,’ 1866 (Trans.
Sections), p. 69.
48
HENRY B, BRADY,
thick, composed of fine sand with but little cement.
Cavity tubular, never of uniform diameter, but swollen
at one or more points so as to form spurious chambers.
Length about ;4; inch (10° mm.).
This form is nearly allied to Astrorhiza granulosa
(Marsipella granulosa, ‘Quart. J. Micr. Sci.,’ vol.
xix, n.s., p. 36, pl. 3, figs. 8, 9), and is perhaps its North
Atlantic representative ; but A. granulosa is of smaller
dimensions, and the chamber-cavity consists of a
narrow tube of even diameter throughout.
A. angulosa, nov.—Test triangular (rarely quadrangular),
depressed, biconvex, with rounded margin ; consists of
a central chamber with radiating tubes, one passing to
each corner, the open ends of which serve as apertures.
Walls relatively very thick, and composed of loosely
cemented fine sand. Diameter, 1 inch (3°6 mm.).
A. angulosa appears to be a short, three-mouthed
variety of A. granulosa, with which species it is found
associated. . In both of these, as also in A. crassatina,
the orifices are often partially blocked with sand-grains,
and not unfrequently are stained reddish brown.
RHABDAMMINA, Sars.
Rhabdammina discreta, nov.—Test cylindrical, open at both
ends ; consisting of a straight or nearly straight tube of
indefinite length, spuriously segmented by slight con-
strictions at irregular intervals. Walls thin, composed
of angular sand-grains firmly cemented; interior smooth.
Specimens nearly an inch (25° mm.) in length are not
uncommon.
BorE.iina, Carpenter.
Botellina labyrinthica, nov.—Test arenaceous, cylindrical
(probably growing attached by one end), straight, or
slightly curved, somewhat irregular in external con-
tour; one end round and more or less inflated, the
other never hitherto found entire. The wall is of firm
consistence and compactly built, except at the rounded
extremity where it becomes a thin incomplete layer of
sand grains with many interstitial openings. The
interior, except near the rounded end, is subdivided
irregularly by a labyrinth of coarse, sandy, spurious
septa. The rounded terminal cavity forms an undi-
vided chamber. Pieces hitherto obtained have seldom
measured more than an inch (20° to 20° mm.), but it
iy Sil
NOTES ON RETICULARIAN RHIZOPODA, 49
is impossible to say what length complete specimens
may attain. The diameter is about +, inch (2°5 mm.).
ReEopuHAx, de Montfort.
Of the monothalamous and moniliform (Lagena-like and
Nodosaria-like) Lituole there are half a dozen unrecorded
modifications of sufficient interest to deserve preliminary
notice.
fteophax ampullacea, nov., is monothalamous and com-
pressed. It bears very much the same relation to R.
difflugiformis that Lagena marginata bears to L. glo-
bosa. Length, ;5 inch (0°85 mm.).
fh. bacillaris, nov., is a long, regularly tapering, slightly
arcuate variety, with very numerous, short segments.
The earlier segments are cylindrical, and have flush
sutures not distinguishable on the exterior, the later ones
sub-spherical. Colour very dark. Length sometimes
nearly + inch (4°7 mm.).
fi. rudis, nov.—The largest species of the subgenus hitherto
met with. Shape long, cylindrical, slightly tapering ;
sides even and unconstricted; extremities rounded.
The walls thicker than those of its congeners and of
looser texture ; composed of fine grey sand. A longi-
tudinal section reveals about six segments, each taper-
ing at the summit to a stoloniferous tube, the mouth of
which, as well as the external orifice, is tinted reddish
brown. Length, 4; inch (10° mm.) or more.
The Rev. A. M. Norman has placed in my hands some
specimens of a form which, though certainly distinct, is
very difficult to separate from this by any positive characters,
The specimens are of smaller size and relatively long and
slender, darker in colour, and more compactly built; but
neither they nor those of the larger species show any
sutural constriction or other external mark of segmentation.
R. dentaliniformis, nov.—A small, delicate variety of R.
scorpiurus, but more slender and regular in contour;
segments five or six in number, elongate, and but
slightly ventricose. Length, +, inch (1'85 mm.).
f. guttifera, nov., has pyriform segments, broadest near
the base, and tapering to a narrow stoloniferous tube
- at the point of union with the succeeding chamber. In
small specimens the base of the segments is often
truncate or even somewhat concave. Number of seg-
ments very variable. Length, seldom exceeding ~; inch
(1'5 mm.).
VOL, XXI,-——-NEW SER. D
50 HENRY B. BRADY.
R. distans, nov.—A thin-shelled, dark-coloured form, never
found entire. Segments distinct, fusiform, tapering
nearly equally at the two ends into stoloniferous tubes,
which are long and slender in proportion to the bulk
of the chambers they unite. Specimens with three
chambers, which are the largest hitherto found, have a
length of nearly 4 inch (4°8 mm.).
HAPLoPHRAGMIUM, Reuss.
Of the section embracing the nautiloid, crozier-shaped
and rotaliform Ztwole, there are amongst the ‘ Chal-
lenger ” collection five species distinct from any hitherto
described, in addition to several that may be left for the
present as more or less doubtful.
Haplophragmium foliaceum, nov., has a very beautiful and
delicate, crozier-shaped test, flat on both sides, and so
thin as to be almost transparent. ‘The segments are
numerous, short and broad, and the peripheral margin
is slightly constricted at the sutures. Length, J, inch
(1:3 mm.).
Hi. rotulatum, nov.—A sandy isomorph of Anomalina coro-
nata, nautiloid in contour and biconcave; the um-
bilicus is deeply sunk on both faces, and the periphery
broad and square, often somewhat oblique. Diameter,
¢@ inch (0°6 mm.) or less.
H. scitulum, nov.—Test nautiloid, excavated at the umbi-
licus, rounded at the periphery; composed of two to
three convolutions, the outermost consisting of from
eight to eleven segments only partially enclosing the
earlier ones. Segments compactly fitted, with little
or no depression at the sutural lines. Shell-wall finely
arenaceous, nearly smooth externally, and of clear
yellow-brown colour. Diameter, =; inch (0°8 mm.).
H. turbinatum, nov.—Test rotaliform, subglobular, depressed
at the umbilicus; consisting of less than two convolu-
tions. Segments somewhat ventricose ; numbering about
six in the peripheral whorl. Diameter, ;4, inch (0°75
mm.).
This form resembles H. subglobosum in size and tex-
ture, but differs from it in being rotaliform and unsym-
metrical, not nautiloid.
Hi. nanum, TSM: miuute, rotaliform, depressed ; superior
face somewhat convex; inferior, plane, more or less
excavated at the umbilicus; margin rounded, lobulate.
Consists of about two revolutions, each composed of
NOTES ON RETICULARIAN RAILZOPODA. oF
about six inflated segments, often irregular in shape
and disposition. Shell texture thin, resembling that
of H. canariense. Diameter, =; inch (0°34 mm.).
PxacopsiLina, d’Orbigny.
There is, in addition, one simple adherent Lituoline
species resembling in form the Sguamulina of Max Schultze,
but arenaceous instead of porcellanous in texture.
Placopsilina bulla, nov.—Test adherent; highly convex or
approximately hemispherical but slightly longer in one
diameter than the other; with a simple, rounded,
pouting aperture at each ‘end, close to the base. Walls
thick, somewhat loosely sandy. Diameter, ~; inch
(0°75 mm.).
Ammopiscus, Reuss.
Of the free non-septate Trochammine only two forms
require present notice; both are somewhat remarkable for
their size.
Ammodiscus tenuis, nov.,is a large, thin, planospiral variety,
consisting of a few broad, somewhat overlapping, con-
volutions. It bears the same relation to A. encerta that
Cornuspira foliacea bears to C. involvens. Diameter,
sometimes + inch (3° mm.).
A. spectabilis, nov.—By far the largest species of the non-
septate group, is composed of a tube wound upon itself,
not regularly and symmetrically so as to retain a rec-
tilimear shape (like A. Shoneanus), but in curved or
twisted fashion, so as to form an arcuate or subhelicoid
test. The shell-wall is very thin, the exterior some-
what rougher than usual amongst the Trochammine,
the interior smooth and polished. Diameter, + to +
inch (5° to 6° mm.).
Hormosina, Brady.
The following are representatives of the uniserial or
moniliform section of the genus:
Hormosina Carpenter, nov.—A fine species figured by Dr.
Carpenter in his treatise on the‘ Microscope’ (5th ed.,
1875, p. 531, fig. f), under the general name “ Monili-
form Lituola,” pretty common in deep water in the
North Atlantic and elsewhere. It consists of numerous,
elongate, pyriform segments, increasing but slightly in
size as they succeed each other ; connected end to end in
a curved or crooked, never (as a rule) ina straight line.
52
HENRY B. BRADY,
The shell-wall is finely arenaceous, compactly cemented,
and nearly smooth on both its inner and outer surface,
except when irregularity of the exterior is produced by
sponge spicules only partially incorporated. Length,
4+ inch (13° mm.) or even more.
H. monile, nov.—A variety with similar general characters
to that last described, but differing in its comparatively
small dimensions and in the form of its segments. The
segments are short, subspherical, and uniform in size.
The length of the longest specimen hitherto obtained
is about + inch (6° mm.).
H. Normani, nov., has an irregularly constructed test com-
posed of few spherical segments, of which the earlier
ones are relatively small, the final one usually very
large. The orifice is seldom at the apex of the cham-
bers, but often at some point of the periphery, very near
to the entrance of the last stoloniferous tube, so that
the new segment is sometimes put on obliquely, some-
times at right angles to the previous one, or even, as is
not unfrequently the case, directed backwards, as a
result of which, the test assumes a great variety of irre-
gular forms. Length, 4 inch (8:5 mm).
TRocHAMMINA, Parker & Jones,
Of the nautiloid and rotaliform Trochammine only two
minute species require notice, in addition to those described
in a former paper.
Trochammina galeata, nov.—Test nautiloid and symmetrical,
Tr.
subglobular or compressed, showing only three seg-
ments externally, of which the final one constitutes
much more than half the visible shell. Aperture situated
on the peripheral face of the final segment, near its junc-
tion with the antepenultimate; simple, often imme-
diately below a projection of the shell-wall. Diameter,
=, inch (0°5 mm.).
This species resembles Tr. ringens, described in a
former paper (‘ Quart. Journ. Micr. Sci.,’ vol. xix, N.S.,’
p- 57, Pl. 5, fig. 12 a, 6), in many particulars, but it.
is scarcely so large, and is relatively thicker; its few
segments, and the disproportionate size and embracing
contour of the final chamber, are sufficiently distinc-
tive.
nitida, nov. — Test regular, rotaliform, compressed ,
superior face nearly flat; inferior convex, somewhat
excavated at the umbilicus; margin rounded, slightly
NOTES ON RETICULARIAN RHIZOPODA. 53
depressed at the sutures. Consists of two to three con-
volutions, of which the final one has about nine seg-
ments. Diameter, ;!> inch (0°5 mm.).
Cyciammina, Brady.
The genus Cyclammina is of considerable importance,
inasmuch as it presents the best development amongst living
Foraminifera, of finely tubular cancellated growths of shell
substance filling the chamber cavities—a sort of structure
differing widely from the mere subdivision of the chambers
by the building in of large sand-grains, which is not un-
common amongst arenaceous types. ‘There are two interest-
ing modifications of C. cancellata amongst the ‘‘ Challenger”
gatherings, which, though perhaps only local varieties, differ
sufficiently from the typical form to deserve distinctive
names.
Cyclammina orbicularis,nov.—A subglobular variety, bearing
about the same morphological relation to the type
that Nonionina pompilioides does to N. depressula, only
that it is of much smaller size.
C. pusilla, nov., has a minute, biconvex test, depressed at
the umbilici, and with thin, sharp, slightly lobulate
periphery. A horizontal section shows that it consists
of about three complete convolutions, the last of which
has about fifteen segments. The cancellated structure
is but little developed, there being only sufficient to
form a superficial reticulation over the inner surface of
the chamber walls. Diameter, =4 inch (1: mm.).
TEXTULARIA, Defrance.
Textularia siphonifera, nov.—Test subcylindrical, nearly
-roundin transverse section, tapering and pointed at the
. primordial end ; each of the two opposing series of cham-
bers furnished with from two to four rows of tubulated
fistulose openings, arranged with more or less regularity.
Length, ;/; inch (1'5 mm.).
BicENERINA, d’Orbigny.
Bigenerina robusta, nov.—Test elongate, compressed in its
earlier (biserial) portion, cylindrical in its later (uni-
serial) growth. Uniserial segments numerous, short,
somewhat irregular, often ventricose at their periphery.
Aperture simple and Textularian in the biserial seg-
ments, becoming multiple and porous in the uniserial
portion ; the pores either arranged in a ring or irregu-
54 HENRY B. BRADY.
larly distributed in the central part of the exposed face
of the terminal chamber. Interior non-labyrinthic.
Length, about + inch (4:8 mm.).
This species is of much interest in its bearing upon a
group of Carboniferous Foraminifera which have been a source
of difficulty to paleontologists. The fossils alluded to were
described by myself some years ago under the provisional
generic name Climacammina,' and since that time similar
specimens from the Russian Carboniferous beds have been
figured by Prof. von Moller with the fresh generic term Crv-
brostomum.? The characters of most, if not of all the fossil
specimens, have been a good deal obscured by external
agencies, such as pressure and the process of mineralisation,
but they are easily recognised in the presence of the recent
examples which we now have for comparison ; indeed, it is
not altogether easy to find positive features whereby to
distinguish the palzeozoic from the living species. Through-
out the whole genus Teztularia the aperture is one of the
most variable features, and as the only conspicuous point in
which the dimorphous forms under consideration differ from
the typical Bigenerina is in the fact that their later segments
have a porous instead of the usual simple aperture, I can
see nothing to be gained by employing a distinctive generic
or subgeneric name for them.
CurysaLipina, d’Orbigny.
Chrysalidina dimorpha, nov.—Test elongate, triangular,
tapering; the three sides nearly equal, the angles sub-
carinate ; inferior extremity pointed, superior broad and
convex. ‘Test composed of many segments, the earlier
ones triserial, the later uniserial. Aperture consisting
of numerous minute perforations on the superior face
of the terminal segment. Texture hyaline. Length,
+5 inch (0°5 mm.).
CLavuLina, d’Orbigny.
Clavulina caperata, nov.—Test elongate, subcylindrical or
fusiform, broadest below the middle; trarsverse section
nearly circular throughout; triserial portion relatively
very large. Inferior extremity tapering to a point,
superior narrow, rounded, or truncate. Segments very
numerous, irregular in form and arrangement, the
1 Monograph of Carboniferous and Permian Foraminifera ’ (1876),
oi.
Ps ‘Mém. Acad. Sci., St. Petersburg,’ ser. 7, vol. xxvii (1879), p. 39.
er
NOTES ON RETICULARIAN RHIZOPODA, 55
sutures marked by external limbate lines; chamber
cavities much subdivided. Aperture central, terminal,
with raised valvular lip. Length, 5 inch (2°5 mm.).
C. indiscreta, nov.—Test elongate, three-sided, broad near
the middle, and tapering towards both ends; edges
rounded, except near the inferior end, where they are
acute, and terminate in a point. Segments few, septi-
tion obscure externally. ‘Texture subarenaceous, com-
pact; surface smooth. Aperture a neat, round terminal
orifice. Length, ~; inch (1°6 mm.).
Triraxta, Reuss.
Tritaxia lepida, nov.—Test triquetrous, broadest near the
middle, tapering towards the ends; the three sides
nearly equal, the angles sharp or subcarinate. Superior
end rounded and terminating in a short neck; inferior,
tapering to a sharp point. Texture hyaline. Length
=5 inch (0°3 mm.).
Buuimrina, d Orbigny.
Bulimina subteres, nov.—This name has been given to a
small Bulimine form frequent in northern seas, but which
hitherto has had no well-defined position. In my paper
on North Polar Rhizopoda (‘Ann. and Mag. Nat. Hist.,’
ser. 5, vol. i, p. 436, pl. 21, fig. 12) it was provisionally
assigned to B. elegantissima, d’Orb., with the remark
that the specimens were “ not of the precise contour by
which the species was usually recognised ;” and that
though “the segments were similarly arranged, they
were relatively shorter, and there were fewer in each
convolution.” It might have been added that the aper-
ture is usually inserted further from the apex of the
shell. In point of fact the species is almost equall
related to B. elegantissima, d’Orb., and B. (Robertina)
arctica, @ Orb., but it has larger, broader segments than
either, and is altogether less elegantly made. Speci-
mens from the North Atlantic are commonly from =,
to =; inch (0-4 mm. to 0°6 mm.) in length, broad and
rounded at the superior end, and tapering to a point;
the sides are convex and but slightly excavated at the
sutural lines.
Messrs. Parker and Jones (‘ Phil. Trans.,’ vol. elv,
p- 375) show that the two d’Orbignian forms above
mentioned are in near relationship, but I cannot
follow them so far as to include both under the same
name; indeed, I should prefer to assign some of the
56 HENRY B. BRADY,
specimens they figure (op. cit. pl. 15, figs. 13—17) to the
species now described rather than to B. elegantissima.
B. subcylindrica, nov.,.is another form belonging to the
same group as B subteres. The test is elongate, sub-
cylindrical (not tapering), the two ends equally rounded,
and the surface but little excavated at the sutures.
The segments are few, and their spiral arrangement is
very obscure: the aperture takes the form of a narrow,
nearly erect slit, near the base of the final segment.
Length, => inch (0°5 mm.).
B. Williamsoniana, nov.—Test elongate, cylindrical, more
or less sinuate in contour, circular in transverse sec-
tion ; composed of a spiral band of long narrow, nearly
erect segments. Inferior extremity slightly tapering and
rounded, superior obliquely truncate. Surface traversed
from end to end by a series of somewhat sinuate and
diagonal parallel coste, which entirely obscure the
internal structure. Aperture simple, situate in a depres-
sion at the centre of the oblique superior face, bordered
by radiating lines. Length, ,!; inch (0°64 mm.) or less.
Borivina, d’Orbigny.
Excepting the genus Lagena, there is no group of hyaline
Foraminifera the knowledge of the varietal modifications of
which has received larger accessions from the study of the
“ Challenger ” material, than that comprising the aberrant
forms of Bulimina, included under the subgeneric terms
Virgulina and Bolivina. Both diverge from the typical plan
of structure in their tendency to become more or less regu-
larly biserial, instead of spiral, in the arrangement of their
chambers, whilst they usually retain the characteristic
Bulimine aperture. It is impossible to separate these two
subgenera one from another by any well-defined or perma-
nent peculiarity; all that can be said to distinguish them
is that Virgulina is more Bulimine and less Textula-
rian in the disposition of its segments, and that Bolivia is
more Textularian and less Bulimine. Whilst, therefore, it
is comparatively easy to associate Vergulina with its type,
Bolivina often only betrays its affinity by the aperture, which
is either comma-shaped, twisted, toothed, unsymmetrically
oval, or of some other form within the range of variation to
be found in Bulimina itself. In the varieties of Vérgu-
lina we find all the links connecting Bolivia with the
typical Bulimina. Two or three undescribed species of
Virgulina way be omitted from the present notice, as de-
scriptions in few words would be scarcely intelligible with-
NOTES ON RETICULARIAN RHIZOPODA. 57
out figures; of Bolivina the following new forms may be
placed on record.
Bolivina porrecta, nov.—Test elongate, straight, slightly
tapering, finger-shaped, somewhat compressed ; margin
and ends rounded. Segments about as broad as long,
the earlier ones arranged on the normal Textularian
plan, the later ones taking a nearly triangular form,
each extending the entire width of the test, the sutures
forming a zigzag line from side to side. Walls thin
and clear, very finely perforated; sutural depressions
bia slight. Aperture large, terminal, oblique. Length,
i= Inch “(0-9 mm.).
B. limbata, nov.—Test elongate, tapering, compressed, more
or less twisted; margin angular or only slightly
rounded, sinuate. Sutures irregularly curved, limbate,
especially near the points of contact of the two series of
segments on both faces of the shell. Length, ;> inch,
(0°75 mm.).
B. tenuis, nov.—Test thin, outspread, broadly elliptical,
slightly convex on both sides ; margin acute. Segments
few, each with a sort of supplementary lobe, the lobes
collectively presenting the appearance of a series of
chamberlets down the median line. Aperture on the
oblique face of the terminal chamber surrounded by
radiating lines. Dimensions, ~, by ;4, inch (0°3 by
0:26 mm.).
B. laevigata, nov.—Test elongate, thin, complanate, broadest
at the centre, tapering and rounded towards the ends.
Segments few in number, Textularian in arrangement,
broad, flattened on both faces, bordered both at sutures
and periphery by a narrow band of clear shell-substance.
Sutures flush; aperture large, irregularly oval, oblique.
Length, 4, inch (0°43 mm.).
B. tortuosa, nov.—Test elongate, tapering, broadest near the
top; the sides bent obliquely towards the median line,
so as to give the whole shell a twisted contour ; margin
thin, sharp, lobulate. Segments numerous, long, narrow,
projecting and rounded at the free ends. Sheil conspi-
cuously perforated. Length, 3, inch (0°45 mm.).
B. pygmea, nov.—Test short, broad, biconvex, widest near
the top, and tapering to a point at the base. Segments
numerous, somewhat inflated, the peripheral ends ex-
tended into sharp points directed obliquely or horizon-
tally. Length, =+, inch (0°25 mm.).
B. robusta, nov.—Test elongate, compressed, broad and
rounded at the superior extremity, tapering to a point,
58 HENRY B. BRADY.
and frequently terminating in a long, stout spine at the
inferior end. Test thickest on the median line, and
sloping away symmetrically to the sides; margin sub-
acute. Segments numerous, about ten in each series ;
long, curved, obliquely set. Shell stoutly built, sutures
thickened, usually limbate and somewhat crenulate
externally. Length, #4 inch (0°6 mm.).
B. decussata, nov.—Test elongate, compressed ; broad and
obliquely truncate at the superior extremity, and taper-
ing to a rounded point at the inferior; margin thick,
square, or slightly rounded, lobulate. Surface beset
with low prominences or bosses, rounded or subangular
in outline, arranged with some regularity in oblique
rows, about four in each row, and entirely concealing
the septation. Length, 5 inch (0°dmm.).
B. Hantkeniana, nov.—Test depressed, equally convex on
the two faces; varying in contour, from a relatively
long form tapering to a point at the base, to broadly
oval one with rounded ends. Composed of numerous,
rounded, inflated segments, in two more or less regular
alternating series, surrounded by a delicate keel of
varying width and completeness. Surface often tra-
versed by short, delicate, longitudinal coste. The long
narrow specimens seldom have a continuous wing or
keel, and they attain a length of about =. inch
(0°9 mm.), whilst those of wider proportions with the
broader more regular wing are less than 5 inch long
(0°6 mm.) and about = inch (0°5 mm.) broad.
B. Karreriana, nov.—Test elongate, tapering, broadest near
the top, somewhat depressed ; inferior extremity pointed,
often mucronate ; margin thick and rounded, lobulate.
Surface of the test ornamented with numerous delicate,
often branching, or otherwise irregular, longitudinal
ribs. Segments inflated; aperture large, oblique.
Length, +; inch (0°63 mm.).
B. lobata, nov.—Test elongate, depressed, digitate; superior
extremity obliquely truncate or rounded, inferior obtuse.
Segments inflated, especially the later ones, their peri-
pheral margins subangular. Surface of the later cham-
bers more or less granulated. Sutures thickened, deeply
sunk. Aperture a long oval slit contracted at the
middle ; nearly central. Length ,); inch (0°4 mm.).
B. Schwageriana, nov.—Test oblong, biconvex, broadest
near the middle, tapering to a blunt point at the in-
ferior extremity ; margin carinate. Keel widest near
the middle of the shell, absent at the inferior end.
NOTES ON RETICULARIAN RHIZOPODA, 59
Sutures limbate, the limbation taking the form of raised
beads or irregular lines of shell-substance on both sides
of the test, chiefly near the points of contact of the two
opposing series of segments. Surface otherwise smooth.
Aperture large, with an oblique projecting tooth near
the superior end. Length, ; inch (0°56 mm.) ; breadth
near the middle of the test only slightly less.
B. amygdaleformis, nov.—Test oval, compressed, almond-
shaped; ends obtuse or rounded, periphery rounded.
Segments few; septation obscured by a surface orna-
mentation of stout, branching, longitudinal cost.
Terminal chamber nearly smooth and conspicuously
perforated ; aperture central, of long oval form,
slightly constricted at the middle. Length, = inch
(0°72 mm.).
B. subangularis, nov.—Test oblong, tapering, stoutly built,
more or less angular, somewhat concave or excavated on
both sides; inferior extremity obtusely pointed. The
angular contour is determined by the prominence of
superficial coste, the principal of which, six in number,
are placed, one down each lateral margin and two down
each face of the test. Aperture comma-shaped. Length,
=; inch (0°45 mm.).
Cass1DULiINA, d’Orbigny.
Cassidulina Parkeriana, nov.—Test crosier-shaped ; spiral
portion short, somewhat compressed, composed of few
segments arranged as in C. crassa; linear portion
straight or arcuate, cylindrical, biserial, the ends of the
segments overlapping alternately ; chambers short,
ventricose. Aperture comma-shaped, situated on one
of the lateral faces of the terminal segment, near its
apex. Length, ,, inch (0°57 mm.).
The Rev. A. M. Norman has a crosier-shaped species
in some respects similar to this, with the manuscript
name Cassidulina Bradyi, but the segments are long
and oblique, and the whole shell is compressed and
Vaginulina-like.
C. Jonesiana, nov.—Test oblong or ovate; external aspect of
the superior surface like that of a very thick Rotalian,
with slightly inflated chambers and rounded margin. On
the inferior face the umbilical ends of the chambers fall
short of the centre, leaving a deep cavity or depression,
from which the aperture proceeds, taking the form of a
curved, nearly erect slit, on the inferior face of the large
terminal chamber. Diameter, =; inch (0°7 mm.).
60 HENRY B. BRADY.
C. subglobosa, nov.—A large, thick, few-chambered, subglo-
bular shell; the dorsal margin gibbous and rounded,
the ventral less convex; aperture in the form of an
obliquely-set loop on the ventral face of the terminal
segment. Diameter, -,'; inch (0°7 mm.).
ENHRENBERGINA, Reuss.
Ehrenbergina hystrix, nov.—Shell somewhat ovate in gene-
ral form, the superior end broad and rounded. Segments
few, regular and alternate on the dorsal face, confused
on the ventral, their free ends terminating in lateral
spines. The sutural lines on the dorsal side marked
by rows of spines, sometimes fused into a fringe-like
projection from the shell-wall; the ventral surface of the
earlier segments also beset with stout spines or tuber-
cles. Aperture large, curved, situated in a depression
on the inflated face of the terminal segment, which is
ornamented externally with radiating lines, Length,
=; inch (0°75 mm.).
Lacena, Walker & Jacob.
Whilst the simplicity of the typical structure of Lagena
limits the range of variation in general form, it appears to
favour the production of an endless diversity of surface
ornamentation. It is impossible to recognise as “ species,”
or by any word of similar significance, the successive terms
of a series where every intermediate link may easily be
found ; nor is it easy under such circumstances to select the
points where the chain may best be broken to form groups
which have any approach to true specific value. In append-
ing names, therefore, to some of the more striking and more
easily defined modifications of the genus, it is to be under-
stood that they are no more than varietal or subvarietal
distinctions. Under these circumstances it has not been
thought necessary, at the moment, to do more than indicate
characteristic peculiarities, whether of contour or ornament.
Lagena botelliformis, nov.—Test unornamented ; long, cylin-
drical, of even diameter, arcuate, ends rounded ; entoso-
lenian. )
L. quinquelatera, nov.—A five-sided modification of L.devis ;
angles shar) or carinate ; surface unornamented or very
faintly striate ; ectosolenian.
L. stelligera, nov.—P yriform, ento- or ecto-solenian, with a
circular rim or collar at the base, one third the diameter
of the shell, and a number of short ribs (8—12) radiat-
ing from it.
NOTES ON RETICULARIAN RHIZOPODA, 61
L. longispina, nov.—A variety of L. globosa, either globular
or somewhat compressed, armed with long, stout spines
at the base.
L. unguiculata, nov.—Pyriform, compressed ; inferior end
broad and tapering to a thin edge, which is furnished
with a number of curved teeth set symmetrically.
L. samara, nov.—Test elongate, compressed, leaf-shaped,
tapering to a point at both ends; consists of a central,
circular, bi-convex chamber, with a large peripheral
wing, narrow at the sides, but much developed at base
and apex.
DL tubulifera, nov.—Chamber oval or pyriform, biconvex,
with long ectosolenian neck ; periphery furnished with
a broad laminar wing traversed by parallel or radiating
tubuli.
L. tubulifera, var. tenuistriata, nov.—A_ subvyariety of the
last-named, the body of the shell ornamented with
delicate longitudinal strie.
L. fimbriata, nov.— Compressed, broadest at the base, taper-
ing upwards; ento- or ecto-solenian; furnished with a
deep perpendicular wing or fringe running round the
oval base; the wing traversed by parallel tubuli.
L. auriculata, nov. (typica).—Pyriform, compressed _bilate-
rally, usually entosolenian ; on each side, near the base,
a loop-like wing encloses a portion of the peripheral
margin; or sometimes the whole periphery is bordered
by a wing which divides near the base, on each side, so
as to form a sort of loop. When the wing forming the
loop is deep it is usually tubulated.
L.. auriculata, var. substriata, nov., has, in addition, indica-
tions of riblets near the base and apex of the test.
LL. auriculata, var. costata, nov., has the body of the shell
strongly costate, and is frequently armed at the base
with short spines.
L. squamoso-alata, nov.—Body of the test like LZ. sguamoso-
marginata, P. & J., but with a further ornamenta-
tion consisting of a reticulated border and a broad
tapering wing with radiate marginal markings.
L. variata, nov.—Shape unsymmetrical, subglobular, gib-
bous, somewhat compressed, with an _ entosolenian
aperture at each end. Surface-ornament consisting of
irregular, slightly raised, rounded, longitudinal riblets.
LI. exsculpta, nov.—Shaped like LZ. globosa, or somewhat
compressed ; entosolenian. Surface-ornament consist-
ing of an excavated star radiating from the centre of
the inferior end. MRadii fluted, broad, and rounded at
62 HENRY B. BRADY.
the upper extremity, extending nearly half-way up the
test.
L. Wrightiana, nov.—Test oval flattened, with a thin peri-
pheral border, surmounted by a stout sessile phialine
lip; aperture entosolenian. Surface-ornament consist-
ing of a number of longitudinal, parallel, excavated
grooves covering the two sides, except the central por-
tions which are smooth.
L. favoso-punctata, nov.—Shape variable; surface-ornament
consisting of a raised reticulation, with an orifice or
perforation in the middle of each depression.
L. Schulzeana, nov.—Test oval, compressed, sub-carinate ;
sides flat; neck wide and yery short, finished with a
rounded lip. Surface-ornament consisting of transverse
bars, horizontal in the middle and bent downwards at
an angle, near the periphery.
L. trigono-ornato, nov.— General form similar to L. trigono-
marginata, P. & J. The peripheral angles are lim-
bate, reticulated externally, and much perforated.
L. plumigera, nov.—F lask-shaped, with long slender neck ;
surface-ornament consisting of ten to twelve longitudi-
nal coste, developed (especially at their lower ends)
into wide tubulated wings.
L. quadralata, nov.—F lask-shaped, ectosolenian ; furnished
with four equi-distant, broad, tubulated wings, reaching
from near the extremity of the neck to the base of the
shell ; the body of the test having an additional surface-
ornament of fine longitudinal strie.
L, torquata, nov.—Test flask-shaped with tapering neck.
Surface-ornament consisting of broad longitudinal costze
with depressions or perforations at regular intervals
down the centre of each; alternating with these are
narrower non-perforate ribs, and the whole are united
by secondary or less elevated crossbars.
L. Hertwigiana, nov.—Pyriform, with delicate ectosolenian
neck rising abruptly from the apex. Surface finely
reticulated, each angular mesh with a conspicuous per-
foration in the centre. Sections show that the shell-
wall is double, that the intermediate space is divided
into cells or chamberlets by perpendicular walls, of
which the external areolation marks the position, and
that the larger perforations open into the centre of the
cells. Length, > inch (0°34 mm.).
This is a particularly interesting species in its bear-
ing upon recently expressed views on the Dactyloporide.
Here, at least, is an undoubted hyaline Foraminifer
NOTES ON RETICULARIAN RHIZOPODA. 63
with a general aperture in a delicate transparent ecto-
solenian neck, and a cellular shell-wall like Ovulites,
each chamberlet provided with an external orifice.
Noposaria, Lamarck.
Nodosaria intercellularis, nov.—Test arcuate (Dentaline),
inferior extremity usually mucronate, composed of
about six segments, the earlier of which are sub-cylin-
drical, or only slightly inflated, the later ones ellip-
tical or pyriform. Surface-ornament of the earlier
segments. consisting of longitudinal coste; the later
chambers marked by lines of closely set perforations
which communicate with chamberlets formed in the
furrows between the ribs. ‘The structure of the later
segments closely resembles that of Lagena Hertwigiana.
Neck long, with annular or spiral raised ornament and
phialine or cleft lip. Length, -4; inch (1°6 mm.).
NV. abyssorum, nov.—Test stout, thick-shelled,nearly straight,
often irregularly built. Segments about five in num-
ber, subglobose, somewhat irregular in shape and size ;
primordial chamber, which is usually the largest, fur-
nished at its base with a number of short stout spines ;
neck short and broad, with large phialine lip. Length,
+ inch (2°8 mm.).
VaGINULINA, d’Orbigny.
Vaginulina spinigera, nov.—General form that of short,
broad, somewhat tapering specimens of V. leguwmen, but
furnished at the base with two (rarely three or more)
long stout spines, one of which is usually continuous
with the main axis of the shell, the others radiating at
various angles. Length of the body of the shell, inch
(3°5 mm.), the spines often two thirds as much, or even
occasionally as long as the shell itself.
Mr. Whiteaves has accurately described this form,! but
beyond alluding to it as a species of Marginulina, has not
given ita name. In one of the dredging lists published by
the late Dr. M. Sars, the name Marginulina spinosa occurs,
but without any description or other indication of characters,
and it is difficult now to say what was intended. So far
as the distinction between Vaginulina and Marginulina is
of any value, the species appears to belong to the former
rather than the latter genus; and as the want of a recog-
nised name for it has been a source of some inconvenience,
1 © Report Brit. Assoc.,’ 1872 ; ‘Trans. Sections,’ p. 144.
2 ¢Vidensk.-Selsk. Forhandlinger’ for 1868, p. 248.
64 HENRY B. BRADY.
it seems best to take this opportunity to supply the defi-
ciency.
CRISTELLARIA, Lamarck.
Cristellaria Siddalliana, nov.—Test spiral, explanate, with a
tendency to become centrifugal or crosier-shaped; ex-
tremely thin, usually surrounded by a broad, delicate
wing, except the septal or ventral face of the terminal
segment; the wing often extending between and sepa-
rating the last two convolutions of the discoidal portion.
Segments numerous, very slightly inflated, forming two
or more convolutions, the whole of which are visible on
both sides of the shell. Longer diameter, ~, inch
(1:26 mm.) or more.
C. gemmata, nov.—Test broad, oblong, compressed (Planu-
larian); earlier chambers spiral and embracing, later
ones broad and arcuate; each segment ornamented
with a row of exogenous heads either upon the sutural
lines or parallel to them. Length, J; inch (1°26 mm.).
PoLymorpPuina, d’Orbigny.
Polymorphina longicollis, nov.—Test long-ovate, subcylindri-
cal or fusiform ; segments few, erect, slightly ventricose,
the final one hispid externally, and terminating in a
long neck with phialine lip. Length, 3; inch (0°6 mm.).
An interesting intermediate link; the general characters
are those of Polymorphina, the neck and lip essentially
those of Uvigerina.
UvicERInA, d’Orbigny.
Uvigerina spinipes, nov.—Test elongate, subcylindrical,
slightly compressed on three sides; tapering to a point
at the inferior end, and armed with numerous spines
directed downwards. Segments inflated, distinct, some-
what irregularly combined. Length. = inch (‘77 mm.).
Saerina, d’Orbigny.
Sagrina columellaris, nov.—Test long, nearly straight, cylin-
drical, slightly tapering; inferior extremity round or
bluntly angular; superior, broad and convex. Uvige-
rine chambers few, distinct; uniserial segments nume-
rous, short, very little constricted at the sutural lines.
Aperture large, simple, with sessile phialine lip.
Length, =; inch (11 mm.).
S. bifrons, nov.—Test elongate, compressed, both sides
slightly concave along the median line; margin thick
NOTES ON RETICULARIAN RHIZOPODA, 65
and rounded. Uvigerine chambers few, distinct ; those
of the linear series numerous, short, not inflated.
Sutures flush externally; septa thickened by deposit of
clear shell substance. Aperture large, oval, surrounded
by a sessile lip. Length ;'; inch (0°84 mm.).
Discorspina, Parker & Jones.
Discorbina tabernacularis, nov.—Test conical or tent-shaped,
sides somewhat arched, inferior surface concave. Seg-
ments long, oblique, arranged in about three convolu-
tions ; septal lines externally limbate in small speci-
mens, in larger ones hidden by the general thickening
of the shell-wall. Inferior surface ornamented with
radiating striz or crenulations ; superior with striz or
irregular coste radiating from the apex. Diameter,
ty Inch (0°25 mm.).
In some localities specimens of D. tabernacularis are met
with in pairs, that is to say, two shells firmly attached
by their bases. The same condition is not unfrequent in
Discorbina pileolus, d’Orb., and D. Parisiensis, d’Orb.
TruncatuLtina d’Orbigny.
Truncatulina rostrata, nov.—Test biconvex, subnautiloid,
slightly unsymmetrical; periphery thin, subcarinate.
Chambers equitant; about ten in the final convolution,
which completely encloses the penultimate. Sutures
limbate, especially near the centre; marked by inden-
tations at the periphery. The true aperture is an
arched, labiate opening, placed transversely on the face
of the terminal segment, close to the margin of the
previous convolution ; but there is usually, in addition,
a second or spurious orifice, in the form of a vertical
slit in the beak-like projection of the peripheral angle
of the same. Diameter, =; inch (0°84 mm.).
Tr. Robertsoniana, nov.—Shell spiral, lenticular; superior
surface slightly convex; inferior convex, somewhat
depressed at the umbilicus; consists of four or more
convolutions, of which the whole are visible on the
superior face, whilst on the inferior the last whorl
conceals all preceding it, except a small area in the
centre. Segments very numerous, 13 or 14 in the
final convolution. Periphery angular, even, not con-
stricted at the sutures. Colour, rich brown, deepest
near the centre and at the sutural lines. Diameter,
3 inch (0°7 mm.).
VOL, XXI,—NEW SER.
66 HENRY B. BRADY.
Tr. margaritifera, noy.—Shell spiral; slightly convex or
nearly flat on its superior surface, convex on the infe-
rior; margin sharp, subcarinate, lobulate. Chambers
very numerous, all visible on the superior face, the last
convolution only on the inferior. Sutural lines on both
sides marked by rows of exogenous beads of clear shell-
substance, largest near the centre of the test. Diameter,
zy inch (1:26 mm.).
Tr. soluta, nov.—Shell elongate, compressed; composed of
a line of inequilateral segments, arranged spirally, the
earlier ones embracing, the later ones free. Periphery
sharp, furnished with a tubulated fringe or keel, and
the surface of the shell otherwise more or less orna-
mented with tubercles. Aperture a curved slit in the
line of the periphery at the extremity of the last cham-
ber, furnished with a phialine lip. Length, ~> inch
(0°36 mm.).
PULVINULINA, Parker & Jones.
P. procera, nov.—Shell spiral ; superior surface forming an
elevated cone with rounded apex ; inferior, flat or trun-
cate. Chambers numerous, about six in the last convo-
lution, oblique ; segmentation usually obscure, except
on the inferior aspect, where the sutures and periphery
are more or less limbate. Aperture, an arched slit on
the inferior side of the last segment, near the umbilicus.
Diameter, =; inch (1°1 mm.).
PoLysToMELLA, Lamarck.
Polystomella imperatriz, nov.—Test spiral, symmetrically
discoidal, complanate; peripheral margin rounded or
subangular, furnished with several (three to six) stout
spines. Septal ridges only slightly limbate, marked
with pitted depressions; retral bars very numerous,
delicate, irregular, sometimes branching. Diameter,
= inch (1°7 mm.).
P. verriculata, nov.—Test spiral, much depressed; sides
_ flattened; margin angular or slightly rounded. Septal
ridges and retral bars forming a coarse, more or less
regular, raised network, covering the surface of the
shell. Diameter, 3; inch (0°5 mm.).
CycLocLyPEus, Carpenter.
Cycloclypeus Guembeliana, nov.—A single specimen, nearly
complete, of a discoidal foraminifer referable to Car-
penter’s genus Cycloclypeus, and a fragment of a second
a ae
NOTES ON RETICULARIAN RHI1ZOPODA. 67
of the same species, were found in material dredged in
210 fathoms off Kandavu, one of the Fiji Islands.
Their structure is of much simpler type than that of
the gigantic discs dredged by Sir E. Belcher on the
coast of Borneo, which formed the basis of Dr. Carpen-
ter’s description of the genus. The better specimen is
a thin dise about +, inch (1°5 mm.) in diameter, some-
what biconvex; the convexity is chiefly in a limited
area near the centre of the test, the remainder being
thin, and tapering to a sharp edge at the periphery.
The texture is distinctly hyaline.
This little shell appears to represent the “ central
chambered plane” of the large forms, without the
thickened shelly plates on the upper and lower surface.
The chambers form a single layer, disposed in tolerably
regular annuli; in shape they are nearly square, not
elongate in the direction of the radii as in the larger
species, and the septal lines are slightly raised
externally.
I would suggest, for the sake of distinction, that the large
type, which, I believe, has never received a specific name,
should be called Cycloclypeus Carpenteri; that now des-
cribed I propose to name after Professor Giimbel, of Munich,
who has worked with so much success on the allied genus
Orbitoides.
3. Note on “ Biloculina-mud.”
In the second paper of this series,! some remarks were
offered upon the Foraminifera collected at or near the
surface of the ocean by means of the tow-net. A list was
given of the free-swimming species, so far as they were
known, and the question whether all the varieties of Godt.
gerina and the three or four pelagic species of Pulvinulina,
live exclusively at the surface of the open sea, was dis-
cussed. The recorded facts bearing upon the subject were
summarised, as well as the results of my own observatiuns,
not with the view of announcing any conclusions in the
matter, but chiefly in the hope of eliciting further contribu-
tions to the knowledge of a subject, concerning which there
was still much to be learnt. The question, from a zoolo-
gical stand-point, is now a comparatively narrow one. It is
not whether Foraminifera do live at the bottom of the sea,
1 “Quart. Journ. Mie. Sci.,’ vol. xix, N.S., p. 78, ‘Notes on Pelagic
Foraminifera.”
68 HENRY B, BRADY.
down to its greatest depths, for of that there can be no
reasonable doubt; it does not even affect the greater number
of types which are found in Globigerina-ooze, for of the forty
or fifty species or more which Globigerina-mud often contains,
those to which it refers may not exceed half a dozen, the re-
mainder being recognised on all hands as living their whole
life at the bottom. The point still in debate is, as already
indicated, whether a certain limited number of forms live
only at the surface, or also at various depths down to the
floor of the ocean; and it derives its chief interest and
importance from the fact that individuals of these few
species occur in such enormous numbers that in many areas
they constitute the mass of the calcareous deposit. The
cruise of the “Knight Errant” during the past summer
has in part removed one of the minor difficulties which were
put forward as negative evidence, by furnishing us with
surface gatherings of small non-spinous Globigerine from
an area in which they had not previously been collected,
and this is satisfactory as far as it goes: on the other hand,
the comparison of the surface and bottom specimens,
though not yet completed, appears to supply an argument
in the opposite direction. I do not propose at the present
moment to enter again upon the discussion of this subject,
though I hepe to revert to it at a future time; my object
is rather to offer a few notes upon the fauna of the sea-
bottom over an area in which the porcellanous Foraminifera
(Miliolide), which are known to be exclusively bottom-
living species, not only furnish the most characteristic
feature of the deposit, but form by far the most important
and bulky constituent.
Professor G. O. Sars, of Christiania, in his official report
on the Norwegian Sea-fisheries for the year 1876, gives a
short account of the biological conditions of the northern
*‘deep-water cold area,” which occupies a considerable
portion of the region between Norway, Bear Island, and
Spitzbergen on one side, and the Fardée Islands, Iceland, and
Greenland on the other. This region has a bottom tem-
perature of from 0° to 16° Cent. (32° to 34:9° Fahr.), and
the depth ranges from 300 to 2000 fathoms. The sea-bed,
especially of the deeper portions of the area, consists of a
soft, light-coloured, sticky mud, of nearly uniform composi-
tion; that is to say, composed in very large proportion of
one species of porcellanous Foraminifera, Biloculina rin-
1 “ Indberetuinger til Departementet for det Indre fra Professor, Dr. G.
O. Sars om de af ham i Aarene, 1864—-1878, anstillede Undersogelser
angaaende Saltwandsfiskerierne.” Christiania, 1879.
NOTES ON RETICULARIAN RHIZOPODA, 69
gens. Professor Sars has been kind enough to send mea
characteristic sample of this ‘‘ Biloculina-mud,”’ with the fol-
lowing particulars as to locality :
“Station 52—Lat. 65° 47:5’ N., Long. 3° 7’ W.; depth
1862 fathoms ; temperature at the bottom 1:2° Cent.’’ (about
34° Fahr.).
The fine impalpable silt had been partly removed
before I received it, I therefore completed the cleaning
by washing it thoroughly on a sieve of 120 meshes
per linear inch, through which no particles larger than
0:005 of an inch in diameter could pass. The loss was
about 6 per cent. of the entire weight, and, of the impalpable
material thus separated, about one half was calcareous, the
particles evidently consisting of the débris of foraminiferous
shells, and the other half fine silicious sand. I have no
information as to the proportion of impalpable mud in the
dredged material before the preliminary washing, but as
it is said to be sufficient to incorporate the whole into a
sticky paste, which on being dried forms a _ hard, light-
coloured, calcareous mass, it must be considerable. The
composition of the material as I received it from Professor
Sars was as follows—the proportions stated are by weight :
Biloculina ringens (one half being entire shells) . . 50p.c.
Haplophragmium subglobosum . : : eae,
Globigerine (the minute arctic form) . ‘ Ae
Sand and small fragments of rock with a few Forami-
nifera other than the above-named : a 20k bys
Impalpable débris_ : d : 5 : Seen
100
Assuming that the calcareous part of the impalpable
mud consists of the disintegrated shells of the same species in
similar proportions, the total amount of the deposit derived
from surface organisms would not in this case exceed 4 per
cent. even were Globigerine at all times pelagic.
The specimens of Biloculina are very uniform; they are
of the stout, inflated, typical form, with a small admixture
of the depressed carinate variety, B. depressa, d’Orb.
Hardly less remarkable is the existence of so large a pro-
portion of one of the comparatively small, nautiloid, arena-
ceous species, Haplophragmium subglobosum ; and here again
the specimens show scarcely any variation in minor char-
acters. The Globigerine are all of the minute, subglobular,
thick-shelled, arctic type, which may be fitly named Gi,
Dutertrei, var. borealis. Altogether sixteen species of Fora-
minifera were noted; but beyond those already alluded
70 HENRY B. BRADY,
to they were unimportant and represented by few indi-
viduals.
A sufficient number of apparently clean specimens of
Biloculina were selected for chemical analysis, but the
result gave a proportion of silica which suggested that not-
withstanding the careful washing to which they had been
subjected, the chamber cavities had retained a certain amount
of sand. The experiment, however, was sufficient to prove
that the tests contained no earthy carbonates except car-
bonate of lime, and no phosphates.
The analysis of Haplophragmium subglobosum was more
satisfactory, and as it is interesting to compare the chemical
composition of the test of one of the non-labyrinthic Litwole
with that of a labyrinthic type such as Cyclammina cancel-
lata, of which the analysis was given in a previous paper
(‘ Quart. Journ. Mic. Sci.,’ vol. xix, N.S., p. 25), I append
the details. As often heretofore ] am indebted to my friend,
Mr. J. T. Dunn, B.Sc., for practical help in the chemical
portion of the subject.
Haplophragmium subglobosum.
Silica . : : 3 : my Koni K(,
Peroxide of iron with some alumina 16:30
Carbonate of lime . : : Re ERD
99:70
The alumina was not separately determined, but as
it only exists in small proportion, the importance of pre-
oxide of iron as a constituent is evident ; and that the per-
centage is even larger than in Cyclammina is a noteworthy
fact. No phosphoric acid was present nor was there any
trace of magnesia.
In a recent letter, referring chiefly to the Biloculina
deposit, Professor G. O. Sars states that in the portion of
the Arctic Ocean lying east of the cold area already alluded
to, namely, east of Finmark, Bear Island, and Spitzbergen,
an entirely different bottom-fauna prevails. In this eastern
area the characteristic rhizopod is the large, stellate, arena-
ceous type Rhabdammina, which exists in such abundance
as to render the term “ Rhabdammina-ooze’’ not inappro-
priate for the dredged mud.
I can scarcely conclude these preliminary papers without
expressing the obligation I am under to some of my old
fellow-labourers in the same field of research. But for their
NOTES ON RETICULARIAN RHIZOPODA. 71
encouragement and ever ready help, the tedious details of
mechanical work which have occupied so much of my time
during the last four years or more, would have been weari-
some in the extreme. I hope in the proper place to make
due acknowledgment of many acts of courtesy that I cannot
enumerate here, and I will now do no more than mention
the names of Rev. A. M. Norman, Professor T. Rupert
Jones, Dr. Carpenter, and Professor W. K. Parker, as
amongst those to whom I am primarily indebted for assist-
ance and advice.
PostscRIPt.
Since the foregoing paper has been in print, I have received
through the kindness of Herr Gustav Steinmann, a copy of
his recently published memoir, “ Die Foraminiferengattung
Nummoloculina, n.g.” Without entering into any discus-
sion of the views therein expressed, I may just state that the
Nummoloculina contrarva of Herr Steinmann is in part, at
least, the Hauerina borealis of the present paper (p. 46).
The difficulty of distinguishing Hawerina borealis and
Biloculina contraria has been already alluded to, and if the
views put forward by Herr Steinmann be correct, is now
satisfactorily disposed of. At the same it must be remem-
bered, on the one hand, that between Biloculina sphera,
@Orb. and B. contraria, d’Orb. every gradation of form is
to be found in northern dredgings; and on the other, that
the alar prolongation of the chamber-walls is a character
shared by other species of Hauerina.
“I
wo
PROFESSOR A. MILNES MARSHALL.
On the Heap Cavitirs avd Assocratep Nerves of Etasmo-
BRANCHS. By A. Mitnes Marsnatt, D.Sc., M.A., Fellow
of St. John’s College, Cambridge. Professor of Zoology in
Owens College. (With Plates V and VI).
Tue discovery by Mr. Balfour! of the extension forwards to
the head of that splitting of the mesoblast which in the trunk
gives rise to the body cavity, and of the subsequent division
of the cavity so formed into the series of segments which he
has termed head-cavities, has given us a new and very impor-
tant clue to that favourite problem of morphologists, the seg-
mentation of the vertebrate head.
I have been led to pay special attention to the development
of these head-cavities in Elasmobranchs, in order to test the
accuracy of conclusions as to the morphology of certain of the
cranial nerves, notably the third pair, to which I had been led
by a study of their development in the chick.?
In the present paper I propose to treat of—(1) the develop-
ment of the head-cavities, (2) the relations of the cranial nerves
to these cavities, (3) certain stages in the development of those
nerves which are most intimately connected with the cavities,
and (4:) certain stages in the development of the eye muscles.
For my material, which consists almost entirely of embryos of
Scyllium canicula, | am indebted partly to Mr. Balfour and
partly to the Managers of the Southport Aquarium. With few
exceptions, the embryos were hardened in a + per cent. solution
of chromic acid, to which a few drops of a 1 per cent. solution
of osmic acid were added. In this solution they were left for
twenty-four hours, and then transferred to alcohol of 30 per
cent., which was gradually increased in strength until absolute.
In embryos prepared in the above manner, the brittleness due
to the use of osmic acid alone is completely avoided; all the
epiblastic tissues are stained a deep brown or black colour,
and the nerves in particular stand out with remarkable sharp-
ness and distinctness from the surrounding and but slightly
stained mesoblast.
Much of any success I may have obtained is due to this
mode of preparation, which appears to be peculiarly applicable
to nerve investigation. For a knowledge of the method I am
again indebted to Mr. Balfour.
The Development of the Head-Cavities.—As Balfour has
* *Elasmobranch Fishes,’ p. 206, seq.
* Vide this Journal, January, 1878, p. 23, seg.
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS, 738
already pointed out,' the separation of the layers of the meso-
blast so as to give rise to a ccelomic cavity, occurs much earlier
in the head than in the body. In the head this separation first
occurs in the earlier part of stage p,® while in the body in does
not commence till stages @ or H, though the two layers of the
mesoblast, somatic and splanchnic, are distinctly formed by
Stage D.
My observations on the earlier stages of development of the
head cavities accord so completely with the account given by
Mr. Balfour that I shall deal with the subject rather summarily,
referring the reader for a fuller account to Mr. Balfour’s work
already cited.
Plate V, fig. 1, represents a transverse section through the
head of a Scylliwm embryo at the end of stage c; the mesoblast
(mes.) is distinctly divided into two layers, which are just com-
mencing to separate from one another. Balfour figures a similar
section® at a slightly earlier age, when the mesoblast is one solid
mass with no distinction into layers.
By stage D this separation of somatic and splanchnic layers,
which is just commencing in fig. 1, has gone so far as to give
rise to a distinct cavity in the head region on either side, while
at a considerably later period (stages G or H) the separation ex-
tends further back, so as to form in the trunk the peritoneal or
body cavity.
The whole of the cavity so formed may be termed ccelom;
that part of it which is contained in the trunk is the body cavity,
while the anterior part, situated in the head, is named by Balfour
head cavity. This latter, as Balfour has pointed out,* “ can
only be looked on in the light of a direct continuation of the
body or peritoneal cavity into the head.”
Plate V, fig. 2, shows the condition of the head cavities at
stage H, as seen in a transverse section through the hind brain.
The cavities (4.c.) are of considerable size ; their ventral ends lie
against the sides of the alimentary canal (a/.), with which they
are in close contact, while dorsally they extend some distance up
the sides of the brain. The section also passes through the
roots (vit) of the seventh or facial nerves, whose distal ends are -
seen to be in very close contact with the dorsal walls of the head
cavities. The walls of the cavities are formed of a single layer
of short columnar or almost cubical cells.
The sections from the same embryo in front of the one figured
1 Op. cit., p. 86.
? Throughout the present paper I have employed, in order to distinguish
the different stages of development, the nomenclature proposed by Mr.
Balfour in his work cited above.
3 Op. cit., plate ix, fig. 2.
* Op. cit., p. 86.
74 PROFESSOR A. MILNES MARSHALL.
show that the cavities at this stage extend forwards beyond the
anterior end of the alimentary canal and end rather abruptly
immediately behind the outgrowths of the fore brain that give
origin to the optic vesicles. I have not found either at this or
any other stage any trace of a head cavity in front of the optic
vesicles. The cavities of the two sides are at stage H quite
distinct from one another, though their walls are very close
together anteriorly.
During stage @ a pair of lateral diverticula arise from the
alimentary canal, and form the rudiments of the first pair of
visceral clefts—the spiracular or hyomandibular clefts. These
diverticula, as they increase in size, first press the two layers of
mesoblast together, so as to obliterate the head cavities opposite
their points of impact, and then gradually displace the mesoblast,
the hypoblast of the diverticula ultimately coming into contact
with the external epiblast. After a short pause perforation of
the epiblast is effected, and the visceral cleft is completed. In
this way the head cavity on either side becomes divided into a
part in front of the hyomandibular cleft, and a part behind this
cleft.
Balfour’s account of the succeeding stages, which my own
observations simply confirm, is as follows :!—“ During stage 1
this front section of the head cavity (the part in front of the
hyomandibular cleft) grows forward and becomes divided, without
the intervention of a visceral cleft, into an anterior and a poste-
rior division. ‘The anterior lies close to the eye and in front of
the commencing mouth involution..... The posterior part lies
completely within the mandibular arch..... As the rudiments
of the successive visceral clefts are formed the posterior part of
the head cavity (behind the hyomandibular cleft) becomes
divided into successive sections, there being one section for each
arch. Thus, the whole head cavity becomes, on each side,
divided into—(1) a premandibular section; (2) a mandibular
section; (3) a hyoid section; (4) sections in the branchial
arches.”
The obliteration of the head cavity by the rudimentary visceral
clefts is well shown in Plate V, fig. 3, which represents a
somewhat oblique section, passing through the hind brain (A. 4.),
auditory pits (avd.), and third visceral (second branchial) clefts
(a/’) of an embryo of stage 1; 4.c. is the portion of the head
cavity left between the second and third visceral clefts, ¢.e. in
the first branchial arch ; a/’ is the diverticulum of the alimentary
canal which forms the rudiment of the third visceral cleft, oppo-
site which the two layers of mesoblast are seen to be brought
into contact so as to obliterate the head cavity ; and 4.c. is the
1 Op. cit., p. 206,
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS, 70
celomic cavity left between the two layers of the mesoblast
further back.
In the anterior part of the head the dorsal ends of the head
cavities are situated above the tops of the visceral clefts (vide
fig. 2) ; consequently, after these clefts are formed, the several
head cavities, while they are separate from one another below, still
communicate together dorsally. At the commencement of stage 1
the dorsal ends of the three anterior head cavities still com-
municate together, but between stages 1 and Kk they become
separated. ‘This point, which is not noticed by Balfour, appears
to be one of some importance, inasmuch as we have in this
division of the dorsal part of the head cavity a segmentation of
the mesoblast of the head, which is not directly caused by the
visceral clefts, although it takes place along the same lines, or,
more strictly, along dorsal prolongations of these lines,
The dorsal portions of the first three head cavities lying above
the level of the tops of the visceral clefts (vide Plate V, fig. 9,
1, 2, 3) become, at a still later stage, cut cff from the ventral
portions lying in the visceral arches. The subsequent changes
undergone by these dorsal and ventral portions differ mate-
rially from one another, as will be noticed later on. In the
trunk we also find a division of the coelomic cavity on either
side into a dorsai or vertebral portion, which forms a series of
cavities occupying the centres of the protovertebre, and a ven-
tral or parietal portion forming the peritoneal cavity.
It becomes now an interesting question, which, owing to
insufficient material, Iam unable as yet to answer definitely,
whether this division of the head ccelom into dorsal and ventral
portions is not strictly comparable to the division of the body
cceelom into vertebral and parietal portions. I have only
observed these dorsal portions in the first three head cavities—
the premandibular, mandibular, and hyoidean cavities.
“ Between stages 1 and k the anterior (premandibular) cavi-
ties of the two sides are prolonged ventralwards, and meet below
the base of the fore brain. The connection between the two
cavities appears to last for a considerable time, and still persists
at the close of stage u.”1 This median communication between
the two premandibular cavities is shown at stage L in Plate V,
fig. 13,1. Fig. 14 represents a longitudinal and vertical section
very near to the middle line, and shows the premandibular cavity
(1), still of considerable size. Fig. 13 represents the median
section from the same embryo; at 1 is seen the median com-
munication between the two premandibular cavities ; this is small,
but has a perfectly distinct and obvious lumen. This median
portion of the first head cavity has interesting relations to the
; ' Balfour, op. cit., p. 207,
76 PROFESSOR A. MILNES MARSHALL.
notochord and the pituitary body. As seen in the figure, the no-
tochord (z.) as it runs forward beneath the hind brain tapers
considerably. On reaching the level of the head cavity it
becomes still more constricted; it also leaves the floor of the
hind brain, becomes curiously twisted on itself, and, after running
forward a short distance in the mesoblast, bends sharply down-
wards and backwards, its terminal portion being very closely
applied to the dorsal wall of the head cavity. The figure also
shows that this median portion of the head cavity is in very
close relation both to the outgrowth from the fore brain to
form the infundibulum (af), and to the pituitary involution
from the mouth (pit.)
At stage these relations remain unchanged, the sole difference
being that the two walls of the head cavity have come in contact
so as to obliterate the lumen. By stage o the notochord has
lost its connection with the head cavity and now runs straight
forwards to its termination, while the walls of the head cavity are
reduced to a very thin cellular plate, lying in close contact with
the infundibulum and pituitary involution. I have not followed
the fate of this median cavity any further, and have not deter-
mined whether it forms any part of the adult pituitary body,
though, from its position, this would appear not improbable.
In fig. 23 this median portion of the first head cavity (J.) is
shown in horizontal section at a stage intermediate between L
and very shortly before its obliteration.
The premandibular cavity itself at stages k and 1 “ forms a
space of considerable size, with epithelial walls of somewhat
short columnar cells.” Its position and relations are well shown
in fig. 4, and in the series of figs. 8 to 14. It lies, as shown in
figs. 4 and 8, very close to the posterior surface of the eye (0. v.).
During stage m it becomes still more closely applied to the eye ;
it becomes partially doubled up on itself so as to form a hollow
cup, which closely invests the eye on its posterior and inner sur-
faces, as shown in figs. 18 and 20 (1), and figs. 34 and 35.
From the walls of this cup, as will be shown later on, certain of
the eye muscles are developed.
This premandibular cavity presents at certain stages a marked
constriction at its ventral part, tending to partially divide the
cavity into two; this is shown at stage 1 in fig. 9; and still more
clearly at a stage intermediate between ~ and m in fig. 21.
Whether this indicates an aborted division of this cavity into
two parts, each equivalent to one of the posterior cavities, or
merely a division into dorsal and ventral portions such as occurs
in the hinder cavities, J have been unable to determine.
The premandibular cavity persists very much longer than any
1 Balfour, op. cit., p. 206.
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS, 77
of the hinder cavities. Its more deeply situated portion is
shown in figs. 26 and 27, at a stage between m and n; and figs,
36 and 37 show that at stage o it not only persists but is con-
siderably larger than at the earlier stages.
The second or mandibular cavity presents during stages k and
L, as shown in fig. 5 (2), and in figs. 7 to 12, a dorsal dilated
portion, and (fig. 5) a laterally compressed ventral prolongation
extending down the whole length of the mandibular arch.
During these two stages the dorsal dilated end lies very close to
the surface immediately beneath the epiblast ; it lies at a more
superficial level than the cavities in front of and behind it, so
that in a series of longitudinal and vertical sections the most
superficial sections cut this cavity alone (fig. 7, 2); the subse-
quent ones cut all three cavities (figs. 8 to 10); while still
deeper ones cut the first and third only (fig. 12); and deeper
still only the median portion of the first (fig. 13).
By the commencement of stage m the mandibular cavity is
still but little altered (vide figs. 21, 22, and 23, 2); itis rela-
tively smaller, but still presents a dorsal dilatation and a flat-
tened prolongation extending down the mandibular arch. By
the middle or end of stage m the dorsal portion has atrophied
and disappeared; the prolongation into the mandibular arch per-
sists longer; its walls become converted into muscles,! but the
distal portion of the cavity still persists at stage o (vide fig. 34).
The third or hyoidean cavity is very similar to the second ; it
is from the first rather smaller, and situated, as already noticed,
at a rather deeper level. Its position and relations are shown at
stages K and 1 in figs. 4, 5, and 8 to 12 (3). It is also shown
between L and m in figs. 24 and 25 (3). Like the mandibular
cavity it presents a dorsal dilated part and a ventral laterally
compressed portion extending down the hyoidean arch. The
dorsal portion, like the corresponding part of the mandibular
cavity, disappears during stage m; the ventral part persists
longer, and its terminal portion is shown at the extremity of the
hyoidean arch at stage m im figs. 15 and 16. Its walls like
those of the mandibular cavity become ultimately converted into
muscles.
Relations of Cranial Nerves to Head Cavities.—Certain
of the cranial nerves have, as has already been shown by
Balfour, very definite and very important relations to the head
-cavities, and especially to the dilated dorsal ends of the three
anterior cavities. A full account will be given later on under
the headsof the seve ral nerves ; here I propose merely to note the
general relations.
1 Balfour, op. cit., p, 208.
78 PROFESSOR A, MILNES MARSHALL,
The main trunk of the seventh or facial nerve lies immediately
behind and in very close contact with the third or hyoidean
cavity ; this is shown in figs. 5, 8, and 9 (vir). Similarly the
maiu trunk of the fifth or trigeminal nerve lies wedged in
between the second and third, the mandibular and hyoidean
cavities, as is clearly shown in figs 5, 9, and 10 (vy).
The relations of these two nerves—the seventh and the fifth—
to the hyoidean and mandibular cavities are very definite, and
are very early acquired; they are fully established before the
close of stage 1, and have been already fully described by Bal-
four. They establish the fact that if the head cavities are to
be taken as indicating head segments, about which there can be
but little doubt, then these nerves must also be spoken of as
segmental nerves.
I now turn to a point of very considerable interest, which has
not, I believe, been noticed hitherto. Wedged in between the first
and second, premandibular and mandibular cavities, and occupy-
ing a position precisely analogous to that held by the fifth and
seventh nerves one or two segments further back respectively,
is a ganglion, shown in figs. 4, 10, and 11 (¢.g.). From this
ganglion a nerve can be traced forwards, figs. 13 and 14 (1m),
to the base of the mid brain. This nerve is conclusively shown
by its origin from the base of the mid brain, by its course, and
by its distribution, at a slightly later stage, to certain of the eye
muscles, to be the third or oculomotor nerve; while the gan-
glionic expansion on it, between the first and second head cavi-
ties, I believe I shall be able to prove, in a later section of this
paper, to be the ciliary ganglion.
I am not aware that the third nerve has been described by
previous observers in Hlasmobranch embryos, but if the figures
T here give of it be compared with the figures and descriptions I
have previously given of the development of the same nerve in
the chick,? it will be seen that the resemblance between the two
forms is of a very striking and conclusive character.
If the relations of the fifth and seventh nerves to the second
and third head cavities demonstrate the segmental value of
these nerves, then the relation which I have just pointed out the
third nerve bears to the first and second head cavities must also
be held to demonstrate the segmental value of this nerve.
Thave previously attempted, in my paper on the nerves of the
chick, referred to above, to prove that the third nerve is a
segmental nerve strictly equivalent to the fifth, the seventh, or
any other of the segmental cranial nerves. ‘The discovery that
the third nerve has, in Elasmobranchs, from a very early period
1 Op. cit., p. 197, seg.
2 This Journal, January, 1878, p. 23, seg, and Plates IZ and III.
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS. 79
of development, the characteristic relation to the head cavities
that is possessed by the fifth and seventh nerves, affords, perhaps,
the strongest possible confirmation of the segmental value of the
third nerve. Fig. 4 shows that this characteristic relation is
acquired by the third nerve at any rate as early as stage K.
I propose now to consider certain phases in the develop-
ment of these three nerves, the seventh, fifth, and third pairs.
My observations on the earlier stages are very fragmentary, and,
therefore, I shall omit for the present all account of their deve-
lopment previous to the latter part of stage 1.
The Development of the Third (Oculomotor) Nerve—t! have
not observed this nerve in specimens earlier than the commence-
ment of stage K; but by this time it is already a nerve of consi-
derable length, with its more important branches fully developed,
so that it must certainly be present at a considerably earlier
period. In the chick I have elsewhere shown! that the third
nerve is one of the first nerves, if not the very first nerve, in the
body to appear ; and my observations on Hlasmobranchs, though
inconclusive on this point, yet show no reason why the same
should not be the case in them.
In embryos of stage x the third nerve is a conspicuous and
easily recognisable object; it arises from the base of the mid
brain, not far from the mid ventral line, the roots of the two
nerves being only a small distance apart. Its root, which is
expanded somewhat, and has a triangular shape, contains nume
rous nerve-cells. From this ganglionic root (shown at stage L in
fig. 14 (az) the nerve runs as a long slender stem almost
horizontally backwards, then turns slightly outwards to reach
the interval between the dorsal ends of the first and second head
cavities, where it expands into a small ganglion (c. y., fig. 4).
From this ganglion two main branches arise; of these, one
(111 4, fig. 4) continues the course of the main stem of the nerve,
and runs down between the first and second head cavities; the
second branch (111 a, fig. 4) runs directly forwards from the
ganglion, passing along the top of the first head cavity, then
along the inner side of the eye, and finally terminates at the
extreme anterior end of the head, just dorsad of the olfactory
pit (off).
The ganglion (ce. g.) receives also a short but very interesting
branch (y. d., fig. 4) coming direct from the large ganglion at
the root of the fifth nerve. This communicating branch between
the third and fifth nerves is apparently that which is described
and figured by Balfour as the rudiment of the ophthalmic branch
1 Loc. cit., p. 27.
80 PROFESSOR A. MILNES MARSHALL.
of the fifth.’ I propose to consider it more fully in a later
section of this paper.
The condition of the third nerve and its branches at stage 1 is
shown in the figs. 10 to 12 and 14, representing longitudinal
and vertical sections at various depths of the same embryo. In |
fig. 10, the most superficial of these sections, the ganglion
(c. g.), is shown wedged in between the first and second head
cavities; the figure showing, in addition, the roots of the two
branches (111 @ and 111 4), already described, and also the posterior
half of the communicating branch (v. d.) between the fifth and
third nerves. In fig. 11, taken at a deeper level, the anterior
end of this connecting branch is shown. Fig. 14, at a still
deeper level, shows the end of the third nerve just before reach-
ing the ganglion; while, finally, fig. 14, which is the deepest
section of the series, not far from the midline, shows the greater
part of the length of the nerve, with the triangular ganglion at
its root of origin from the mid brain.
Towards the end of stage ut, besides this ganglionic root
of origin shown in fig. 14, two or three small additional roots
are developed ; these are very slender, are situated in front of the
main ganglionic root, and differ markedly from this root by
having no ganglion cells. Towards the end of stage 1, then, the
third nerve arises by one large ganglionic root and two or three
small, slender, non-ganglionic roots placed in front of the main and
original root. In stages Mm, N, and o, these small anteriorly
_ gituated roots become much more evident and also increase in
number; they are shown at stage o in fig. 40 (ar). The
morphological significance of these additional roots is discussed
later on.
The condition of the nerve between stages L and M is shown
in the series of horizontal sections represented in figs. 22 to
24. The section shown in fig. 22 is a curiously lucky one,
imasmuch as it includes the whole length of the third nerves
(am) on both sides from their origins from the mid brain to the
ganglia (e.g.) between the first and second head cavities. The
roots of the two nerves are seen to arise very close together
from the ventral surface of the mid brain ; each nerve runs for
a short distance almost directly backwards, then turns some-
what outwards, and runs to the interval between the first and
second head cavities (1 and 2), where it expands into the gan-
glionic swelling (c.g.). Fig. 23, taken at a rather more dorsal
level, shows the root of the third nerve on the right-hand side
and the ganglia (c.g.) on both sides, while fig. 24, at a still
more dorsal level, shows the communicating branch (v. d.)
between the ganglia of the third and fifth (v.) nerve.
' Op. cit., pp. 197, 198, and plate xiv, figs. 9 6 and 16 3.
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS, 81
The branches of the third nerve beyond the ganglion (c. g.)
are shown at stage m in the series of longitudinal and vertical
sections drawn in figs. 15 to 20; of which series fig. 15 is the
most superficial, and figs. 19 and 20 (which belong to opposite
sides of the body) the deepest. In fig. 20, the branches already
described are well seen. The ganglion (ec. g.) receives the com-
municating branch (v.d.) from the Gasserian ganglion on the
fifth, while from it proceed the branches 1a. and u14é. already
described at an earlier stage. Of these the anterior (111 @) runs
directly forward through the walls of the first head cavity (1),
then along or rather through the substance of the inner wall
of the eye, in front of which it continues its course straight
forward, as shown in figs. 19,18, 17, and 16 (im a), until it
ends, as seen in fig. 15 (11 @.), at the extreme anterior end of
the head, just dorsad of the olfactory pit (o/f).
The second branch (1m 4) from the ganglion (c.g.) is
practically the direct continuation of the main stem of the nerve;
it runs down, as seen in figs. 19 and 20 (a1 4), in very close
contact with the posterior wall of the first head cavity (the
second cavity having already disappeared). This posterior wall,
as will be fully described later on, 1s by this time converted in part
into certain of the eye muscles; and this branch of the third
nerve, which lies in close contact with these muscles (vide
fig. 19) and supplies them, ends in the most ventrally situated of
these muscles (0. 7., figs. 19 and 20).
At stage o the third nerve has still the same appearance, which
is indeed almost identical with that of the adult, as is shown
in the series of figures 33 to 40. Fig. 40, the deepest sec-
tion of the series, shows the large ganglionic root and the
smaller anterior non-ganglionic roots very clearly. From its
root the nerve can be traced running backwards and outwards
in figs. 38, 37, and 36, until it reaches, in fig. 36, the
posterior wall of the first head cavity. Fig. 35 shows the
branches (111 a) and (1m 4), also the communicating branch
from the fifth nerve; and in figs. 34 and 33, the terminal
branch (111 4) is clearly seen ending in the muscle (0. 7.).
On comparing the condition of the third nerve here described
in embryos from stage K upwards with that occurring in the
adult, there can, I think, be no doubt whatever that the ganglion
(c.g.) which lies wedged in between the first and second head
cavities is the ciliary ganglion. Professor Schwalbe has recently
pointed out, in a very important memoir on the morphology of
the ciliary ganglion, that it is really a ganglion belonging to the
main stem of the third nerve! He has shown that in Hlasmo-
' Schwalbe, ‘‘Ueber die morphologische Bedeutung des Ganglion
Ciliare,” ‘Sitzungsberichte der Jenaischen Gesellschaft ftir Medicin und
VOL, XXI.—NEW SER. F
82 PROFESSOR A. MILNES MARSHALL.
branchs, Amphibia, and some other forms, as the Crocodile, the
ciliary ganglion is in the adw/d situated in the trunk of the
third nerve, and has brought forward very strong arguments
for regarding this as the primitive position of this ganglion.
In Scyllium, as is evident from comparing Schwalbe’s figures
and descriptions of the adult! with the figures and descriptions
here given of embryos, there is practically no change in the
adult from the embryonic condition; in the adult, as in the
embryo, the ganglion is situated in the trunk of the third nerve ;
it is also situated in the adult in the very same position occupied
by the ganglion (c.g.) in the embryo, 7.¢. opposite the point
where the communicating branch from the fifth joins the third,
and where the third divides into the two branches (111 @ and
111 4).
Very strong evidence in support of the view advocated by
Professor Schwalbe is afforded by the development of the ciliary
ganglion in the chick. In the adult fowl the ciliary ganglion is
not situated, as it is in the dogfish, on the trunk of the third
nerve, but at the base of a short ciliary nerve arising from the
third nerve. In the embryo chick, at the end of the fourth day
of incubation, I have already figured? a ganglionic swelling on
the third nerve, exactly corresponding in position, relations, and
appearance with the ganglion (c.g.) of the Scy/diwm embryo. Pro-
fessor Schwalbe, in referring to my paper, has suggested® that this
ganglion, the existence of which has been somewhat gratuitously
called in question by Professor Kolliker,* is the rudiment of the
ciliary ganglion. I fully accept this suggestion of Professor
Schwalbe’s ; I had, indeed, arrived at the same conclusion pre-
vious to receiving his paper, and since then I have directed my
attention specially to the point, and have satisfied myself that
this ganglion, which in the embryo chick is situated in the trunk
of the third nerve (in the same position held by the ciliary
ganglion in both the embryo and the adult Scy//iwm) , becomes the
ciliary ganglion of the adult, which is no longer situated im the
trunk of the third but on one of its branches.
I think that this fact, that the ciliary ganglion of the chick
embryo occupies the position that it retains throughout life in
the Elasmobranchs and Amphibia, supplies the embryological
Naturwissenschaft,’ 15 November, 1878, and “ Das Ganglion Oculomo-
torii,”’ ‘Jenaische Zeitschrift fiir Naturwissenschaft,’ Bd. xiii. It is to
the latter paper, which is much the more complete, that I shall refer in
future.
1 Loe. cit., Taf. xiii, fig. 10.
2 Loc. cit., plate ii, fig. 22.
3 Loe. cit., p. 60.
4 « Entwicklungsgeschichte des Menschen u. der Hoheren Thiere,’ 1879,
622.
p-
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS, 83
proof necessary for the complete establishment of the view in
favour of which Professor Schwalbe has brought forward such a
mass of anatomical evidence, viz. that the ciliary ganglion is
primitively a ganglion belonging to the stem of the third nerve.
For a full account of the various modifications presented by the
ciliary nerves in adult Vertebrates I would refer the reader to
Professor Schwalbe’s very interesting memoir cited above.
On one point, however, I cannot completely agree with Pro-
fessor Schwalbe, z.e. when he says that the ciliary ganglion is
the homologue of a spinal ganglion.t That it corresponds in
part there can be, I think, no doubt; but it seems to me pre-
ferable to regard the ganglion at the root of the third, together
with the ciliary ganglion, and any intermediate ganglia that may
be found (for which vide Schwalbe’s paper) as collectively
equivalent to the Gasserian ganglion, or to one of the spinal
ganglia. I am disposed to view the third nerve as having been
abnormally pulled out and lengthened by the rapid growth of the
part of the brain with which it is connected, and to regard the
whole trunk, from the root of origin to the point of division at
the ciliary ganglion, as corresponding to the part of the fifth
bearing the Gasserian ganglion, and to compare any ganglia
that may occur on this part of the nerve to detached portions of
the Gasserian ganglion, isolated by the lengthening process which
the third nerve has undergone.
In naming and determining the other branches of the third
nerve, those I have marked 111 @ and 1114, I have been much
assisted by the very careful description given by Schwalbe of the
nerve in the adult Seyl/ium.
Schwalbe? describes and figures the third nerve in the adult
as giving off branches to the rectus superior and rectus internus,
then receiving at the ciliary ganglion a branch from the fifth
nerve, and then dividing behind the posterior border of the
rectus superior into two branches, of which the first passes
beneath the rectus inferior, supplying it with branches, and then
runs forward beneath the optic nerve to the obliquus inferior,
in which it ends. The second branch runs forward on the inner
side of the eye, piercing the sclerotic; it passes beneath the
rectus superior and obliquus superior, but over the optic nerve;
it leaves the orbit in front by a canal above the origin of the
obliquus inferior, and then runs forward to the anterior part of
the head.
This description and the accompanying figures show that in
Scyllium the third nerve has acquired by stage x all the principal
branches of the adult, and that these branches have also acquired
1 Loc. cit., p. 68.
* Loc. cit., pp. 15, 16.
84 PROFESSOR A, MILNES MARSHALL.
their characteristic course and relations. The communicating
branch from the fifth to the ciliary ganglion is undoubtedly the
branch I have marked v d. The first of the two branches into
which the nerve divides beyond the ganglion is the one marked
in my figure 1114, while the second of these branches, the one
which pierces the sclerotic, passes through the orbit, lying above
the optic nerve, and finally runs to the front of the head, is,
beyond all doubt, the nerve I have marked 11a.
The nerve 12a, which runs through the orbit beneath the
rectus superior and obliquus superior, and above the optic nerve,
is the nerve which, in many Vertebrates, receives the name ramus
ophthalmicus profundus of the fifth nerve. In most cases it
has the appearance of a branch of the fifth nerve; this appear-
ance I believe to be due to the communicating branch from the
fifth (v d.) becoming directly continuous with the anterior branch
of the third (111) and to the nerve thus formed losing its con-
nection with the ciliary ganglion. Should this conjecture prove
to be correct it will probably be found that in the early stages of
development the nerve mia is connected with the ciliary
ganglion, and that the connection is only lost comparatively
late.
Summary.—The third nerve, at stage K, arises from the mid
brain by a single ganglionic root; it runs back to the interval
between the first and second head cavities, where it expands into
a ganglion—the ciliary ganglion. This ganglion receives a short
communicating branch from the fifth nerve ; beyond it the nerve
divides into two branches, of which one continues the course of
the main stem, and ends in the oddiquus inferior, while the other
runs forward through the orbit, and is the nerve usually described
as the ramus ophthalmicus profundus of the fifth. My observa-
tions leave no doubt in my mind that in Scydlium this nerve is
really a branch of the third. Finally, in the later stages, a
number of slender non-ganglionic roots of origin appear in front
of the original ganglionic root.
The Development of the Fifth (Trigeminal) Nerve—At the
commencement of stage x the fifth nerve arises by a single root
on either side from the lower part of the side of the hind brain.
Immediately beyond its root of origin it expands to form a large
ganglionic swelling—the future Gasserian ganglion—the lower
part of which is wedged in between the dorsal ends of the second
and third head cavities. From this ganglion three branches
arise :—a. From the upper and anterior angle of the ganglion,
close to its root of origin, a nerve arises which runs forwards
and upwards and will be spoken of as the ophthalmic branch of
the fifth. 4. From the lower and anterior part of the ganglion
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS., 895
a nerve (v d., fig. 4) runs forward along the top of the second
head cavity to the ciliary ganglion of the third nerve (c. g.), this
being the communicating branch between the fifth and third
nerves already mentioned. c. From the most ventrally situated
part of the ganglion a nerve runs down in the interspace between
the second and third cavities, and is then continued down
in the mandibular arch; this may be called the mandibular
nerve.
Balfour describes only two branches of the fifth nerve at this
stage, of which the posterior is the mandibular branch of the
above description, whilst the anterior, which he describes and
figures* as lying in close contact with the upper wall of the second
cavity, and which he names the ophthalmic branch of the fifth, is
clearly the second of the three branches I have described above.
The first branch, to which, for reasons to be fully stated here-
after, I prefer to give the name ophthalmic branch of the fifth,
is not distinguished by Balfour from the second.
By stage u certain changes have occurred. In the first place
two or three new roots of origin are now present, which were not
recognisable at the earlier date. ‘These roots, which are well
shown in fig. 6 (vf), and also in fig. 11 (v/), are situated in
front of the original roots of origin; they are very slender, are
apparently variable in number, and differ materially from the
original root by being totally devoid of ganglion cells. Another
point of difference is that, opposite the ganglionic root of origin,
the brain presents a distinct external prominence or bulging,
well seen in figs. 6 and 11, while no such prominence occurs
opposite these new roots. These additional roots increase in
number during the later stages. By stage o one of them, usually
the most anterior, has become considerably larger than the others
(vide fig. 36, vf), though it still stands in marked contrast with
the original root by having no ganglion cells, and by not pre-
senting the external bulging of the brain at its point of origin.
These roots will be again referred to later on. I have been unable
to determine with certainty whether they arise as outgrowths
from the brain or from the ganglion.
By stage L an anterior branch—the maxillary nerve—is given
off from the mandibular nerve. This branch is also described
and figured by Balfour.
Fig. 5, shows the roots of the ophthalmic and the communi-
cating branches (v a. and v d.), and fig. 6 shows the ophthalmic
branch (v a.), as well as the two kinds of roots of origin at
stage L. Figs. 9 to 11 also show these branches in an embryo
of the same age.
Op. cit., p. 197.
2 Op. cit., plate xiv, figs. 9 6 and 16 4,
86 PROFESSOR A, MILNES MARSHALL,
The several branches of the fifth nerve are shown at stage M
by the series of figs. 15 to 20, of which, as already noticed,
fig. 15 is the most superficial, and fig. 20 the deepest. In
figs. 16 and 17 the maxillary (v 4.) and mandibular (vc.) branches
are shown very clearly ; these two nerves lie close to the surface,
though, as we shall see immediately, the maxillary is separated
from the surface by the palatine branch of the seventh. In
fig. 19 the communicating branch (v d.) between the fifth and
third nerves is shown lying at a deeper level than the maxillary and
mandibular nerves; it is a short nerve connecting the Gasserian
and ciliary ganglia directly together. The same figure shows
also two portions of the ophthalmic branch (v a.) of the fifth,
which runs forward close to the dorsal surface of the head and
immediately beneath the superficial epiblast. In fig. 20, taken
from the same embryo as fig. 19, but from the opposite side, the
root of the ophthalmic nerve (Vv a.) and the communicating branch
(v d.) are well seen; the latter is seen to give off a fine branch
(v e.), which runs upward to the muscle marked o. s.
Fig. 24 shows the roots of the ophthalmic and communicating
branches in horizontal section; the former (v a.) is seen to be
very close to the surface, while the latter (v d.) is situated
more deeply.
Figs. 26 to 30 represent a series of transverse sections
through the head of an embryo between stages m and wn; they
serve to illustrate the above description from a different point of
view. The sections are all slightly oblique, so that in each sec-
tion the left-hand half is in a plane a little posterior to the right-
hand half. Fig. 26 passes through one of the anterior non-
ganglionic roots of the fifth (v “), it also shows on the left
side the root of the ophthalmic nerve (va.), and the whole
length of the communicating branch (vd.) running to the
ciliary ganglion (¢c.g.). On the right hand side the ophthalmic
nerve (V a.) is seen in section.
Fig. 27 passes on the left side through the main or ganglionic
root of the fifth; on the right side it corresponds to the left side
of fig. 26. Fig. 28 shows on the left side the maxillary nerve
(v 4.) in nearly the whole of its length.
Finally, in figs. 32 to 35 the condition and relations of the
ophthalmic branch at stage o are shown; it is seen to be a
slender nerve running forward along the dorsal surface to the
fore part of the head, and giving off branches (fig. 32) on its
course.
Summary.—At stage kK the fifth nerve arises from the hind
brain by a single large ganglionic root , it expands into a large
ganglionic swelling, from which three nerves arise : (a), the oph-
thalmic branch, which runs along the dorsal surface to the
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS, 87
anterior part of the head; (b) the communicating branch run-
ning direct to the ciliary ganglion; (c) the mandibular branch,
which runs down between the second and third head cavities,
and then along the mandibular arch. By stage L two or more
slender non-ganglionic roots appear in front of the original gan-
glionic root, and the maxillary nerve is given off as a branch
from the mandibular.
The Development of the Seventh (Facial) Nerve——The
facial and auditory nerves at stage K arise by a single root
from the hind brain, a short distance behind the fifth nerve.
This root has the same ganglionic character as the original root
of the fifth, and has a similar bulging outwards of the hind
brain opposite its point of origin. The nerve divides almost
immediately into an anterior part—the facial, and a posterior—
the auditory nerve. The latter runs almost directly backwards,
and becomes applied to the anterior wall of the auditory vesicle
(figs. 7, 8, and 9 vitt awd.). The facial nerve gives off three
main branches: (a), from its upper and anterior part a very
large stout nerve arises, which runs forward along the dorsal
surface of the head to its anterior end, lying immediately above
the ophthalmic branch of the fifth, and immediately beneath the
superficial epiblast; this I shall speak of as the ophthalmic
branch of the seventh; (b) the second branch arises from the
anterior part of the facial nerve just below the root of the oph-
thalmic branch; this, which is also a stout nerve, runs down-
wards and forwards, lying parallel to and immediately superficial
to the maxillary branch of the fifth; it may be spoken of as the
palatine nerve; (c) the main stem of the seventh is continued
downwards as a stout nerve which runs along the posterior or
hyoidean border of the spiracular or hyomandibular cleft.
From this hyoidean branch an anterior or mandibular branch is
given off at a slightly later stage, which runs over the top of the
spiracular cleft, and then down in its anterior or mandibular
wall.
These branches of the seventh nerve are well shown at stage
M in figs. 15 to 18. The large ophthalmic branch (vita.) is
seen at its origin in fig. 17, while figs. 16, 18, 19, show other
portions of its course ; its relation to the ophthalmic branch of
the fifth (v a.) is seen in fig. 19. The root of this ophthalmic
branch of the seventh is also well shown at a slightly earlier
stage (between L and m) in fig. 25 (vita.), which shows how
very closely it lies to the surface. It is seen in transverse sec-
tion in figs. 26, 27, and 28 (vi1a.), and finally, is shown along
the whole of its course at stage o in figs. 32 to 35, these figures
&8 PROFESSOR A, MILNES MARSHALL,
showing its relation to the ophthalmic branch of the fifth (v a.)
particularly clearly. ;
The palatine nerve is shown at stage m in figs. 15, 16, and 17
(vir 6) ; it is a stout straight nerve, lying immediately super-
ficial to the maxillary branch of the fifth and very close to
this latter; these relations are still better seen in the trans-
verse sections shown in figs. 28 and 29; in both these
figures the two nerves (vi 4.) and (v 8.) are seen running
down side by side, and so close together as almost to touch
at places.
The hyoidean branch (v1 c.) is shown in figs. 15, 16, and 18 ;
and finally, the mandibular branch (vir d.) is well seen in
figs. 32, 33, and 34.
The seventh nerve is, in these stages, a very large nerve, very
much larger than the fifth ; two of its branches, the ophthalmic
and palatine, accompany branches of the fifth, the ophthalmic
and maxillary, very closely indeed, the branches of the seventh
lying in both cases more superficially.
Finally, the seventh nerve never acquires additional non-gan-
glionic roots of origin, such as have been described as occurring
in both the third and fifth nerves ; this is a distinction of some
importance and one to which I shall refer again further on.
Comparison of the Third, Fifth, and Seventh Nerves.—In
the section on the relations of these nerves to the head cavities
it has been shown that the third has the same right to be con-
sidered a segmental nerve that the fifth and seventh nerves have ;
and that it must, therefore, be regarded as a nerve of equal
morphological importance with the latter. It is, therefore, a
point of considerable importance to determine how far the
several branches of these three nerves can be compared with one
another.
All three nerves arise at first by single ganglionic roots; in
the case of the third and fifth additional non-ganglionic roots
are subsequently acquired, but in the case of the seventh no
such roots are acquired. I hope to show shortly that this
apparent distinction is capable of full and satisfactory expla-
nation.
Of the three nerves the seventh is very much the largest, the
third very much the smallest, the fifth, which is intermediate in
position, being also intermediate in size; this statement apply-
ing not only to the main trunk, but to the individual branches as
well.
In comparing the fifth and seventh nerves, there can be but
little doubt that the mandibular branch of the fifth corresponds
to the hyoidean branch of the seventh; and when we bear in
HEAD CAVITIES AND NERVES OF ELASMOBRANCHS. 89
mind that this branch in each case is the apparent direct ventral
continuation of the main trunk, and in the early stages in close
relation with the posterior wall of a head cavity, it will, I
think, follow that the branch (111 4.) of the third, which supplies
the rectus inferior and obliquus inferior, which is the apparent
direct ventral continuation of the main trunk of the third, and
which is in very intimate relation with the posterior wall of the
first head cavity, is the corresponding branch of the third nerve,
and is the strict homologue of the branches of the fifth and
seventh nerves mentioned above.
It would also appear probable, from the times of their appear-
ance and their general relations, that the maxillary branch of
the fifth and the mandibular branch of the seventh are equivalent
nerves.
Mr. Balfour, who was the first to describe the remarkabie
ophthalmic branch of the seventh,’ has already shown that it is
strictly comparable to the ophthalmic branch of the fifth.
Schwalbe? describes and figures the samusophthalmicus superficialis
in the adult Scy//iwm as arising by two roots, a posterior radix
dorsalis and an anterior radix ventralis or profunda ; these enter
the orbit by two separate foramina, run forward through the orbit
as the portio major and portio minor of the ramus ophthalmicus
superficalis, lying dorsad of all the eye muscles, and finally, on
leaving the orbit anteriorly, end in branches to the anterior part of
the head. As the two nerves (vii a. and v a.) in the embryo at
any stage from L upwards exactly correspond to this description,
there is, I think, no reason to doubt that these branches, which
I have called the ophthalmic branches of the seventh and fifth,
become respectively the portio major and portio minor of the
ramus ophthalmicus superficialis of the adult. Schwalbe’s figures
of the adult show that these branches acquire their final ar-
rangement at a very early period, in fact, from their very first
appearance ; his figure of these ophthalmic branches in the adult
represents, with almost perfect accuracy, their arrangement in
embryos of stage L. .
Balfour leaves the fate of the ophthalmic branch of the
seventh undecided,’ though he expresses himself as “ inclined
to adopt” the view of which I have attempted to demonstrate
the correctness.
There appears to be no branch of the fifth corresponding to
the palatine branch of the seventh ; this latter is a very singular
nerve, lying, as it does, so extremely close to the maxillary
branch of the fifth. I thought at one time that it might
E\Op. cit... p-199:
2 Loc. cit., p. 14.
3 Op. cit., p. 200.
90 PROFESSOR A. MILNES MARSHALL,
correspond to the buccal branch of the maxillary nerve, but its
independent origin from the main stem of the seventh seems to
disprove this.
The very remarkable communicating branch between the
Gasserian and ciliary ganglia still remains for consideration ;
concerning it we know—(a) that it is developed very early, (b) that
it is a direct connection between the main ganglia of the third
and fifth nerves. I have no direct observations on its develop-
ment, but am inclined to think it may be the remains of the
commissure which (at any rate in the Chick,’ and probably, also,
in Scylliwm) connects together, at an early stage, the rudiments
of the third and fifth nerves. This suggestion renders it neces-
sary for me to abandon the explanation | have previously given?
of the ophthalmic branches of the seventh and fifth nerves as
being possibly persistent rudiments of this commissure, as it is
obvious that the ophthalmic branch (v a.) and the communicat-
ing branch (v d.) could not both be derived from this com-
missure.
Concerning the anterior branch (111 a.) of the third nerve I feel
in great doubt. It seems possible that it may be an ophthalmic
branch of the third nerve, equivalent to the ophthalmic branches
of the fifth or seventh, and its course and distribution certainly
favour such a view. On the other hand, until the development
of the fourth nerve has been satisfactorily determined, I think
any attempt to determine the homologies of this branch of the
third would be premature.
The Development of the Sixth (Abducens) Nerve.—Plate
VI, fig. 38, represents a longitudinal vertical section through
the head of a Scy//ium embryo at stage o, the section being taken
a short distance to one side of the median plane; it shows the
three main divisions of the brain, the pineal gland (piz.) and
infundibulum, also the lateral expansion (ypzd.) of the pituitary
involution from the mouth. *Gratulationschrift an Fr. v. Rinecker,’ Leipzig, 1877.
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE. 99
In this animal the shape of the organ of Jacobson resembles
that of other mammals (see Jacobson and_Gratiolet) and of man,
as described by Kolliker, being a tubular structure flattened
from side to side, and leading in front into the ductus Steno-
nianus, which opens into the oral cavity; but its diameter is
much larger than that of the latter. It terminates behind in a
cecal extremity. It is surrounded, not by the bone of the
septum, but by hyaline cartilage. This latter is, however, alto-
gether independent of the cartilage forming the upper part of
the nasal septum. The cartilage surrounding the organ of
Jacobson, or Jacobson’s cartilage, forms a more or less com-
plete capsule around that organ. But there area great many
places where the cartilaginous capsule is incomplete, and then
the wall of the organ of Jacobson is in immediate contact with
the bone, or rather its internal periosteum. This incompleteness
affects more generally the lateral and lower than the median and}
upper parts. In some places the cartilage is reduced to a few
(one or two) small thin plates for the lower and median, and
two larger plates for the upper part of the organ. The car-
tilage always projects, for each organ, upwards as a plough-shaped
plate, showing an outer convex and an upper concave surface.
The connective tissue, 7.¢. the perichondrium, covering this
latter surface is at the same time the tissue by which the convex
lower border of the cartilaginous part of the nasal septum is
fixed here. Between the two there are in some places clumps
of fat-cells to be met with.
The measurements of the thickness of the cartilage of
Jacobson, where it is quite complete, as in the preparation
from which fig. 1, Plate VII, is taken, are these: just at the
middle of the organ of Jacobson, on either side, it is about 0:072
mm., at about its lower part 0:18 mm., at the upper or plough-
shaped part the diameter at its broadest part from side to side
is about 0°56 mm.; the diameter of the plough-shaped project
tion from the organ of Jacob soon the upper pointed extremity
of the former is about 0°72 mm. ‘The greatest transverse dia-
meter of the lower enlargement of the cartilaginous nasal
septum of fig. 1 is about 0°67 mm.
The description of the cartilage of Jacobson in the guinea-pig
here given differs from that given by Gratiolet of the mammals’
organ in general. His description is quite applicable to the rabbit,
as I shall show ina subsequent paper, for in this animal, “‘]’organe |
de Jacobson est entouré de cornet cartilagineux.”! In the rabbit
there exists a continuous broad slit along the upper part of the
wall of the organ of Jacobson, and through this slit the wall,
and especially its glands, form a continuity with the mucous
1 Loc. cit., p. 21,
100 DR. E. KLEIN.
membrane covering the cartilaginous nasal septum, but this
does not hold good in the guinea-pig.
Gratiolet speaks! of the tissue in that slit as of “ une sorte de
mesentere.” In the guinea-pig, however, the above-mentioned
plough-shaped projection of the upper part of the cartilage of
Jacobson includes one or two spacious longitudinal channels or
clefts for the branches of the nerves and blood-vessels supplying
the organ of Jacobson.
Figs. 1 and 2 of Plate VII give an accurate representation
of the relation of the cartilage of Jacobson to the organ of
Jacobson, and to the cartilaginous nasal septum. Both figures
were made with the camera, and their respective preparations were
obtained from the same organ of Jacobson at different places.
In fig. 1 the capsule is complete; in fig. 2 it is incomplete in
some places ; while in others the cartilage is reduced in thickness
to a very considerable degree.
Balogh,” in his description and illustrations of the cartilage of
Jacobson in the sheep, introduces a perfectly unnecessary and
complicated terminology of the different parts of the cartilage.
As far as I can understand his elaborate description (pp. 451
and 452), the cartilage does not differ much from that described
by Gratiolet of other mammals. Balogh does not know of
Gratiolet’s work, otherwise he might have been able to follow
this latter’s simple description.
As mentioned above, the organ of Jacobson is flattened, and,
therefore, its walls are generally considered as the lateral and
median wall, the latter being the one nearest to the median line
of the septum. For a better understanding we shall speak, in
addition, of an upper and lower sulcus, meaning the parts where
the lateral and median walls are in contact.
In the guinea-pig the outline of the transverse section is not
simply oval, but is kidney-shaped, the lateral wall being pressed
inwards, z.e. against the Jumen or cavity of the organ.
The size of the organ is about the same on both sides.
Gratiolet mentions, in the upper and outer part of the organ, a con-
spicuous projection, “un bourrelet saillant, que je ne saurais mieux com-
parer qu’al’organe décrit dans l’intestin du lombric sous le nom d’intestinum
in intestino.”
Balogh‘ finds in the organs of the sheep a similar projection of the wall
from the upper outer part, ‘ Drusenwulst.” But in the guinea-pig there is
no such projection from the upper part of the wail, the lateral wall as a
1 Loe. cit., p. 19.
2 « Sitzungsber. d. Kais. Akadem. d. Wiss.,’ Vienna, volume 42, p. 449,
“ Das Jacobson’sche Organ des Schafes.”
3 Loc. cit., p. 20.
$ Loc. cit., p. 457.
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE, 101
whole poems a slight convexity towards the lumen of the organ. Compare
Figs. 1 a
The following are the measurements of the different diameters,
taken at a point where the eartilaginous capsule is more or jess
incomplete at the outer and lower part of the organ (see fig. 2).
The short transverse diameter of the organ, exclusive
of the cartilage or bone, is about . : 0°7
The long transverse diameter of the organ, #. 2. ACTOSS
the t upper and lower sulcus is about. Berl TPR
The thickness of the lateral wall . ; ‘ : . 0°28 to 0°38 mm.
median wall . ; 5 Orb
The short transverse diameter of the cavity . 0:3
The long transverse diameter, from the ne, to the lower
sulcus . ‘ : : NW ae
The thickness of the wall at the lower sulcus is about the
same as that of the lateral wall, while that of the wall at the
upper sulcus is slightly larger than that of the median wall.
As regards the structure :
1. The lateral wall. This consists of (a) the epithelium lining
the cavity, (2) the subepithelial fibrous layer, (c) the layer of
the cavernous tissue, (d) the layer of the glands. Outside these is
the thin layer of fibrous tissue connecting the organ with the
cartilage, or, where this is wanted, with the bone, and acting as
the perichondrium or inner periosteum respectively.
a. The epithelium is in all respects similar to that lining the
mucous membrane of the nasal cavity, being composed of a super-
ficial layer of columnar or conical cells, between the extremities of
which extend spindle-shaped or inverted conical cells, z.e. cells
whose basis is directed towards the depth. Hach of these cells pos-
sesses an oval nucleus. The superficial conical cells show on their
free surface a bundle of fine cilia. The whole thickness of the
epithelium, inclusive of the cilia, is 0°064; the length of the cilia
is 0:0054 mm. Loewe! failed to see the cilia of the epithelium
of the lateral wall of the organ of Jacobson in the rabbit, but I
presume this is entirely owing to the mode of preparing the
specimens. Some of the superficial epithelial cells present them-
selves as goblet cells.
Leydig mentions’ that “ ciliated epithelium ” forms the boun-~
dary of the narrow lumen of the organ.
Balogh® does not distinguish, in the sheep’s organ, the epithe-
lium covering the lateral wall from that of the median wall, but
speaks of it as a whole, and remarks that it is ciliated |
epithelium.
1 ¢ Beitr. zur Anatom. d. Nase und Mundhoble,’ Berlin, 1878.
2 *Lehrbruch d. Histologie,’ p. 218.
? Loc. cit., p. 458,
102 DR, E, KLEIN.
b. A very delicate basement membrane separates the epithe-
lium from the next or the subepithelial fibrous layer. This
layer is chiefly composed of bundles of fibrous tissue, and in it
are capillary vessels, and here and there 4 thin bundle of un-_
striped muscle cells. ‘The thickness of this layer varies in dif-
ferent places ; in about the middle of the lateral wall it is about
0°032 mm.
c. The next outer layer is the layer of the cavernous tissue ;
/ this layer is thickest in about the middle of the lateral wall ; it
is altogether wanted near the upper and lower suleus. The
thickest diameter is about 0°12 mm. But at the places in
which the cartilage capsule is incomplete, the thickness of this
layer is much greater, being 0°22 mm. The length of this
layer varies between 0°43 and 0°61 mm.
The matrix of this layer is fibrous tissue, containing a plexus
of bundles of unstriped muscle cells. The essential parts are
large venous vessels connected into a plexus, the vessels running
chiefly parallel to the long axis of the organ, hence in a transverse
section most of them appear cut transversely. The transverse
diameter of the vessels varies between 0°046 and 0°092 mm.
Where the cartilage capsule is wanting, some of the vessels are as
large as 0°16 mm. in diameter. These vessels take up the
venous capillaries of the subepithelial fibrous layer as well as
some of those of the next outer glandular layer. The efferent
veins of the cavernous layer are smaller than the vessels of this
layer, a character essential of a cavernous tissue.
d. The layer of glands (Jacobson’s membrane adenoide, Gra-
tiolet’s membrane glanduleuse) is the next outer layer. It con-
sists of a wide-meshed framework of connective tissue, the
meshes containing the gland alveoli. A few nerve trunks are
met with amongst these latter in some places: from the caver-
nous layer extend small bundles of unstriped muscle tissue
amongst the alveoli in some places; a similar arrangement has
been pointed out by me (see October number 1880 of this Journal),
also for the glands of other parts of the nasal organ. This
layer is thickest at the lower sulcus, where its diameter amounts
to 0°22—0°28 mm. ; here it occupies at the same time the whole
thickness of the wall, there being here no cavernous layer. In
about the middle of the lateral wall the thickness diameter of
the gland layer is about 0°08 mm. It decreases towards the
upper sulcus, where it becomes reduced to a single layer of
alveoli.
In those places where the cartilage capsule is incomplete the
glandular layer is on the whole much better developed than
where this is not the case.
The gland alveoli are not confined to the lateral wall and to
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE, 103
the membrane at the lower sulcus, but extend at this latter
place also a short distance into the median wall.
There is a remarkable difference in the distribution of the
glands between the organ in the guinea-pig and the rabbit, in
this latter the glands being chiefly accumulated in the upper and
outer position, just as it is described by Gratiolet and Balogh.
The alveoli are branched and more or less convoluted tubes
of exactly the same nature as other serous glands, e.g. the parotid.
The transverse diameter of the alveoli varies between 0°024 and
0-036 mm. The alveoli are limited by a membrana propria ;
they possess a very minute lumen and are lined with a single
layer of polyhedral or short columnar epithelial cells, each
~~ with a spherical nucleus, situated in the outer part of the cell.
The cell substance is a dense reticulum, and therefore appears as
a uniformly granular protoplasm. The outline of the alveoli is
not smooth, but shows numerous minute, rounded prominences,
owing to some of the epithelial cells possessing a convex outer
surface. And it is just in these cells that the projecting convex
outer part of the cells, containing at the same time the small round
nucleus, appears more uniform and better stained than the inner
part, and hence the appearance is producéd very similar to
that presented by the cells of the alveoli of the pancreas.
The ducts are short and they take up directly the alveoli;
they are lined with a single layer of columnar epithelial cells; in
some instances the outer portion of the cell substanee- appears
longitudinally striated, just like those in the salivary ducts of
Pfliiger. The ducts open with a narrow mouth into the lower
sulcus, where the columnar ciliated cells of the lateral wall pass
into the mouth of the former. And these mouths form indeed
the boundary between the epithelium of the lateral and that of
the median wall. I have seen specimens (see fig. 5) where a
duct opening in the lower sulcus with a narrow mouth—about
0:012 mm. in diameter—became much distended behind this,
and extended in this state into the wall of the organ at the
lower sulcus to a depth of about 0°22 mm., the diameter of its
lumen being here 0:1; and throughout this whole length it was
lined with columnar ciliated epithelium, the length of the epi-
thelial cells being 0°02 mm., the length of their cilia about
0006 mm. In this same specimen from which fig. 5 is taken
Jacobson’s cartilage was wanting almost everywhere except at
the upper sulcus.
2. The median wall. As such will be considered that part of
the circumference of the organ which is not strictly limited to
the median line of the nasal septum, but which is covered with
a thick epithelium; this, owing to its peculiar nature, is the
‘ sensory epithelium,”
JO4 DR. E, KLEIN.
‘he median wall comprises much the greater half of the wall
of the organ, extending almost over two thirds of the whole
circumference. Its thickness is about 0°14 mm.; at the lower
sulcus it decreases slightly. The most conspicuous feature in this
is the sensory epithelium ; its thickness is 0°.l mm. What is
not epithelium, 7.e. outside this latter, is fibrous tissue inti-
mately connected with the perichondrium, or internal periosteum
respectively. Numerous small nerve-branches are contained in
the subepithelial layer, and here they may be followed as oblique
or longitudinal bundles, ultimately ascending into the sensory
epithelium. These bundles are derived from large branches,
which are contained as groups, and in company with blood-
vessels, in the channels of the plough-shaped upper part of the
cartilage above mentioned. Most of the nerve-bundles are
derived from the olfactory nerve, and, like this, are composed
of non-medullated fibres; but there are a few small bundles
of the nervous naso-palatinus of Scarpa. Gratiolet+ has very
|
exhaustively treated of the origin and distribution of these nerves.
As has been mentioned above, the gland alveoli at the lower
sulcus extend a short distance into the median wall.
The sensory epithelium extends over the whole of the median
wall proper, and the greater part of the adjacent sulcus superior
and inferior. Its structure is this: most superficially it, viz.
the epithelium as a whole, presents a faint vertical striation, the
strie being due to thinner or thicker granular-looking columnar
bodies. These, on careful examination with high powers, prove
to be either the thicker processes of the deeper cells reaching
up to the surface, or conical, thin epithelial cells, whose basis
forms part of the general surface. The conical cells are the
“ epithelial cells,” and they are smaller and thinner, and their
nucleus less distinct, than the epithelial cells of the olfactory epi-
thelium of the nasal cavity. Hach of these epithelial cells appears
to be possessed of a narrow, oval, transparent nucleus. Below
the layer of epithelial cells are several layers of spherical,
comparatively large nuclei, well outlined, and containing
a delicate reticulum. Hach of these nuclei belongs to a
spindle-shaped, granular-looking cell, of which one process, the
outer one, is broad, but thinner than an epithelial cell, and
extends as one of the above striz between the “ epithelial
cells,” up to the free surface, while the inner is very delicate,
and directed towards the depth. These spindle-shaped cells will
be spoken of as the “ sensory cells ;” the amount of all substance
around the nucleus is always appreciably larger than in the
olfactory cells”? of the olfactory region, with which they are
evidently analogous.
1 Loe. cit., p. 23 e¢ passim.
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE, 105
The sensory cells vary much in size, some being nearly twice
as bulky as others ; the latter possess also a larger nucleus than
the former. They are generally arranged in a number of layers,
five to twelve and more, either uniformly occupying the lower
half or two thirds of the whole epithelium, or they form
groups of four, five, and more. ‘There exists a great difference
in different parts as regards the extent to which the sensory cells
reach towards the surface, for there are many places in which
only a narrow strip of 0°027 (the whole thickness of the epithe-
lium being 0°1 mm.), z.e. only a fourth of the whole epithelium
is free of them, while in other places they occupy a layer of
0054 mm., or about one half of the whole epithelium. But it
must not be therefore supposed that in the latter places the
epithelial cells are much longer than in the former; this is
not by any means the case; in the places where the sensory
cells reach up near to the surface, the “ epithelial cells,’ if not
wholly absent, are reduced in numbers to a very great extent,
the outer processes of the sensory cells almost entirely occupying
their places. Towards the sulcus, superior and inferior, the
epithelium as a whole decreases in thickness; at the sulcus the
epithelial cells become very few, and the sensory cells almost {
entirely form the layer. There exists a most sharp boundary
between the sensory epithelium and the ciliated columnar epithe-
lium of the lateral wall, as mentioned above. The sensory
epithelium at the extremities of the median wall is either rounded
off, or it terminates with a pointed margin. On the free sues
of the sensory epithelium is a delicate cuticle, similar to the cuti-'
cle of v. Brunn, in the olfactory region. Both the processes of
the sensory cells ana the basis of the epithelial cells appear to
project over the cuticle, the former as a very minute rod-like,
and the latter as a minute knob-like, homogeneous process.
Amongst the lower layers of the sensory epithelium are seen
either small bundles of nerve fibres, or isolated fine fibres, both
extending in an oblique direction. The termination of the yy
nerves has not been ascertained. =
On the whole, then, this sensory epithelium corresponds to
the olfactory epithelium, except that, in the latter, there exists a
deep layer of inverted conical “‘ epithelial cells,” ¢.e. cells, whose
bases are fixed on the subepithelial basement membrane. In the
sensory epithelium of the organ of Jacobson this deep layer of
inverted conical epithelial cells is apparently wanting, the sen-
sory cells reaching as far down as the subepithelial fibrous coat.
Besides, as mentioned above, the “ epithelial cells” of the sen-
sory epithelium in the organ of Jacobson are much more in-
distinct and smaller than those of the olfactory epithelium,
106 DR. E. KLEIN.
while the bodies of the sensory cells appear larger than those
of the olfactory cells.
Balogh? describes the epithelium of the organ of Jacobson of
the sheep, without, however, making a distinction between the
sensory epithelium lining the median wall and the ciliated epi-
thelium lining the lateral wall. According to this observer the
epithelium consists of two kinds of cells—(a) large ciliated
columnar cells, and (2) smaller olfactory rods (Riechstibchen).
These latter are rod-like, hyaline, and contain in their lower or
deeper part a swelling produced by the nucleus. They extend
to the free surfaee, and possess here two triangular pointed rods
(Riechhirchen).
Balogh says that he has convinced himself of the connection
of the epithelial cells with the processes of the connective-tissue
corpuscles of the mucosa, while the ‘‘ olfactory rods” are con-
nected, through spindle-shaped cells, with the olfactory nerves.
But, considering the methods with which he worked (macera-
tion in acetic acid mixture) it 1s not too much to say that these
assertions must be received with great reserve.
I cannot say precisely what the function of the organ of
Jacobson is, since I have not made any experiments on this
point. Kdlliker? thinks that “if we do not assume that the
tubes of Jacobson are simply secretory organs, their vascular
thickness, their numerous glands, and the numerous branches of
the nervus naso-palatinus, seem to point to it; but against this
speaks their supply with very numerous olfactory nerve-fibres.
There remains nothing else but to assume that they (Jacobson’s
tubes) secrete yuices and substances which act on their specific
nerves, and thus enable the organism, directly, as it were, to
obtain knowledge of the chemical constitution of its own juices.”
Whatever may be the precise meaning of this view of Kolliker’s,
it seems strange to have recourse to such a theory. Why should
it not serve for the perception of specific smells, seeing that it
really belongs to the olfactory nerve termination? Its commu-
nication with the oral cavity does not appear to me to be adverse
to such an assumption.
In man the organ of Jacobson is only of a rudimentary
nature (Kolliker) as compared with that of mammals, and do
not these latter possess a power of perception of smell, about the
degree and nature of which human beings can hardly have a true
conception ?
1 Loe. cit., p. 465.
+ Dog. Cites ps LL.
x
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE, 107
Il.—Zhe Accessory Organ of Jacobson.
At 8, in fig. 1 of Plate VI, a minute tube is shown in transverse
section, which extends alongsidethe groove which, at the bottom of
the nasal cavity, is contained between the septum and the alveolar
process of the superior maxilla. This tube is shielded, as is shown
in the figure, partly by the lower extremity of the osseous lamella
that forms the support of the lower conchanarium. It, z.¢. the
tube, is met with as far as the tube of Jacobson extends, and like
this is bilateral. I will call it the “accessory organ of Jacobson ;”
it is also flattened from side to side, and it includes a lumen
varying in diameter, in hardened specimens, and in different
places. In some places the lumen is a narrow slit, in others it
is of relatively large transverse diameter. The wall of the tube
consists of an epithelium and of a loose connective tissue, which
above and below is thickest, and includes here a plexus of large
vessels, arteries, and veins, extending chiefly in a longitudinal
direction, @. e. parallel with the tube.
The following are the measurements of the accessory organ,
the epithelium only being here considered as the wall of the
tube :—At a place exactly corresponding to that in fig. 1, the
tube being much compressed from side to side, I find the breadth,
t.e. the transverse diameter of the tube from side to side—lumen
and epithelium of both sides—amounts to 0°144 mm., while the
height of the tube, z.e. the transverse diameter across the upper
and lower wall, is 0°63 mm. .
At another place, further backward, where the tube appears of
larger size, and with a much larger lumen, the breadth of the
tube (lumen and epithelium of both sides) is 0°518 mm., while
the height is 1:06 mm., the transverse diameter of the lumen
being 0°38 mm.
The epithelium lining the tube is stratified columnar epithe-
lium, whose thickness is somewhat greater in the median wall,
z.e. the wall nearer the nasal septum, than in the lateral wall.
In the upper and lower sulcus it is slightly thicker than at the
sides. At a place identical to that represented in fig. 1 the
thickness of the epithelium of the median wall is 0-079 mm.,
that of the lateral wall 0°058 mm. At a place further in front,
‘2.é. where the tube appears larger, the thickness of the epithe-
lium of the median wall is 0:05 mm., of that of the lateral wall
0-04 mm.
The epithelium lining the iumen is the most conspicuous, and
at the same time the thickest part of the wall. On its inner
surface, i.e. the one facing the lumen, there exists a well
marked cuticle, similar to that mentioned in the organ of Jacob-
108 DR. E. KLEIN.
son. The epithelium consists of a superficial layer of conical
epithelial cells, about 0:032 mm. long, each with an oval
nucleus ; their free basis, which is on the surface, appears covered
in some places with fine cilia, similar to those described above
of the lateral wall of the organ of Jacobson. Both in the lateral
and median wall I have seen in some places indications of fine
cilia still connected with the surface of the épithelial cells, while
in others there were no cilia in connection with the cell bases,
but there were minute rods and cilia-like bodies near the surface
of the cells held together by a mucous coagulum. From this it
appears probable that the cilia have become detached from the
surface of the cells. In some places a great many of the epithe-
lial cells are converted into goblet cells, with or without mucus
in their interior.
Away from the surface the cells are drawn out into a single
or branched fine process. Between these are packed-in spindle-
shaped cells, each with a spherical or slightly oval nucleus. In
some places, especially in the median wall, these spindle-shaped
cells are very conspicuous, there being a considerable amount
of protoplasm around the nucleus, but in other places they
appear very minute. Underneath these cells and forming the
inner or lower boundary of the epithelium is a stratum com-
posed of one or two, or in some places of the median wall,
even three, layers of small spherical or oval nuclei, closely placed
side by side; to each nucleus belongs a very narrow zone of
protoplasm, hence the nuclei form in this stratum the most pro-
minent part. They are more deeply stained than the nuclei of the
other cells. Their cell protoplasm is of a polyhedral or conical
or angular shape, but is always inconsiderable.
In some places of the upper and lower sulcus the spindle-
shaped cells are much more numerous than the other cells, and
hence the appearance is produced not unlike that of the sensory
epithelium of the organ of Jacobson.
Branched lacunz are seen extending from the subepithelia
membrane into the epithelium itself, where fine canaliculi pass
from the lacunz between the individual epithelial cells, 7. e. into
the interstitial cement substance. These lacune and their cana-
liculi are best seen in oblique or horizontal sections through the
epithelium of the tube, and they correspond to the lymph-cana-
licular system known of the epithelium of other membranes.
One of the most striking appearances is the presence, in about
the middle of the epithelium, of spherical or oval cavities; each
of them appears limited, and consequently separated, from the epi-
thelial cells by a very delicate membrane, and hence may be spoken
of as an intraepithelial vesicle, the smallest of them being about
0-014, the largest about 0-05 in diameter. They occur ina single
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE, 109
layer only, both in the lateral and median walls ; but towards the
upper and lower sulcus their number is much diminished. In
those parts where the tube is larger; e.g. in the front part, the
number of these vesicles is greater than where the tube is smaller.
Where they are most numerous they are situated so closely
that they are separated from one another by epithelial masses,
whose breadth is not much greater than that of themselves, 7. e.
the vesicles. The dome of these vesicles, z. e. the surface nearest
the lumen of the tube, is covered with the columnar superficial
epithelial cells only ; they are here less of a conical but more
of a cylindrical shape, and shorter than the cells of other places.
Above the middle of the dome the epithelial cells are reduced
to about 0:016 mm. in length, ze. half the length of the
conical cells of other places.
Each of these vesicles is connected with the internal lumen
of the tube by several minute canals extending between the
epithelial cells forming the dome up to the free surface. With
the subepithelial membrane the vesicle is connected by a ver-
tical or slightly oblique channel. This latter is much larger
than the ones leading into the inner cavity, and may be appro-
priately spoken off as at the neck. Its breadth is measurable ;
it amounts to 0:005 mm., while its length is about 0°02 mm.
The deep stratum of small epithelial cells, described above, is
partly invaginated by the passage through it, of the neck
of the vesicle, the small cells not reaching further than the
point of connection of the neck with the vesicle. The neck,
together with the vesicle, resembles a flask-shaped organ; the
former contains, and is, in fact; filled with a cord-like continua-
tion of the subepithelial membrane, and it consists of a tissue,.
in which occasionally a capillary blood-vessel, a few spindle-
shaped looking cells, or a nerve-fibre can be recognised. This
tissue is continued into the vesicle, but fills only a small part of
the cavity of this latter. In some rare instances I have seen
two vesicles connected by a horizontal broad channel. The
vesicles and their neck could be compared with the papille of
other membranes, but this comparison would not be quite
correct, inasmuch as in an ordinary papilla, the epithelium, as
a whole, is inflected over this latter, whereas in our present
instance the flask-shaped vesicle penetrates, as it were, into the
layer of the epithelium.
The case of the penetration of capillary blood-vessels and
pigmented cells into the epithelium of that portion of the liga-
mentum spirale, known as the stria vascularis in the cochlea, could
be perhaps more appropriately adduced, and is in a certain sense
similar to our own case. A penetration of capillary blood-vessels
110 DR. E. KLEIN.
into the epithelium has been described by Professor Lankester! in
the integument of the medicinal leech.
Outside the epithelium is a fibrous coat, whose thickness in
the lateral and median wall is about the same, 0°05—0°06 mm.
It contains minute nerve-bundles, and eapillaries are found only
immediately underneath the epithelium. In the lateral wall
there are several arterial vessels running longitudinally ; where
the organ is in contact with the bone (see fig. 1), the fibrous
coat is in intimate connection with the periosteum. In the
lower part of the median wall, z.e. the one in contact with the
mucous membrane of the descending inner surface of the concha
(see fig. 1), the mucous membrane is more or less distinctly infil-
trated with lymph-cells similar to that of the concha. At the
upper and lower sulcus the tissue is very loose, and contains, as
mentioned previously, large blood-vessels running in a longitu-
dinal direction ; the diameter of the largest vessels here is about
0-13 mm. Numerous elastic fibrils, extending longitudinally
and connected into a network and flattened connective-tissue
cells, each with an oval nucleus as well as a few minute nerve
branches, are also to be met with here.
1G EP:
The mucous membrane covering the cartilaginous septum
and lining the furrow between the septum and the alveolar
process of the superior maxilla in the region of the organ of
Jacobson has the following structure :—Both surfaces of the car-
tilaginous septum are lined with an epithelium of exactly the same
nature as that described above as lining the lateral wall of the
_organ of Jacobson, viz. stratified columnar epithelium, of which
the most superficial cells are conical and possessed of cilia.
Goblet cells occur also here.
The thickness of the whole epithelium is about 0°056—0:07
mm., the length of the cilia 0:006 mm.
The mucous membrane immediately underneath the epithelium
is fibrous connective tissue, infiltrated in many places with lymph-
corpuscles. A network of venous vessels in the mucous mem-
brane forms a very conspicuous feature.
The mucous membrane of the septum is thickened at three
definite places, owing to the presence of glands; these places
are: a, where the septum joins the dorsum of the nose; 4, in
about the middle height of the septum; and ec, at the point
where the thick rounded lower margin of the cartilaginous
septum is fixed on the cartilage of the organ of Jacobson. In
Plate VII, fig. 1, these places are easily recognised. At the last
place the thickening is greater than at the second, and at this
1 This Journal, No. 79, New Series, p. 303.
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE. 111
greater than at the first. The thicknesses of the mucous mem-
brane of the three places in the preparation from which fig. 1
is taken are 0°25, 0°29, 0°36 mm.
The glands are serous glands; there are no other glands here.
Their structure is identical with that described above of the lateral
wall of the organ of Jacobson. The alveoli are tubes, wavy and
convoluted, some more branched than others; their transverse
diameter is about 0:02 to 0°036 mm.; their lumen is very
minute, and they are lined with a single layer of columnar or
polyhedral, granular-looking cells, the nucleus of which is
situated in the outer part of the cell.
The ducts are identical with the intralobular ducts in the
salivary glands, 7. e. Pfliiger’s salivary tubes; their epithelium is
a single layer of beautiful columnar cells, whose outer portion is
conspicuously longitudinally striated ; their nucleus is spherical,
and contained in about the middle of the cell.
The lumen varies between 0°0135 and 0:019, the whole dia-
meter of the duct, including the entire epithelial wall, being
between 0°04 and 0:05 mm.
The cartilage of the septum is hyaline, but the cartilage cells
show this peculiarity, that in many places they contain minute
fat-globules. In some places they are quite filled with them,
and in specimens that have been prepared with osmic acid the
cartilage cells appear then filled with black spherules. When
dissolving away the fat-globules the honeycombed reticulated cell
substance becomes very evident, and is identical in appearance
with that presented by the epithelial cells of the alveoli of the
‘sebaceous and Meibomian glands.
The groove between the septum and the alveolar process of
the superior maxilla is lined with a thin mucous membrane, the
free surface of which is covered with the same ciliated columnar
(stratified) epithelium as the septum.
Small groups of alveoli of serous glands are found in very few
places. ‘The tissue of the mucous membrane is infiltrated with
lymph-corpuscles ; in the outer wall of the groove, 7. e. on the
alveolar process of the superior maxilla, these infiltrations amount
occasionally to a distinct lymph-follicle (see fig. 1,13). The ade-
noid tissue of the lymph-follicle penetrates into the epithelium of
the surface, in the same way as is seen in the summits of the
lymph-follicles of the Peyer’s glands and on the tonsils. I
measured one such follicle, oval in shape; its long diameter is
about 0°28 mm., its short diameter 0°16 mm. The follicle lies
close to the epithelium ; this latter is here much infiltrated with -
adenoid tissue, but, on the whole, thinner by about one fourth
than the ciliated epithelium of the neighbourhood.
112 DR, E, KLEIN,
IV
The mucous membrane covering the concha or turbinal bone
differs in structure from the one hitherto described in the follow-
ing points :—As is shown in fig. 1 beginning from a, 7.e. imme-
diately after passing the region of the accessory of Jacobson’s
organ, the mucous membrane as a whole becomes thicker, owing
to their being contained in it a continuous layer of serous
glands. Its thickness diameter amounts here to about 0°25
mm. But the epithelium becomes thinner (see at a, in fig. 1),
being now composed of a superficial layer of short columnar
cells without cilia, and a single deep layer of small polyhedral or
conical cells. From a to 4, in fig. 1, the epithelium retains the
character just described ; its thickness is between about 0-016
and 0°024 as against 0°056, the thickness of the stratified
columnar ciliated epithelium downwards froma. In the prepara-
tion from which fig. 1 was taken the epithelium altered its
character at 2 ; from here over c to d, the epithelium is stratified
pavement epithelium, consisting of a superficial stratum corneum
like that of the epidermis, and a deep stratum Malpighii, con-
sisting of two or three layers of polyhedral cells. Indications
of minute papille are met with here. The whole thickness of
this stratified pavement epithelium is between 0-016 and 0-024;
the superficial stratum corneum is about 0:008 mm. thick.
Where the stratified columnar epithelium joins the stratified
pavement epithelium it is seen that, just as in other similar
regions, the superficial cells of the former become suddenly
shorter and are continued on the pavement epithelium as the
superficial layer of scales.
But not in all places does the stratified pavement epithelium
commence at 4; in some places the columnar non-ciliated epi-
thelium may be followed up to ¢, being, however, in one or two
places interrupted by short islands of stratified pavement epithe-
lium ; beyond ¢, z. e. up to d, the epithelium is always stratified
pavement epithelium.
Near the epithelium the tissue of the mucous membrane con-
tains a plexus of large veins, chiefly running longitudinally, and
the membrane is in many places infiltrated with lymph-corpuscles.
The thickness of the mucous membrane at about J and ¢ varies
between 0°14 and 0°18 mm.; between ¢ and d its thickness is
0:14 to 0°3 mm. From a to d the mucous membrane includes
a continuous layer of serous glands; they are here short tubes,
generally branched and more or less convoluted. Their duct is
also very wavy, and it passes in a very oblique or almost horizontal
direction towards the surface, where it opens with a wide mouth,
into which the surface epithelium is continued for a short dis-
MINUTE ANATOMY OF NASAL MUCOUS MEMBRANE. 113
tance. Where there is on the surface stratified pavement epi-
thelium, the stratum corneum above mentioned is also continued
for a short distance into the duct, as I have mentioned in my
paper in the October number of this Journal, 1880.
The ducts possess a relatively large lumen, and are lined with
a single layer of columnar cells, whose outer part is very conspi-
cuously striated, and whose nucleus is spherical, and situated in
about the middle of the cell; they resemble, therefore, com-
pletely the salivary tubes of Pfluger. The diameter of the
ducts varies between 0:048 and 0°06 mm., the lumen being
between 0°012 and 0:024 mm. The structure and size of the
alveoli are in all respects identical to those described above of
the aveoli of the serous glands of the other parts.
In some places the layer of these serous glands is much
thicker than in others; in such cases there are bundles of un-
striped muscle cells to be traced between the alveoli, forming in
some places a plexus, and acting then as the matrix of the gland
alveoli. The large veins, mentioned above, appear in this case
also embedded in a tissue containing unstriped muscular tissue,
and hence the appearances are produced not unlike those of a
cavernous tissue (see my paper in this Journal, October, 1880).
I have given an illustration of these relations in the ‘ Atlas of
Histology,’ plate xlvi, fig. 20.
VOL, XXI.—NEW SER. H
114. DR. E. KLEIN.
Histotocicat Notes. By BH. Krein, M.D., ¥.R.S., Lecturer
on Histology and Embryology in the Medical School of
St. Bartholomew’s Hospital.
DissEctine the salivary glands of the guinea-pig I noticed
various points in their arrangement and structure which I do
not think have been observed by others, and therefore deserve to
be described.
Removing the skin of the facial and cervical regions the
salivary glands present themselves in the following arrangement :
1. The parotid occupies the position as in the rabbit, dog,
cat, and other mammals; it is very flat, its lobules loosely con-
nected and scattered over a considerable area. Its colour and
structure is the same as in other mammals. The lower part of
the parotid, z.¢. in the region of the angle of the inferior
maxilla, but not specially marked off from the rest of the gland,
is much thicker, and extends as a compact body, of about
15—20 mm. in length and 10 mm. in breadth, in a transverse
direction.
Fixed to the posterior margin of this oblong thickened
portion, but surrounded by its own connective-tissue capsule,
is a small, oval, and somewhat flattened, whitish-looking body.
Its length is about 8 mm. its breadth 5 mm. and its thickness
between 2 and 3 mm. Its structure is identical with that of
the submaxillary of the dog, that is, it is a mucous gland. The
intralobular ducts are, like the salivary tubes of Pfltiger, lined
with columnar epithelial cells, whose outer portion is conspicu-
ously fibrillar. The alveoli are branched and convoluted tubes,
their relatively small lumen is lined with a single layer of
columnar mucous cells of the ordinary description. There is,
however, this distinction between.the gland under considera-
tion and the submaxillary of the dog, that there are no cres-
cents in the alveoli of the former. I have carefully searched
for them but failed to find them.
In a gland in which the ducts appear filled with a granular
secretion the mucous cells of the alveoli show more or less
distinctly two zones, an outer and an inner zone, the latter more
transparent than the former. In a former paper (this Journal,
April, 1879) I have called attention to a similar differentia-
tion in the mucous cells lining the alveoli of the submaxillary
of the dog.
The efferent duct lies on the side next the parotid, whose
large ducts it joins.
Claude Bernard saw occasionally small mucous glands con-
~
HISTOLOGICAL NOTES. 115
nected with the duct of the parotid of the dog. Heidenhain
(‘ Hermann’s Handbuch d. Physiologie,’ V Band, p. 25) says
that in the parotid gland (of the dog) he met with alveoli
lined with mucous cells, but, he adds, this occurrence is not
frequent.
2. Passing from the parotid along the inner side of the lower
jaw we meet with a large gland, of a pale rosy colour, compact,
oval, or rather pear-shaped, and holding the position of the sub-
maxillary gland of other mammals. Its length is 15—20 mm.,
its breadth in the part nearest the parotid is much greater than
that of the other end, in the former being about 10 mm., in the
latter about 5 mm., its thickness is about 5 mm. Now, the
structure of this gland coincides neither with that of the parotid
of this or other animals, nor with that of the submaxillary
gland of other mammals, for it is identical with that of the
pancreas.
Boll (‘Archiv f. Mikr. Anat.,’? Band v), describes the submaxillary
gland of the guinea-pig as a mixed gland, 7.¢., its alveoli are in some
places lined with mucous cells, in others with protoplasmic cells like
those of the parotid. Lavdowsky (‘ Archiv f. Mikr. Anat.,’ Band xiii, p.
286) denies this, but neither here nor on the following page (287), on
which he gives a tabular classification of the various salivary glands of
man and mammals, does he say of what nature the submaxillary of the
guinea-pig is.
The alveoli are branched and convoluted tubes showing great
inequality im size; their very minute lumen is lined with a
single layer of colmmar or pyramidal cells, in each of which,
just as in the pancreas, can be distinguished an outer and an
inner zone ; the former contains the spherical nucleus, and stains
well in hematoxylin and carmine, while the latter looks granular
and transparent, and does not stain. The former, 7. e¢. the outer
part, contains rod-like structures, which in some cells are very
much coarser than in others. These rods are arranged longi-
tudinally, and are distinct only near the membrana propria. I
do not find, however, the centroacinar cells of Langerhans. The
structure of the intralobular ducts is the same as in the sub
maxillary gland.
It will be of great interest to inquire whether the secretion
of this gland is similar to that of the pancreas.
Close to the outer capsule of the gland is found occasionally
a minute oval lymph-follicle, ensheathed in its own connective-
tissue capsule; its long diameter is about 0°6 mm., its breadth
0:18 mm. The surface of the lymph-follicle is not smooth,
being notched-in at two or three places.
Attached to the posterior, or rather inner margin of the sub-
maxillary gland, but contained within its own connective-tissue
116 DR. E. KLEIN.
capsule, is an oval whitish gland, in size, aspect, and structure
perfectly identical with the gland mentioned above in connection
with the parotid; and it is this gland which has been noticed by
Bermann (‘ Dissertat. Wiirzburg,’ 1878) as the tubular (mucous)
gland in connection with the submaxillary gland of the guinea-
pig, rabbit, and other mammals.
I propose to call these two glands, viz. connected with the
parotid and the submaxillary, as the admaxillary glands, and to
distinguish the former, z.e. the one connected with the parotid,
as the upper or superior, the latter, 7.e. the one connected with
the submaxillary gland, as the lower or inferior admavxillary
gland. As a rule, I find the inferior gland in the position
mentioned above;! in one instance (that of an animal three to
four weeks old), it was found on one side more or less buried
between the lobes of the submaxillary, and on the other side
it could not be detected on the outer surface at all.
Measuring the diameter of the alveoli in sections through the
resting glands of the same animal, hardened in spirit and stained
in carmine, I find the transverse diameter of the alveoli of the
parotid about 0°027 mm. and less; that of the alveoli of
the admaxillary glands about 0°054 and more; and of the sub-
maxillary gland about 0:04 mm.
Measuring the cells lining the alveoli of the same three
different glands just mentioned, I find the following to be the
mean sizes :
a. In the parotid, the cylindrical cells are 0°010 mm. in
length, 0:007 in breadth; the pyramidal cells 0-010 in length,
0:009 in breadth next the membrana propria, 0:0036 next the
lumen.
6. In the admaxillary glands, the cylindrical cells are 0°0198
mm. in length, 0°01 in breadth; the pyramidal cells 0°018 in
length, 00136 in breadth next the membrana propria, 0:0036—
0:0054 next the lumen.
e. In the submaxillary gland, the cylindrical cells are 0°0162
mom. in length, 0°009 in breadth; the pyramidal cells 0°0144 in
length, 0-007 in breadth next the membrana propria, 0°003 next
the lumen.
3. Attached to the front part of the submaxillary gland, and
partly covering it, and often extending close to the parotid, is an
oval whitish body; this is the thymus gland. As is well known,
the guinea-pig does not possess a thoracic thymus; but the gland
that I mentioned just now as situated bilaterally close to the
submaxillary gland is found iz the young as well as in the adult
1 The position of this gland is not, however, constant, for in one
instance I found it on one side in front, on the other at the inner margin
of the submaxillary.
HISTOLOGICAL NOTES. TE
animal. In both instances its structure is the same. In the
adult its length is about 11 mm., its breadth about 7 mm., and
its thickness between 2 and 8 mm. The size of the gland does
not vary much in the young and adult animal, and, owing to its
position and lobulated nature, cannot be easily distinguished on
the naked-eye inspection from the salivary glands. Its structure
is identical with that of the thymus of other animals, and like this
consists of the connective tissue forming the capsule and the pro-
longations of this into the interior as septa between the lymph-
follicles. These latter are oblong, conical, cylindrical, or irre-
gular in shape; they are of very various sizes, and their surface
is either smooth: single follicles, or they are lobed, owing to
more or less deep furrows, variable in number (two, three, and
more up to ten), passing into the interior of the follicle: com-
pound follicles. Where these furrows extend deep into the
interior, the appearance is produced of a follicle being possessed
of a number of secondary follicles, of very various sizes and
shapes, and all projecting from the main body of the follicle. This
appearance can be also interpreted by saying that a number of
follicles have become more or less fused together.
As regards the size of the follicles, it is difficult to make exact
measurements, owing their very irregular shape. The following
measurements are taken from a vertical section through the
gland :
One of the very large compound follices: length, 3°15 mm. ;
breadth, 1:0].
Another large follicle: length, 2°92; breadth 1:23 mm.
A very small follicle, the length, 1:01—1:23; breadth,
0°68 mm.
In a horizontal section, the length of a large follicle 2°7, the
breadth 1°23 mm.; of a small one, the length 0°92, breadth
0°53 mm.
As regards the structure, the follicles completely coincide
with those of the thymus. As in these, the outer part of the
follicle z.e. the cortex of Watney, both in the single follicles as well
as in the secondary projections of the compound follicles, stains
deeper than the central part, z.¢. the medulla of Watney, which
is non-transparent, and includes fewer small lymph-corpuscles
than the former ; the medulla contains, like that of the follicles
of the thymus in other animals, larger cells, with one, two, or
more large clear nuclei, such as have been known previously,
and have been more minutely investigated by Afanassiew
(‘Archiv f. Mikr. Anatom.’ Band xiv), and Watney (‘ Proceed-
ings of the Royal Society,” No. 187, 1878). Also the concentric
bodies of Hassall are found in the follicles of the thymus in the
guinea-pig. ‘Their structure is the same as of those described
118 DR. E. KLEIN.
by Afanassiew (‘Archiv f. Mikr. Anat.,’? Band xiv, 3rd_ part).
Seeing that these concentric bodies occur in all the glands of
adult animals that I have examined, and seeing that the struc-
ture of the follicles remains the same, 7.e. their tissue does not
undergo the fatty and connective-tissue degeneration that always
occurs in the follicles during the involution of the thymus gland
in other animals, it follows that Afanassiew’s view of the
degeneration of the follicles being caused, or rather initiated, by
the concentric bodies cannot be sustained.
DIGESTION AND ENDODERM OF LIMNOCODIUM. 119
On the INTRA-CELLULAR DicEsTION aud KNpoperM of Limnoco-
pium. By HK. Ray Lanxester, M.A., F. R.S. With Plates
Wir, 1X.
No observation made within the last three years appears to
me to have greater importance and general significance for the
progress of Biology than the discovery of the inception of solid
food particles by endoderm cells im the Planarians and Nemato-
phorous Ceelentera, by Elias Metschnikoff.
The actual history of this discovery appears to date from the
observations of Lieberkiihn on Spongilla (‘ Miiller’s Archiv,’ 1857).
The first observer to suggest the existence of intra-cellular
digestion in an organism other than one of the Protozoa or of the
Porifera, was Allman, who, in his memoir on Myriothela (‘ Philo-
soph. Transact.,’ vol. 165, 1875, p. 552), describes a thin layer of
protoplasm as occurring on the free surface of the endoderm,
and observes that “its occurrence, with its pseudopodial exten-
sions, on the gastric surface of the animal, is full of interest, and
suggests a close analogy between the absorptive action of the
gastric surface and amceboid reception of nutriment.”
Next we have a note by Metschnikoff in the ‘ Zoolog.
Anzeiger,’ 1878, p. 387, in which the inception of solid food
particles by the cells lining the alimentary canal of certain
Planarians is described, and in the ‘Zeitsch. wiss. Zoologie,’
1879, p. 371, the same author describes similar observations
on Sponges.
Led by these observations of Metschnikoff, Jeffery Parker came
to the conclusion that a similar mode of digestion obtains in
Hydra. In his paper on the histology of Hydra fusca, published
in the ‘Proceedings of the Royal Society,’ 1880, and in this
Journal, April, 1880, Parker carefully describes the amceboid
character of the endoderm cells of Hydra as seen in sections,
the extent and activity of their movements during life having
been previously insufficiently recognised. Dark-coloured irregu-
lar granules of various sizes are found within these cells, and
were noted by Kleinenberg to vary in number with the state of
nutrition of the animal. Parker is convinced that these bodies
are food particles, taken into the protoplasm of the cells, from
the partially disintegrated bodies of the Entomostraca in the
digestive cavity. The clearest case of ingestion of solid particles
observed by Parker was when a diatom was seen to be com-
pletely embedded in the protoplasm of a cell. Parker very
judiciously observes that it is quite possible that a preliminary
120 FROFESSOR E. RAY LANKESTER.
disintegration of the animals taken in is performed by juices
secreted by the endoderm cells; but the final digestion seems to
take place in the actual protoplasm of the cells, into which the
food particles are taken in the solid form. He does not suggest
how the digested material is distributed to the other cells of the
Hydra.
asi, we have a brief réswme from Metschnikoff in the
‘Zoolog. Anzeiger,’ No. 56, May, 1880, of a series of observa-
tions on the subject of intra-cellular digestion, carried on by him
in the spring at the Zoological Station at Naples.
Metschnikoff made use of carmine powder, which he observed
to penetrate the endoderm cells in many Hydroid polyps and
Hydromedusee (Plumularia, Tubularia, Eucope, Oceania, Tiara,
Praya, Forskalia, Hippopodius, Pelagia, Beroe among Cteno-
phora and Sagartia and Aiptasia among Anthozoa.) In the
Trachymedusee Liriope, Carmarina, Cunina, Metschnikoff failed
to establish the occurrence of intra-cellular digestion. It will
be observed that the method employed by Metschnikoff is not
altogether a conclusive one. The majority of forms studied by
him, like the Hydra studied by Parker, are opaque, and, conse-
quently, it was not possible to watch the process of ingestion
during life. In Praya, however, Metschnikoff studied a trans-
parent form, and was able to observe the throwing out of
pseudopodia by the endoderm cells, and their fusion into a
plasmodium. ven here, however, it seems that there is still
room for doubt as to whether the pseudopodia are really active
in digestion, for Metschnikoff only speaks of their penetration
by carmine particies. It is exceedingly probable that when his
observations appear at greater length, we shall find that they
include the fact of inception of natural food materials, such as
Alge, disintegrated Entomostraca, &c. The mere penetration of
minute particles like those of powdered carmine into amceboid
cells would not in itself indicate a natural process of intra-cel-
lular digestion. Such a penetration of carmine particles into the
amceboid corpuscles of vertebrate blood is well known, and does
not in that case lead to the inference of normally occurring
intra-cellular digestion.
On this account I think some importance attaches to the
observations which I made last summer on the intra-cellular
digestion of Limnocodium, the fresh-water Medusa discovered
in the lily-house of the Botanical Gardens, Regent’s Park,
London. I was able, in this animal, on avcount of its exceeding
transparency, to study the endoderm cells during life, and to
establish the fact of the inception of natural food materials
by those cells.
I have since made a careful study of the endoderm of various
DIGESTION AND ENDODERM OF LIMNOCODIUM. Ibe |
regions of this Medusa’s body in specimens preserved in osmic
acid.
The series of questions which arise in connection with this
phenomenon of intra-cellular digestion are so numerous and
important that it is quite certain that the most complete study
of the endoderm of the various regions of the digestive tract is
necessary before the phenomenon can be rightly appreciated.
The following considerations, amongst others, are those which
naturally present themselves to an observer as indications
directing his inquiries.
PRELIMINARY CONSIDERATIONS.
1. Supposing it to be established that some of the endoderm
cells in Hydroid and Anthozoan polyps are capable of ingesting
solid food particles, the question arises whether this is an occa-
sional and accidental phenomenon, or whether it is a normal
and definitely fixed function of such endoderm cells.
2. The question also occurs as to whether all the endoderm
cells have this property, or whether it is limited to certain groups
of these cells, whilst a distinct kind of activity (possibly similar
to that of the gastric cells of other animals) is assigned to other
cells in the same animal.
3. Further, it is of fundamental importance to ascertain what
becomes of food particles ingested by ameboid endoderm cells.
Are these particles digested by these cells as food particles are
by an Ameeba? or are they again ejected unchanged.
4. Supposing the food particles to be digested—that is to say,
dissolved and converted into diffusible peptones or analogous
substances—what becomes of such peptones? Are they simply
retained by the endoderm cell for its own nutrition ? or are they
passed by that cell away from its surface to subjacent cells,
which thus are nourished by a process of diffusion? or, again,
are the products of digestion returned by the endoderm cell to
the alimentary tract, and carried thence by its ramifications,
as a nutrient fluid, into various regions of the body ?
5. Are there any special kinds of food particles which are
ingested in the solid form by certain endoderm cells, whilst other
food materials are dissolved and distributed by diffusion, in the
same way as are albuminoids and carbo-hydrates, by the ali-
mentary organs of Vertebrata. Is there any ground for sup-
posing that the ingestion of fats in a particulate form by
Vertebrata is a survival of the intracellular digestion now esta-
blished as occurring in Ceelentera and Planarians ?
When we take into consideration the structure of Hydra it
seems possible that the sole nutrition of the ectoderm cells is,
by means of the products of digestion, elaborated by endoderm
122 PROFESSOR E, RAY LLANKESTER,
cells, such products passing through from the endoderm cells to
ectoderm cells by osmosis. And we have definite observations
of Metschnikoff (in the case of Ctenophora) upon the passage of
carmine particles, away from the endoderm cells which took them
up, into mesoderm cells lying beneath them, which favour the
notion of such a passage. It may, however, be noted that the
carmine particles do not appear in this case to have been
digested—that is, chemically changed and dissolved—and hence
the passage of the particles in question is a phenomenon similar,
in essential respects, to the passage of fat particles unchanged
through cells on the surface of the intestinal villi of Vertebrates
to subjacent cells and cell spaces.
On the other hand, when we try to bring the structure of the
Meduse, with their elaborate gastro-vascular canal system, into
relation with the facts of intra-cellular digestion, we find it
impossible to admit that the nutrition of the organism can be
carried on by the mere osmotic passage of nutrient matters from
those cells which are active as intra-cellular digesters to subjacent
cells. Metschnikoff has observed that in many Celentera the
intra-cellularly digestive cells are limited in number and position,
and this fact I can fully establish by my observations on Limno-
codium. Hence the regions in which subjacent cells can be
nourished by superjacent intra-cellularly digestive cells is ex-
ceedingly limited. The products of the digestive activity of the
intra-cellularly digesting endoderm cells are in all probability,
in the Medusee, returned to the alimentary canal, and carried on
by the agency of the gastro-vascular canals into the remoter
parts of the organism.
Bearing in mind these considerations we may proceed to an
examination of the endoderm of the gastric and gastro-vascular
cavities of Limnocodium.
INTRA-CELLULAR DIGESTION IN THE PROXIMAL REGION OF THE
Gastric TUBE OBSERVED DURING LIFE.
The manubrium of Limnocodium is a somewhat quadrangular
tube, which depends during life below the margin of the um-
brella. Its cavity, the stomach, presents a considerable difference
in the structure of its lining cells, the gastric endoderm, in
different regions. Where the four angles of the stomach-tube
are inserted into the umbrella they are slightly produced, and
give rise to the four radiating canals. The enlarged angles of
the stomach are lined by peculiar cells,in which I observed an
intra-cellular digestion to be proceeding during the observation
of living specimens. In Plate VIII, figs. 1 and 2, two drawings
of this intra-cellularly digestive endoderm, taken from living
specimens, are reproduced. The cells are seen to form a widely-
DIGESTION AND ENDODERM OF LIMNOCODIUM. 125
open meshwork, large spaces occurring between neighbouring
cells, the cells being connected by ridges, which traverse the
spaces. The cells themselves appear to be naked, and their
protoplasm is irregularly aggregated so as to form masses with
pseudopodia-like processes, and also clothing the ridges connect-
ing cell with cell. Spherical nuclei (a), with spherical nucleoli,
are placed at intervals in the protoplasm, and have a uniform
appearance and size, which is characteristic of the endodermal
nuclei throughout the gastric and gastro-vascular area. They
measure about ;,'>>th inch in diameter, whilst the spaces in the
meshwork are onan average about z,',,th by >'scth of an inch
in the smallest and largest diameter. In the neighbourhood of
the nuclei are numerous dense-looking masses of an ill-defined
shape, which give to the cell-substance a certain opacity (0).
In fig. 2 there are also seen vacuole-like spaces or clearer
portions of the cell-substance, containing very dark minute
granules.
In both figures there are seen embedded in the protoplasmic
net-work green unicellular organisms.
In fig. 1 a large Huglena-like form (7) is embedded in a
plasmodium formed by the confluence of cell-substance from
some four or five cells. In the upper part of the figure two
Protococci are. seen embedded in pseudopodia-like processes of
the cell network. ‘The one to the left (y) is in a state of dis-
integration, that to the right (z) has not yet been altered
appreciably. .
In fig. 2 the letter 2 points to an ingested organism, which has
been almost entirely broken up and its colouring matter lost ;
y warks a Protococcus reduced to the condition of a few
coloured granules, whilst z is placed near a recently ingested
Protococcus.
I did not observe the movement of the pseudopodia-like
lobes of this protoplasmic network during life, nor the actual
process of the entry of a solid food particle into its substance.
I may mention in this connection that the proximal region of
the stomach in many specimens of Limnocodium was infested by
a remarkable little free smimming, yet tubicolous Rotifer, which
carried its tube about with it as it swam.
This parasite appeared to escape altogether the embraces of the
amceboid endoderm cells, as well as to be unaffected by the
digestive secretions, if any such were present.
STRUCTURE OF THE Gastric ENDODERM OF VARIOUS REGIONS,
AS SEEN ON TREATMENT WITH REAGENTS.
The true structure of the endoderm of the gastric tube becomes
evident when specimens which have been treated with osmic
124 PROFESSOR E. RAY LANKESTER,
acid are stained with picro-carmine and examined under the
highest powers of the microscope by means of teazing and sec-
tions. ‘The meshwork of ameeboid cells in which intra-cellular
digestion takes place is seen to be confined to the four proximal
angles of the gastric tube.
Endoderm of radial canals.—The endoderm suddenly changes
its character at the commencement of the radial canals (see
Plate IX, fig. 8 w), and in these continuations of the gastric
chamber, instead of a network, we find closely-set nuclei, the cell
areas not distinctly marked off from one another and the proto-
plasm free from granulations. ‘These cells as seen in the living
condition are ciliated.
The nuclei are precisely similar in form and size to those of
the gastric tube, and take up the carmine staining in a way
which is characteristic of the endoderm nuclei in general (see
Plate).
Doiodern of the ring-canal.—I have in my former paper on
Limnocodium (this Journal, July, 1880) described and figured
(Plate XXX, fig. 6) the modification of the endoderm cells on
the abumbral wall of the marginal ring-canal. The cells of the
adumbral wall are like those of the ring-canals. The cells of
the abumbral wall are modified by the deposit of block-like
masses of a dense substance within them, which usually obscure
the nuclei. These cells also have a remarkably angular and
irregular form. They form the representative in Limnocodium
of the cartilaginous marginal ring of Trachymeduse, and are
drawn out into lobes which are continuous with the roots of the
tentacles. The endoderm of the gonads (genital pouches) has
a similar structure to that of the abumbral wall of the ring-
canal.
Endoderm of the gonads.—A portion of this part of the endo-
derm is drawn in Plate IX, fig. 9. It quite closely resembles
that of the abumbral wall of the ring-canal. The block-like
deposits within the cells and the dark colour which the whole
layer had assumed under the influence of osmic acid were suffi-
cient to obscure the nuclei, which accordingly are not seen in
the drawing.
Endoderm of the middle third of the gastric tube.—This is
represented in Plate X, figs. 1 and 2. Over a comparatively
small area the cells present a uniform hexagonal pavement when
viewed from their free surface (Plate X, fig. 2). The nuclei
have the same size and character as in the other endoderm cells,
but the cell substance is small in quantity and of a homogeneous
appearance. Here and there in this and in other parts of the
gastric tube, nematocysts are scattered in considerable numbers,
They sometimes are embedded in the endoderm (g g) so as to
—"
DIGESTION AND ENDODERM OF LIMNOCODIUM. 125
present a spherical appearance, and the first explanation of their
appearance here which suggests itself, is that they have been
developed in endoderm cells. But the fact that they are scat-
tered very irregularly and occur in all regions of the gastric tube
sporadically is against this view. Further the absence of any
cells of the endoderm in which stages of the development of
such nematocysts can be made out is also against the view that
they are developed here. Lastly, the facts that they are pre-
cisely similar in appearance and size to the nematocysts of the
tentacles, and that actual bits of ectoderm cells containing three
or four nematocysts side by side may be observed occasionally in
the gastric tube, are in favour of the view that the nematocysts
occurring in the gastric endoderm have been swallowed by the
Medusa with its prey, and have become embedded in the soft
endoderm fortuitously.
This explanation has been offered by Mr. Marcus Hartogg
(see this Journal, 1880) of the similar occurrence of nemato-
cysts in the endoderm cells of Hydra; and for the present case,
as well as that of Hydra, it seems to me to be satisfactory,
though it must be remembered that there is no great improba-
bility connected with the development of nematocysts by endo-
derm cells unless the mesenterial filaments of the Anthozoa can
be shown to have an ectodermal origin.
Above and below the limited region of homogeneous hexagonal
cells the endoderm of the middle third of the gastric tube
exhibits two distinct concomitant modifications (Plate X,
fig. 1).
1. Some of the cells are enlarged and highly granular (4), in
fact have become secretion cells or unicellular glands.
2. The cells are no longer continuous, but here and there the
cell-pavement is deficient, actual gaps of greater or less size (/)
making their appearance between neighbouring cells.
Endoderm of the oral third of the gastric tube.—The endo-
derm of the oral region presents a condition which may be con-
sidered as a development of that last described. In Plate IX,
fig. 3, a plece is represented. All the cells are here either fully
developed as secretion cells (4), large clear bodies about the
rs'soth inch in diameter, or are on their way to this condition
(4). The nuclei have the characteristic form and size (a). The
intercellular spaces (/) are very small and few, whilst surround-
ing the enlarged secretion cells and enclosing the yet young
secretion cells is a sort of laminated matrix (7). This matrix is
to be regarded as an intercellular substance of a horny or gelati-
ginous character. It forms a complete framework to the whole
series of cells, enveloping each of the more fully-grown secretion
cells in a distinct capsule, which is broken through on the free
126 PROFESSOR B, RAY LANKESTER,
surface of the endoderm by circular apertures (Plate IX,
fig. 4) corresponding each to a ripe secretion cell.
The nuclei of the ripe secretion cells are less defined than those
of the younger cells, and IL am inclined to think that they undergo
atrophy, and that the whole secretion cell, when its chemical
metamorphosis is complete, is passed into the gastric cavity. I
am also led to believe that this takes place periodically by the
following observation.
Whilst in some specimens of Limnocodium studied by me the
oral gastric endoderm presented uniformly the appearance repre-
sented in Plate IX, fig. 3, yet in another batch of specimens it
had uniformly a very different appearance, which is drawn in
Plate IX, fig. 6. In this case all the sites which in the former
example were occupied by large-sized secretion cells are empty
(7). The framework (d) remains, and projecting into the empty
spaces, as though destined in their turn to occupy them, are small
secretion cells (0).
I can only interpret these appearances on the supposition that
the large cells are shed when ripe, and that the next generation
grow out into the spaces left, whilst a third generation is de-
veloped from the scattered cells, with at present little protoplasm,
and merely indicated by the nuclei (a). And, further, it seems
that the ripening and shedding of the secretion cells must take
place in the whole of the oral gastric endoderm simultaneously.
It is possible that a periodicity of this kind may be inherent
in the growth and development of these cells. It is also exceed-
ingly likely that the simultaneous clearing off of all the ripe
secretion cells is due to some special act of the Medusa. It is
likely that the act of feeding, of seizing prey, such as Entomo-
straca (on which the Medusa was frequently seen to feed), would
be the determining cause of the clearing out of the secretion
cells.
This hypothesis is borne out by some further facts, to be related
below.
Whether it be accepted or not, it is clear that we have a copious
secretion produced by the oral-gastric endoderm, and it is in the
highest degree probable that this secretion has the action of a
ferment or of a solvent upon the larger food masses taken into
its gastric tube by Limnocodium.
A modification of the endoderm, not unlike this of the oral-
gastric region of Limnocodium, is described by Claus in Cha-
rybdaa marsupialis, that most interesting of all Meduse. In
his admirable memoir on Charybdeea (‘ Arbeiten des Zoolog.
Instituts zu Wien,’ 1878) Claus gives, in his plate iv, figs. 36
and 37, drawings of endoderm from the oral portion of the
gastric tube, closely resembling that figured by me im
DIGESTION AND ENDODERM OF LIMNOCODIUM. 127
Plate IX, fig. 3. Claus distinguishes two kinds of gland
cells, corresponding to what I believe to be young and old
stages of one kind of gland cell. A difference exists in the fact
that in Charybdzea ciliated cells are interspersed among the
gland cells, whilst such do not appear to be present in the same
region in Limnocodium.
Endoderm of the proximal third of the gastric tube.—As we
pass upwards towards the umbrella, along the walls of the gastric
tube, the endoderm cells gradually open out, leaving intercellular
spaces, and where the tube expands slightly in the horizontal
plane the characters exhibited in Plate IX, figs. 1 and 2, are
assumed. ‘This is the region which has already been described
above in the living condition, and in which intra-eellular digestion
takes place.
A comparison of figs. 1 and 2, Plate IX, with figs. 3 and 6
of the same plate, shows that we have in this region the same
elements of form to deal with as in the oral region, but somewhat
differently characterised. There are large inter-cellular spaces
(7), which are marked off by a somewhat fibrillated or laminated
framework (d) ; spherical nuclei, which take the carmine staining,
are scattered irregularly, and have surrounding them a proto-
plasmic cell substance, which is very deficient in some parts,
and is aggregated in other parts; it appears to be continuous
throughout, and is not marked off into separate cells corre-
sponding to the individual nuclei. Two nuclei are often closely
approximated, indicating recent division, but I have not met with
any in process of division. .
Corresponding to the secretion cells of the oral-gastric
endoderm are circular or oblong groups of oval bodies of a
refringent substance (4), which appear to correspond to the
groups of large granules seen in the living specimens. As now
seen (after the action of reagents), these groups appear to be
formed by oval droplets of a homogeneous transparent substance,
which stain of a pale-pink colour with picro-carmine, and are
strongly emarginated by the difference of refractive index
between their substance and that of the material in which they
are deposited. Whilst representing, in position and size, the
secretion cells of the oral-gastric endoderm, these bodies have a
different structure from those cells, and the substance which
stains pink is unlike anything present in that region.
Large vacuole-like spaces also occur (ee), in which a few
dark granules and irregular particles may be observed, whilst
the substance filling the vacuole is transparent, and stains pink
with picre-carmine. It also appears to have been precipitatea
as a homogeneous or excessively finely granular solid by the
action of the reagents.
128 PROFESSOR E. RAY LANKESTER,
The substance filling the vacuoles (e) is apparently identical
with the substance filling the numerous oval spaces of the bodies
(66). At the same time there can be little doubt, from the
comparison of the prepared specimens with the living, that the
vacuoles are food vacuoles, viz. spaces into which solid food
materials have been taken and digested. Accordingly the material
which they contain is an albuminous substance resulting from
the digestion of those food particles.
From these considerations it seems not improbable that the
pink substance of the bodies (4) is also an albuminous substance
resulting from digestive activity.
I submit as suggestions for further examination, when the
histology and physiology of the endodorm is attempted in other
Meduse, that these bodies (0) are either points at which numer-
ous small food particles have been incepted and digested by the
protoplasm, or, what is more probable, that they are portions of
the protoplasm of this remarkable meshwork which are espe-
cially active in “working up” the products of intra-cellular
digestion, and that they periodically discharge the albuminous
product of digestion and elaboration into the gastric chamber,
whence it passes into the radial canals and marginal canal to
nourish the outstanding parts of the organism.
That albuminous substances in a digested state must pass
into these canals, either in this way or as the result of the diges-
tion of a portion of the food by juices secreted into the gastric
cavity, appears obvious when the limited number and area of the
intra-cellularly digestive cells is considered.
Projecting into the spaces (/) of the meshwork are pseudopo-
dia-like processes (c¢ in figs. 1 and 2, Plate 1X); these are not
only given off from the larger masses of cell-substances, but
appear to spread along the fibro-laminar trabecule (@) of the
meshwork, and whilst clothing the trabecule, and often project-
ing from them into the inter-cellular spaces, also keep the
protoplasm of neighbouring masses in continuity.
Just as in the oral-gastric endoderm, two very different con-
ditions of nourishment and activity were observed, so here in the
endoderm of the proximal end of the gastric tube—which I will
call the ingestive endoderm—there were two very different con-
ditions which came under my observation. The two conditions
of the ingestive endoderm were definitely related to the two con-
ditions of the oral endoderm, When the oral endoderm pre-
sented the condition of abundant large secretion cells filling up
the inter-cellular spaces (Plate IX, fig. 3), then the ingestive
endoderm had the appearance just described (Plate IX, figs. 1
and 2). It was active in throwing out pseudopodia into the
large inter-cellular spaces, and was feeding upon the small
DIGESTION AND ENDODERM OF LIMNOCODIUM. 129
particles (such as Protococci and Euglenz) which chance threw
in its way. In fact, whilst the oral endoderm was full and
unshed, the ingestive endoderm at the other end of the gastric
tube was half-starved, with great inter-cellular spaces and eager
pseusopodial processes, making the best of bad times, and taking
up materials previously unprepared.
In those specimens, however, in which the oral endoderm had
shed its secretion cells, and in which I have supposed that an
act of swallowing some large prey had recently taken place—in
these the ingestive endoderm of the proximal end was totally
changed in appearance. It was gorged with finely granular
matter; its inter-cellular spaces had almost entirely disappeared
in consequence of the swelling out of the protoplasm, now
remarkable for its granular structure.
The appearance is represented in Plate XI, fig. 5. The
masses of oval metamorphic products (6 0) are still present, but
the spaces are reduced to a few small chinks (f). The trabe-
cule of the framework are no longer visible, owing to the
swelling of the protoplasm and its granular opaque character ;
they are concealed by the contiguous edges of the enlarged
masses of protoplasm.
I conceive this change to be due to the absorption by the
ingestive cells of a very abundant supply of albuminous matters
obtained by the digestion in the cavity of the gastric tube of a
Daphnia, Cyclops, or some such form. The raw products of
gastric digestion—partly dissolved partly in the form of fine
particles—would, it may be assumed, be taken up by the ameeboid
ingestive cells, just as are the rarer living food-particles in
times of dearth when so copious a feast as that afforded by a
Daphnia is not forthcoming.
As to the return of the ingestive endoderm to its meshwork
state, with pseudopodia ready for the inception of large food-
bodies, | have no observations to offer, and I will not speculate
further upon the possible activity of the ingestive endoderm in
elaborating the food matters taken in by it.
It is a matter for regret that the fresh-water Medusa died
down in the lily-house tank a few weeks after its discovery, so
that I have not been able to follow up experimentally some of
the suggestions which the study of the endoderm has afforded
me. It would be an easy matter with Limnocodium and, indeed,
with other small Medusz, to determine experimentally the con-
dition of the endoderm cells of different regions of the gastric
tube before, during, and after the introduction into that tube
of an Entomostracous Crustacean.
The observations and interpretations which I have put forward
in the preceding pages cannot be regarded as more than an
VOL. XXI.—NEW SER. I
150 PROFESSOR E. RAY LANKESTER.
early contribution to the subject of intra-cellular digestion and
the comparative physiology of digestion in general, which I do
not doubt is about to be investigated with new vigour and
interest, in consequence of Metschnikoff’s researches.
SuMMARY.
1. The cells of the endoderm of the gastric tube and gastro-
vascular canals differ very considerably in form and in the
chemical metamorphosis of its substance in different regions.
2. The nuclei are alike in all as to size and form, excepting
in the cells of the abumbral wall of the marginal canal and the
similar cells of the endoderm of the genital pouches.
3. These latter are angular, close-set cells, with dense block-
like deposits in their protoplasm concealing the nucleus.
4, The cells of the radial canals are close set and ciliate with
sparse, hyaline protoplasm.
5. The endoderm of the gastric tube is divisible into three
regions: a, the oral, J, the mid-gastric and ¢, the ingestive or
proximal.
6. Only the cells of the proximal region exhibit intra-cellular
digestion.
7. The cells of the oral region produce a secretion by their
development as secretion cells (goblet cells of Claus).
8. The cells of the mid-region are inactive.
9. The cells of the proximal region appear, under certain
circumstances, as an open meshwork giving off amceboid pro-
cesses, by means of which they take in solid food particles.
10. Under the same circumstances the secretion-cells of
the oral region are richly developed and in place.
11. Under other circumstances the cells of the oral region
appear to have been, to a large extent, shed, leaving inter-cel-
lular spaces.
12. When this is the case, the secretion-cells of the proximal
are swollen and granular, and the inter-cellular spaces of the
meshwork obliterated.
13. It is inferred that the latter circumstances are the result
of the taking into the gastric tube of relatively large prey;
whilst the former condition is one of comparative fasting, in
which such small food bodies as may be ingested by the endo-
derm of the proximal region are proportionately valuable to the
organism.
ADDENDUM ON THE ENDODERM OF THE TENTACLES.
In Plate X, fig. 3, a surface view is given of one of the
smallest sized tentacles, for the purpose of showing the mode in
which the thread-cells are clustered in groups upon its surface.
DIGESTION AND ENDODERM OF LIMNOCODIUM, , roe
These groups appear to have a spiral arrangement, more or less
definitely expressed. In fig. 6 two thread-cells are represented
with ejected filament, showing the series of six small barbs at its
base. In fig. 4 an optical median longitudinal section of the
tentacle is drawn, in order to show definitely the character and
arrangement of the endoderm cells. The specimen from which
the drawing was taken had been treated with osmic acid and
picro-carmine. An actual transverse section of a similar ten-
tacle is shown in fig. 5. The endoderm cells consist of a dense,
highly-refringent substance, which is somewhat wrinkled by the
action of the reagent. The nuclei are a little smaller than those
of the gastric endoderm. In some cases a small amount of
granular cell substance may be seen radiating from the nucleus,
but the whole cell body otherwise has been metamorphosed into
a homogeneous cartilaginoid substance. ‘There is no continuous
lumen, although the cells are disposed in a single series around
the axis of the tentacle, and leave, on shrinking, a small space
where their adaxial surfaces should come into contact. This
potential lumen appears not to be continuous, even in the speci-
mens treated by reagents, and in living specimens it has no
existence.
A structureless lamella (Stutz-lamella) (¢) adheres closely to
the endoderm cells. Subjacent to the ectoderm cells are the
very fine transversely-striped muscular processes (d), which are
developed on their inner faces, not only here but in the case of
the subumbrellar ectoderm and of the ectoderm of the adum-
brellar surface of the velum.
132 MRS, ERNEST HART,
On the Micromerric Numpration of the Btoop-cor-
PUSCLES and the Estimation of their HmMOGLOBIN.
By Mrs. Ernest Hart.
THE micrometric numeration of the blood-corpuscles and
the estimation of hemoglobin are operations which, though
of comparatively recent introduction, have rapidly passed
out of the sphere of laboratory experiment into practical
use as exact methods of physiological and clinical investiga-
tion. Those who have worked at this subject cannot, how-
ever, have proceeded far without discovering that the
methods and instruments hitherto in use are inconveniently
imperfect and vitiated by numerous sources of error. Some
recent improvements by M. Malassez, assistant in the La-
boratory of Histology in the Collége de France, appear to
me to have done much to remove these disadvantages.
Before proceeding, however, to describe the new Corpuscle-
Counter which M. Malassez has just introduced, it may be
well to say a few words on the methods and instruments
usually employed for the numeration of the corpuscles. The
three which have been hitherto in general use are those
known as the instruments of Malassez, Hayem, and Gowers.
In the method first invented by Malassez (the Compte- Globules
Capillaire) 100 parts of a 5 per cent. solution of sulphate of
soda are mixed in a special instrument called the Melangeur
Potain (Fig. 1) with one part of blood. This solution is then
drawn into an extremely fine capillary tube. The calibre
of this tube is known ; hence the volume of the fluid which
the tube contains in a given length, say in 500, 400, or 300
micro-millimeters is alsoknown.! This volume is some frac-
tion of acubic millimeter. It follows that the volume multi-
plied by the denominator of that fraction will equal a cubic
millimeter. The multiplier is written on a glass plate, on
which the capillary tube is mounted. Before using the instru-
ment the eye-piece of the microscope must be exchanged for
an eye-piece containing a micrometer divided into a number
of square millimeters. Then by means of a stage micro-
meter, the microscope must be graduated, so that ten of the
square millimeters of the eye-piece correspond exactly to
the arbitrary length (500u, 400u, or 300m) fixed upon. A
mark being then put on the tube of the microscope, this
magnifying power—the lens being always the same—can
be easily found again. The process and calculation are then
1 This unit, the thousandth of a millimeter, is expressed by the Greek yu.
MICROMETRIC NUMERATION OF THE BLOOD-CORPUSCLES. 133
very simple. The solution of blood, after being well shaken
in the Mixer, is drawn up into the tube by capillary attrac-
tion, and the number of corpuscles contained in the given
length of the tube is counted. This is
rendered extremely easy by the aid of the
small squares of the ocular micrometer.
The number obtained is multiplied by
the denominator written, as already men-
tioned, on the glass plate, and the pro-
duct multiplied by 100 or 200, according
to the strength of the solution used, gives
the number of the corpuscles per cubic
millimeter. Thus, supposing that, in a
length of 500u, the volume =~, of a
cubic millimeter, and that a 1 per cent.
solution occupying this space contains
300 corpuscles, then
300 x 150 x 100 = 4,500,000
the number of corpuscles per cubic mil-
limeter of blood. The calculation, how-
ever, is not so simple as this in prac-
tice, since the multiplier, of course, will
seldom be a round number.
M. Ranvier, in his ‘ Traité Technique
d’Histologie,’ says that this method, con-
sidering the short time it takes, gives, of
all those hitherto known the best results.
It is certainly very accurate, but it has
two great disadvantages. In the first
place, owing to the necessity of under-
taking the somewhat difficult task of gra-
duating the microscope, the same Compte-
Globules must always be used with the
same microscope and the same lens ; hence
its use clinically is obviously very much
curtailed. Secondly, the extreme deli-
cacy of the instrument is a serious draw-
back. Though a person with ordinary
manipulative skill may learn to use this
instrument, it requires more than ordinary
WiGeae
care to keep the minute capillary tube absolutely clean
and this is positively necessary, since a minute particle of
dirt, or a few dried corpuscles left in the tube, will vitiate
the accuracy of the results. My own experience is that,
though I am able to make correct observations with this
134: MRS. ERNEST HART.
instrument in the pure air of Paris, I am unable in
London, where nothing is clean, not even distilled water,
to keep the tube quite free from dirt.
Hayem’s method differs altogether from that of Malassez.
The unit is arrived at by means of a cell + mm. deep, of
which an area of 3 of a square mm. is marked off. This
gives us, therefore, 1 x 55 = +4, of a mm’. The area of
=!5 square mm. (which is, of course, =; of 1,000,000 square 1)
is obtained by using an ocular micrometer, on which is drawn
an oblong, 5 mm. long by 4 mm. wide, and divided into 20
squares. By means of a stage micrometer the microscope
is graduated so that the 5 mm. exactly correspond to an ob-
jective length of 250u. The mixture of blood and the pre-
serving fluid is made at a strength of 8 per 1000. The
method of mixing is that invented by Vierordt. A pipette,
holding 8 cubic mm., is used to measure the blood; another,
of acalibre of 992 cubic mm., to measure the preserving
solution. The two fluids are mixed in an open glass vessel
by means of a glass rod. The same rod is also used to
deposit the drop on the slide. The cover-glass is kept i
situ by the capillary attraction existing between two moist
glass surfaces, a drop of water or saliva being placed at the
edge of the cover-glass, and allowed to run underit. The
chief objections to this instrument are the uncertain depth
of the cell, the clumsy method of mixing, the possible ele-
vation of the cover-glass by allowing too much water to run
under, it and also the same objection made to Malassez’s capil-
lary Compte-Gilobules just considered, namely, that, owing
to the necessity of graduating the microscope, it is of limited
use as a clinical instrument.
In Gowers’ Hemacytometer,! which is a modification of
Hayem’s, a very decided improvement is made. In the
depth of the cell and in the old-fashioned mode of mixing,
it is identical with that of Hayem; the solution of blood
used being, however, at 5 per 1000 instead of at 8 per 1000.
The improvement consists in measuring the area and drawing
the squares in which the corpuscles are to be counted upon
the floor of the cell itself. Squares, with sides , of a mm.
long, are drawn on the floor of the cell. The area of each,
therefore, is +4, of asq. mm. The cell having a depth of
4+ mm., and any 10 squares an area of +; of a sq. mm., the
cubic contents of any ten squares taken within the cell
will be—
1 “On the Numeration of the Blood-corpuscles,” by Dr. Gowers,
‘ Lancet,’ Dec., 1877.
MICROMETRIC NUMERATION OF THE BLOOD-CORPUSCLES, 135
ty X + = xy mm,
The number of corpuscles observed in ten squares, there-
fore, multiplied by fifty will give the number in a cubic
millimeter of the solution ; and that multiplied by °° will
give the result for a cubic millimeter of blood.
For example, if the number of red corpuscles counted on
ten squares is 500, the calculation is simply
1000
500 x 50 x reins 500 x 10,000 = 5,000,000 per mm.?,
or, in other words, there is nothing to be done except to
add 0000 to the number found by counting. No gradua-
tion of the microscope is required, so that the instrument
can be used anywhere and with any lens. This renders it
more convenient as a clinical instrument, and it is therefore
that which is in general use in the English hospitals. It
gives approximately accurate clinical results. I must, how-
ever, point out that it is liable to four serious sources of
error, which destroy the value of observations made with it
from an absolute and scientific point of view. These sources
of error are—the uncertain depth of the cell; the inequality
of the surface of the cover-glass; the method of placing the
cover-glass on the drop; and the means used to make the
mixture and to place the drop in the cell. Since a paper
by two American physicians was published,! showing how
careful observations may be vitiated by the variation in the
depth of the cell in different instruments, the error in the
depth has been written on the slide. In the Hemacytometer
which I habitually use the cell has a depth of 190n, instead
of 200u. This error necessitates a troublesome correction
in each calculation. The correction is made by multiplying
the number of corpuscles obtained by 20 and dividing by
19; for let @ equal the number of corpuscles in a mm.?
multiplied by the actual depth of the cell,
190u:a:: 200u: z.
This method of correction which is that recommended is,
however, irksome when a great number of observations have
to be made. I wish now to suggest that it may be alto-
gether avoided by directing the instrument maker to gra-
duate the pipette or mixer, whichever may be used, not, as
at present, on the assumption that the depth of the cell
accurately measures 200, and therefore that a solution of 5
1 “ Blood-Cell Counting: a Series of Observations with the Hématimétre
of M.M. Hayem and Nachet, and the Hemacytometer of Dr, Gowers.”
By Drs. Henry and Naucrede.—‘ Boston Med. and Surg. Journ.,’ April,
1879.
136 MRS, ERNEST HART.
per 1000 should be used to ensure correct results, but so to
graduate it as to make a solution of such a strength that,
having previously ascertained the actual depth of the cell an
area of ;!; mm.? multiplied by this depth shall give 1, mm.°
In this way the necessity for arithmetical correction of each
observation is avoided, the special adjustment of the pipette
affording a correction which applies to all observations made
with the instrument. Thus, taking my own Hemacytometer
as an example, if, instead of using a 5 per 1000 solution, a
5 per 950 solution were used, z.e. 5 parts of blood to 945
of the diluting fluid, the result would be absolutely the same
as if the depth of the cell were correct, or as if the error were
corrected by calculation. Thus supposing 500 corpuscles to
be contained in ten of the squares,
1000 950
500 x 10 x 190° Xe he 5,000,000.
This device will work equally well whatever the error in
the cell may be, if the following rule be adhered to :—
Multiply the actual number of w in the depth of the cell
by 5 and take the product as the number of parts of the
solution of blood and diluting fluid to be used, the number
of the parts of blood remaining constant at five-—
190u x 5=950
or, still more generally, the number of parts of blood being
fixed, and the actual depth of the cell in » being known,
the product of these two numbers, minus the number of
the parts of blood, will give the necessary number of parts
of diluting fluid required.
With the pipette or mixer graduated according to these
rules, it will only be necessary to add 0000 to the number
of corpuscles counted in ten squares.
I commend this suggestion to the notice of all who are
using Gowers’ instrument, as its adoption will greatly
facilitate the attainment of correct results.
Secondly, as to the error caused by the inequality of the
surface of the cover-glass. Any ordinary cover-glass is used
to flatten the drop to an uniform height. Now, as every
histologist knows, cover-glasses are rarely of an uniform
flatness; they are generally either slightly convex or con-
cave, hence the layer of fluid is likely to be thicker in some
places than in others, and consequently a count made in
one part of the cell may give very different results from
one made in another. To remedy this defect in my instru-
ment, I have had ground a perfectly flat cover-glass.
Thirdly, the mode of placing the cover-glass on the cell
MICROMETRIC NUMERATION OF THE BLOOD-CORPUSCLES, 137
is faulty; whether it is dropped on horizontally or laid on
gently at an inclined plane, the uniform diffusion of the
corpuscles through the fluid is disturbed.
Fourthly,in the method of mixing and placing the drop on
the cell, errors are caused by the white corpuscles adhering
to the sides of the vessels used for mixing, and by evapo-
ration from the little open cup in which the solution is
kept. Further, in placing the drop on the slide, unless the
manceuvre is very quickly executed, the red corpuscles
gravitate tothe bottom of the drop, and are thus deposited
and form a thicker collection in the centre of the drop than
at the periphery. The white corpuscles also, by adhering
to the glass rod, introduce a source of error in estimating
the right proportion between white and red corpuscles.
It is, I think, to be regretted that, in introducing this really
useful clinical instrument, Dr. Gowers should have adopted
the old, clumsy, and discarded method of making the solu-
tion, instead of using Potain’s Mixer, the use and value of
which were already known. By this mixer a solution of
blood at 100, 200, 300, 400, or 500, as desired, is made in
a closed vessel, evaporation thus being prevented ; the drop
is deposited on the slide whilst the corpuscles are in rapid mo-
tion and before they have had time to gravitate to the bottom
of the drop. For the last eighteen months I have, when
using Gowers’ Hemacytometer, substituted Potain’s Mixer
in the place of the apparatus provided, and with the result
of obtaining much more uniform counts in different parts of
the cell, whereas previously the want of uniformity was often
very marked.
By the means I have indicated, namely, by correcting the
error in the depth of the cell, by substituting a perfectly flat
cover-glass for one that may or may not be flat, and by using
Potain’s Mixer for making the solution, a useful and nearly
accurate clinical instrument can be made of Gowers’ Hema-
cytometer. As it isat present arranged, the results obtained
by it are often misleading, unless the mean of a great
number of counts be taken. Single observations are likely
to lead to the most fallacious conclusions, and are not at
all trustworthy, whether for scientific or clinical data.
In Malassez’s new Compte-Globules he has adopted
the great improvement introduced by Gowers, of drawing
the squares on the surface of the slide. He has more-
over succeeded, by many ingenious contrivances in care-
fully avoiding all the sources of error in Hayem’s and Gowers’
instruments above enumerated, to several of which I had
occasion to call his attention. This new MICROMETRIC GRA-
138 MRS. ERNEST HART,
DUATED CORPUSCLE-COUNTER with WET CHAMBER (Compte-
Globules a chamhre humide graduée micrometrique!) consists
of a thick nickel slide, in the centre of which is a circular
groove enclosing a glass cylinder about a centimeter in dia-
meter. Outside this groove are three pointed metal screws,
equidistant from each other. The elevation of these points
above the surface of the metal slide is exactly} mm. In the
centre of the glass surface, limited by the groove, are
drawn the squares, in which the corpuscles are counted.
These havea side of 3'5 mm., and they are arranged in groups
of 20, each group having a length of 3;=! mm., and a width
of »4 =+mm., and an area, therefore, of }x 1=y5 square
Fie. 2.
mm. Each group of 20 squares is separated from ad-
joining groups by a double line (Fig. 2). The peripheral
1 “Sur les Perfectionnements les plus récents apportés aux Méthodes
et aux Appareils de Numération des Globules Sanguins, et sur un nouveau
Compte-Globules,” par L. Malassez, ‘ Arch. de Phy.’
MICROMETRIC NUMERATION OF THE BLOOD-CORPUSCLES. 139
parts of the ruled space are simply divided into rectangles,
z mm. long and + mm. wide. The cover-glass, which is
ground accurately flat, is attached, by moistening the edges
slightly with saliva, to a frame fixed to the sides of the slide.
By an ingenious and delicate rack movement of this frame the
cover glass is lowered without delay, and in a horizontal posi-
tion down upon the drop. ‘The slide carrying the frame is
represented in Fig. 3,
Fie. 3.
To make a numeration, the solution is made in Potain’s
Mixer at the strength of 1 per 100, 200, 300, 400, or 500, as
desired ; and, whilst being rapidly agitated, a drop is placed
in the centre of the ruled space, and the cover-glass, having
been previously attached to the frame, is lowered and
clipped, so as to rest firmly on the points of the screws. To
prevent evaporation, if desired to keep the preparation any
length of time, a drop of water should be placed at the edge
of the cover-glass, and allowed to run under and fill the
vacant space between its edge and the groove. The red
corpuscles that are lying within a group of 20 squares
are then counted. These 20 squares, it will be remembered,
have an area of z5 mm.*, and the depth of the fluid
being + mm., the quantity of the solution under review will
be g5 x 4=745 of amm.® The number of corpuscles seen,
therefore, has to be multiplied by 100, and then again
by the number representing the strength of the solution, and
the product will be as before the number of corpuscles in a
cubic millimeter of blood.
Thus, for example, let the solution be 1 per 200, and let
250 corpuscles be found on an area of 45 mm.?; then—
250 x 100 x 200 = 5,000,000.
Thus, to the number of corpuscles counted, if the solution
140 MRS. ERNEST HART,
be 1 per cent., it is only necessary to add 9000, but if
the strength of the solution be less it is necessary to multiply
the number of corpuscles by the figure representing the
dilution before adding 0000. To correctly estimate
the number of white corpuscles per cubic millimeter a
much larger area must be taken, and for this purpose the
rectangles of 5 square mm. have been drawn on the slide.
The number of white corpuscles found in ten of these large
rectangles must be counted. If in a 1 per cent. solution the
number of white corpuscles in ten of these large rectangles
is found to be thirty, then we know, as above shown, that
the volume of the solution counted is—
10 x 3, x torl0 x z45 = Hy mm?
The number counted, therefore, multiplied by 10 and then
by 100, will give at once the number of white corpuscles in
a cubic mm. of blood; or, in other words, it is only neces-
sary, for a one per cent. solution, to count and add 000.
For example:
30 x 10 x 100 = 30,000.
This method of estimating the number of white corpucles
will be felt by every worker at this subject to be a great
gain, for on this point none of the previous instruments
gave any but the roughest approximate results, likely to
give rise to the most delusive conclusions. ‘To sum up, the
advantages of this new Compte-Globules over that first intro-
duced by M. Malassez are that it can be used clinically
with any microscope, that no particular skill is required to
use it, and only ordinary care to keep it clean and in order.
Over other clinical Corpuscle-Counters it possesses the
merits—of making the layer of fluid accurately + mm. in
depth, so that there are no corrections to make; of having
the squares ruled to the smallest size yet found possible, so
that the numeration is exceedingly easy and not fatiguing
to the eyesight; of making an exact computation of the
number of white corpuscles per cubic mm.; and, lastly, by
means of the rack movement of the carrier of the cover-
glass, and by the use of the Melangeur Potain, of preserving
the homogeneity of the drop when placed on the slide and
flattened to the depth of + mm.
The counting of blood-corpuscles is now so common and
frequent an operation in clinical medicine, and its value in
assisting diagnosis and treatment is so well recognised, that
I feel sure that insistence on the minute details and scrupu-
MICROMETRIC NUMERATION OF THE BLOOD-CORPUSCLES. 14]
lous care necessary to ensure correct and reliable results will
not be thought trivial.
Corpuscle counting is, however, only one stage in the
optical investigation into the state of the blood. ‘To arrive
at an opinion on which diagnosis and treatment should be
based, it is necessary to estimate the amount of hemoglobin
as well. In an elaborate paper! of Malassez (of which I
published an abstract in the ‘London Medical Record’ of
1879), all the various methods employed for estimating
hemoglobin are described at length. In nearly all of these
an arbitrary standard of colour is taken as normal, and the
blood to be examined is compared with it. In Malassez’s
Hemochromometer there is no arbitrary standard; each
degree of the coloured standard solution to which the blood
is compared corresponds to a blood containing a certain
estimated amount of hemoglobin per cubic mm., and having
the power of absorbing a certain known amount of oxygen.
These figures have all been ascertained by a prolonged
series of experiments; here therefore, there is no guessing
that the amount of hemoglobin may be above or below the
normal, for we are able to ascertain the actual amount of
hemoglobin in a cubic mm. of. blood, and also the respira-
tory power of the same unit. But M. Malassez points out
that it is not only necessary to ascertain the amount of
hemoglobin per cubic mm., but that we should learn in
what state of division it exists, namely, what is the amount
contained in each corpuscle. Welcker considers that there
is always a constant relation physiologically between the
richness of the blood in corpuscles and in hemoglobin ;
Hayem and Johann Duncan have, however, discovered that,
pathologically, particularly in anemia and chlorosis, the
relations are disturbed, the number of corpuscles often rest-
ing normal, the hemoglobin being less than normal. The
way of arriving at the amount of hemoglobin per cor-
puscle is, by M. Malassez’s method, extremely simple. The
number of corpuscles in a cubic mm. of blood is first
counted, and by the hzemochromometer the amount of
hemoglobin per cubic mm. is estimated. The latter figure
divided by the former gives the amount of hemoglobin per
corpuscle. ‘[Thus, a blood containing 5,000,000 corpuscles
per cubic mm., and 0°125 mlgr. of hemoglobin per mm.
gives 5050000 = ‘000,000,025 mlgr., % €. a.50 000 of a
000,000 Of a gramme, or, as it is commonly written,
1 «Sur les diverses Méthodes de Dosage de L’Hémoglobine et sur un
nouveau Colorimétre,” par L. Malassez, ‘ Arch. de Phy.,’ 1877.
142 MRS. ERNEST HART.
25 mugr. The result in terms of pu gr., however, may be
found in a moment by simply dividing 125 by 5 = 26, and
disregarding all ciphers.
In an extremely interesting research,’ M. Malassez found
that, pathologically, the estimation of the hemoglobin per
corpuscle gave very significant indications. In a case,
which he quotes, of chlorosis which improved under treat-
ment, the actual number of corpuscles per cubic mm.
diminished, the amonnt of hemoglobin per corpuscle, almost
doubling, however, in the same time; mere corpuscle
counting here would have given an erroneous inference. In
a series of experiments on fowls kept first at liberty in the
open air, and then in unhealthy conditions in a courtyard,
it was found that though the corpuscles did not notably
diminish in number, the hemoglobin per corpuscle fell
from 48 yu gr. to 33 uu gr. On examining a great number of
animals he found that the lower in the scale one descends
the larger the amount of hemoglobin per corpuscle, so that
it might be too hastily assumed that the blood of the lower
animals was richer in hemoglobin than that of the higher.
At one end of the scale stands man with a mean normal of
30 wu gr., and at the other the Proteus with 1066°6 yy gr.
But the corpuscle of the Proteus is 127 times the volume
of that of the human subject. The true ratio between
them can only be ascertained by knowing the amount of
hemoglobin contained in an unit of corpuscular substance.
The unit taken is u®. To obtain this, the volume of
the corpuscle must be known. Welcker, by an elaborate
process, ascertained the mean volume of the corpuscles of
a few animals as standards of comparison. These measure-
ments being accepted as accurate, the amount of hemoglobin
per corpuscle is divided by the mean volume of the corpuscles,
and the product is the amount of hemoglobin per yp? of
corpuscular substance.
From the following table it will be seen that though the
quantity of hemoglobin per corpuscle may increase from the
higher to the lower animals, the true ratio of comparison is
the unit of corpuscular richness in hemoglobin, and that
this, on the contrary, rises in passing from the lower to the
higher animals :
Welcker’s ingenious method of ascertaining the value of
1 “Sur la Richesse en Hémoglobine des Globules rouges du Sang,” par
L. Malassez, ‘ Arch. de Phy.’
MICROMETRIC NUMERATION OF THE BLOOD-CoRPUSCLES, 143
. tity of heemo-
h sasakee us ae Volume of the bare es be ee
Thorpascle corpuscle, Bd
pee gr. pw cube. My gr.
Man . . : ‘ 30 72 04166
Pigeon . ; 3 : 52 125 0°4160
Lizard . ; ‘ ; 70 201 0°3483
Russian frog. : ; 216 629 03432
Proteus : é : 1066 9200 01159
the volume of the corpuscles in ° is, however, quite out of
the question in clinical work, and as no simpler method has
at present been devised, we must it appears to me, be at
present content to ascertain the mean area of the corpus-
cles in w”, and to take as our unit of corpuscular substance py?
multiplied by the unknown thickness of the corpuscle, on the
assumption that this is uniform throughout, and always the
same. Actually we know this not to be the case, as normal
corpuscles are biconcave and not flat, and in pathological
conditions they vary in form, and possibly in thickness.
However, let the constant representing the supposed thick-
ness (or more accurately the factor by which we should
multiply the diameter to obtain the volume) be called r.
Our arbitrary unit of corpuscular substance will, therefore,
be ru. The results in the way of comparison will only be
liable to error in so far as the corpuscles vary in thickness.
As, however, this variation is immeasurable by our present
instruments, it may be taken that the unit 72 will give for
all practical purposes a sufficient approximation to the
truth.
To obtain the mean area of the corpuscles in any given
specimen of human blood, the mean diameter of the cor-
puscles must first be ascertained. A simple method of
obtaining this is to graduate the microscope so that an image
thrown by the camera lucida at a certain flxed distance
magnifies exactly 1000 diameters. The corpuscles having
been rapidly fixed and dried by exposing them to the action
of heat, or better still, to the vapour of osmic acid, their image
is thrown by the camera lucida on to white paper, care being
taken to correct the errors of refraction.! The outlines of
the corpuscles are then traced in pencil, and their diameters
1 “Note sur la Mesure des Grossissements Microscopiques,’ par LL
Malassez. ‘Correction des Déformations produites par les Chambres
Claires de Milne-Edwards et de Nachet,’ par L. Malassez.
144 MRS, ERNEST HART.
measured by a millimeter rule. The resulting numbers
give the diameters of the corpuscles in micro-millimeters.
Of course the mean of a great number of measurements
must be taken. I generally take the mean of fifty measure-
ments. The area in yp” is obtained by the well known
formula of mr’.
To take an example:
Let 7°60 = the diameter of a normal corpuscle ;
and 3°8u = the radius: then
mr? = 7. 14:44u? = 45°36p?.
45. 36? is therefore the area of a normal human corpuscle.
To obtain the unit of corpuscular richness, 7. e. the amount
of hemoglobin in a volume of ry”, the amount of hemo-
globin per corpuscle must be divided by the area.
In the following table, which I have prepared, these cal-
culations, and others to which reference has been made
above, have been worked out. The number of corpuscles in
a cubic millimeter is taken as invariable in the examples of
normal and anemic blood (this is not infrequently the case) ;
all the other figures vary, however, from the normal in dif-
ferent degrees, the unit of corpuscular richness being finally
the only figure that gives the exact ratio between the normal
and pathological states.
ee e. Ae (~h 2 ad
oO og o =
= A oie ie ae Bs
ae a2 a : ioe
oe ~ I © Sp = Cy ue
= = o = i = oSs
os oj ag of a ° £22
no BS 2 ns o mn s 0°
Bn 3 ° 23 3 ed Pr. |
es | s3|s2| BS |o| & |S58
On 2 2s ou ° ° S52
Ss Ou om oso H =) ee
g aS — by as Ss
Se on 50 ealss 3 oH oCn
od I S Cs Ss °o Ba
x S os
S = 8 én s 2 & =
Z es ss ZH ra) 4 |
Wh, er. Z
ar. | wy. gr Me M2 | up gr
The corpuscles in a nor-
mal state of health . |4,500,000) 0°134, 29°77/33,580,000) 7°60) 45:36 0°66
Slight anemia, with di-
minution of the size
of the corpuscle - 4,500,000 0°082 18°66 54,878,048 6°50) 33-18 0-56
Marked anemia, with
increase of the size of
the corpuscle . - |4,500,000 0°062 13°77'72,580,645' 8-20 52-81 0°26
Pathologically these exact or minute analyses are most
interesting, though their outcome clinically and therapeuti-
MICROMETRIC NUMERATION OF THE BLOOD-CORPUSCLES, 145
cally is yet obscure. But we may hope that a minute
study of the state of the blood in the cachexia of cancer and
syphilis, in pernicious and simple anemia, in chlorosis and
leucocythemia and in other wasting diseases, may lead to
an exact knowledge of the pathological changes, revealing
the causes at work and that this knowledge may form a
rational basis of treatment.
VOL, XXI,——-NBW SER, K
146 W. B. SCOTT,
Pretiminary Account of the Devetorment of the Lampreys,
By W. B. Scorr, M.A., Assistant in Paleontology,
Princeton, New Jersey.
For nearly a year (1879-80) I was occupied in the laboratory
of Professor Gegenbaur in working out the development of the
Lampreys, the results of which investigations will appear shortly
in a more extendedform. It seemed, however, desirable to give
a preliminary account of the results which have been obtained,
in order, as far as possible, to direct the attention of mor-
phologists to the general character of the development of this
important and little understood group of Vertebrates. Professor
Gegenbaur very kindly placed at my disposal the splendid mate-
rial which was so laboriously and skilfully collected and prepared
by the late Dr. Calberla. ‘This consists of an immense series of
preserved embryos and larve, and of many thousand prepared
sections ; and, in addition to these, I have further obtained a
fine series of larvee, for which I am indebted to the friendly offices
of Professor Wiedershein.
Since the publication of my little article in the ‘ Zoologischer
Anzeiger,’ 1880, No. 63, I have obtained an article by Pro-
fessors Kupffer and Benecke,! which has made it necessary to
alter slightly, though not essentialiy, the statement concerning the
maturation of the ovum contained in my paper. According to
Calberla? the conversion of the germinal vesicle into the female
pro-nucleus takes place simultaneously with the metamorphosis
of the larva into the sexual animal. I was led to doubt this
statement for many reasons, and believed that the germinal vesicle
persisted unchanged until nearly the time of laying. This result
is fully confirmed and extended by those of Kupffer and Benecke.
According to these observers there are two polar bodies formed,
one before and one after impregnation. ‘Ibe one which I men-
tioned as being present in the ovum already segmented into four
corresponds to the latter of these bodies. The first of them 1
did not find, as no fresh material of the proper stage was ac-
cessible to me. According to Kupffer and Benecke this first
polar body is a nucleus-like body surrounded by a membrane,
and embedded in granular protoplasm; it is nearly always ec-
centric in position. The authors just mentioned consider it
highly probable that this body is a derivation of the germinal
' C. Kupffer and B. Benecke, ‘ Der Vorgang der Befruchtung am Hi der
Neunaugin,’ Konigsberg, 1878.
2 HK. Calberla, ‘Der Befruchtungsvorgang beim Hi von Petromyzon
Planeri. Zeitschr. fiir wissensch, Zoologie,’ B, xxx.
PRELIMINARY ACCOUNT OF DEVELOPMENT OF LAMPREYS, 147
vesicle. In short, the maturation of the egg, it seems, offers no
such great peculiarities as Calberla supposed.
Segmentation.—According to my results this process takes
place as Max Schultze! has described it, 7. e. as in the case of
the frog, or rather that of the newt, and not, as Calberla supposed,
in such a way that epiblast and hypoblast are distinguished by the
first division. At the end of segmentation the ovum is very
similar to that of the triton, or sturgeon, of a correspond-
ing stage. There are two kinds of blastomeres, the larger form
the lower half of the egg, the smaller ones the upper half. The
quantity of food-yolk is less than in the eggs just mentioned ;
the segmentation cavity is extraordinarily large, and lies almost
entirely in the upper half of the egg; its cover is made up of
several layers of cells, of which only the exterior will develop
into epiblast. The presence of cells in the roof of the segmenta-
tion cavity, which will eventually belong to hypoblast, occurs
otherwise only in such eggs as have a very large quantity of food-
yolk, e.g. that of Accwpenser.? In general, epiblast and hypo-
blast are roughly distinct at the end of segmentation, but the
strict differentiation, as well as the foundation of the mesoblast,
is produced by the well-known process of invagination. This
is preceded by the thinning out of the roof of the segmentation
cavity, which now consists, for the greater part of its extent, of
a single layer of cells. The invagination is precisely similar to
that of the newt.? By this means are formed in the median dorsal
line two layers of cells, the epi- and hypo-blast, whilst on the
sides we find these two and a third, the mesoblast. In the head
and anterior part of the body the germinal layers are formed only
in this way, while in the greater part of the body the ventral
part of the mesoblast, and by far the greater portion of the
hypoblast, arise by differentiation of the yolk-cells.
This description of the formation of the germinal layers is
very different to that which Calberla* gives. The discussion of
his views would, however, lead us too far, and so it must be
deferred.
I can completely confirm Calberla’s results as to the formation
of the notochord. It is formed from the invaginated hypoblast
alone, but when it becomes detached from this layer it grows
considerably further forward in the head than the hypoblast of
the alimentary canal extends.
1M. Schultze, ‘Die Entwicklung von Petromyzon Planeri,’ Haarlem, 1856.
2 Salensky, ‘Development of the Sturgeon’ (Russian), Part 1, Kasan, 1879.
3 Scott and Osborn, “On Some Points in the Early Development of the
Newt,” this Journal, 1879.
4 Calberla, “Zur Entwicklung des Medullarohres und der Chorda dor-
salis, ete.,”” ‘Morph. Jahrbuch,’ Bd. iu.
148 WwW. B. SCOTT.
* The alimentary cavity (Urdarmhdhle) is formed by invagina-
tion. In the head region this cavity becomes the lumen of ‘the
permanent alimentary canal, but in the body there arises a new
and much larger lumen. ‘The blastopore is enclosed by the
medullary folds, and a neuro-enteric canal is thus formed. As
Professor Benecke! has already discovered, the anus is a new
formation.
The visceral clefts arise as diverticula of the hypoblast
of the throat towards the external skin, which is resorbed at
these points. Ata much later period a shallow sinking of the
epiblast is formed into which all the gill-slits open. It is plain,
therefore, that the epiblast has no share in the formation of the
gills, which arise as vascular processes of the walls of these
diverticula. Hight pairs of diverticula arise, of which the first
pair very soon disappear, and so far as I have been able to
discover, never pierce the skin at all; and I could not find
traces of them in larve more than a day or two old. The arch
of the first pair bears no gills, but its presence is very im-
portant for the proper understanding of the skeletal and other
parts of the head, as well as for the settling of the disputed
question of the systematic position of the Cyclostomata.
Professor Huxley? has described a hyomandibular cleft in quite
old larvee, but 1 have not been able to verify his observations
on this point.
The mid-gut is at first completely filled up with yolk-cells,
which do not begin to be absorbed until the larva has reached
a length of about 6 mm. In the front end more cells are ab-
sorbed, in the hind parts very few disappear, and the epithelium
of the alimentary canal is at first remarkably high, but
the cells gradually become very much flattened. A deep fold in
the wallof the mid-gut makes its appearance in larve of about
7 mm., in which fold there is a special aggregation of mesoblast
cells. This fold is the valve, and is very similar to the vaive
of Chimera as well as to the first rudiment of the spiral valve
in the Elasmobranchs.
The hind-gut is distinguished from the mid-gut by the
absence of the valve, and further by the circumstance that it
loses the yolk-cells, which fill it, at a very early period, while the
embryo is still unhatched, in adaptation to the function of the
excretory organs, which already develop an opening into the end-
gut and through the anus outwards.
In general it may be said that the alimentary canal suffers a
gradual degeneration in the course of development. The canal
is relatively largest and most important in larve of 7—10 mm.,
1 Benecke, quoted by Kupffer, ‘ Zoolog. Anzeiger,’ No. 59.
2 Huxley, ‘ Proc. Roy. Soc.,’ No. 157, p. 129.
PRELIMINARY ACCOUNT OF DEVELOPMENT OF LAMPREYS, 149
while it has become extremely small in the sexual animal,
and is almost obliterated by the enormously swollen genital
glands.
The mouth is one of the most peculiar organs of the entire
organism, and in its development, I believe, the key to many
of the peculiarities of the Cyclostomata is to be found. It arises
as a simple sinking in of the epiblast, which becomes gradually
deeper until it finally touches the hypoblast at the blind anterior
end of the alimentary canal. The next step is the perforation
of the two membranes, which seems to take place in the usual
way; but I have not been able to follow all the steps in the
process. The great peculiarities of the mouth-parts which we
have mentioned, lie in the lips, &c., which surround the cavity,
and will be more properly treated of in connection with the
mesoblast.
The epidermis is at first single-layered, and does not divide
itself into two layers until after the hatching of the larva.
The central nervous system has, so far as the earlier stages are
concerned, been carefully investigated by Calberla (‘ Morph.
Jahrb.,’ Bd. iti), and I can confirm his results in all points, except
that the division into two layers of the epiblastic cells concerned
in the formation of the cerebro-spinal axis does not seem to be
so clear as he made it out. A shallow groove appears in the
dorsal surface of the embryo, and the epiblast cells in the neigh-
bourhood of this groove begin to divide themselves rapidly into
two layers, and by their multiplication form a strong solid keel
which projects inwards towards the hypoblast. The keel is soon
detached from the general epiblast, becomes oval in section, and
upon the fourteenth day after hatching develops a lumen by the
separation of some of the cells. Such a peculiar formation of the
medullary cord is to be found only in the Teleosteans. Now, it
has been suggested by other investigators that the Teleostean egg
has undergone a reduction in bulk through the partial loss of
the food material. If we assume such a reduction in bulk in
the egg of Petromyzon, we shall be able to explain not only the
surprising correspondence of two such widely separated groups,
but also the presence of hypoblast cells in the roof of the seg-
mentation cavity in the egg of Petromyzon, which is supplied
with such a small amount of food material.
The drain arises at first as a club-shaped swelling of the
anterior end of the nervous axis, and is very small and simple.
Soon, however, the rudiment becomes divided by shallow con-
strictions into three divisions, of which the posterior is by far
the longest, the anterior the shortest. The walls of the b ain
are everywhere uniform ; thickenings and thinnings of separate
parts do not occur till a much later period. ‘The rudiment of
150 Ww. B. SCOTTY,
the cerebral hemispheres is a simple unpaired bud, which later
becomes divided into lateral halves. At first only a lateral
development of the extraordinarily small rudiment takes place,
so that the epiphysis lies between the hemispheres and almost at
the anterior edge of the brain. In the later stages, and especi-
ally after the metamorphosis, the cerebrum grows longer and the
epiphysis comes to lie behind it. The differentiation of the
olfactory lobes takes place comparatively late in larval life.
The epiphysis and infundibulum are diverticula of the roof and
floor respectively of the posterior part of the fore brain. The
pituitary body is developed as a solid cord of cells which are
invaginated from the epiblast, together with a single median
invagination for the olfactory pit. Only the posterior part of
this invagination is concerned in the formation of the pituitary
body. These cells soon lose all connection with the olfactory
apparatus, and become divided by connective-tissue bundles into
solid follicles; in the sexual animal the gland lies above the
naso-palatal passage.
In the mid-brain the lateral thickenings and thinnings of the
dorsal median line are especially to be noticed. This division
thus receives a bilobed roof. The brain is at first straight and
shows no tendency to flex itself. The cranial flexure never
attains a very great degree, about a right angle, and is partially
corrected by an actual extension in the reverse direction. There
is also an additional apparent correction which is caused by the
great development of the upper lip.
The rudiments of all the higher organs of sense appear during
embryonic life before the epiblast has divided itself into two
layers. The eye develops in essentials just as in the Gnatho-
stoma and needs no especial explanation. ‘The optic vesicle is,
however, remarkable for its length, and for the fact that only
a part of the anterior wall of the vesicle becomes the retina.
The lens arises as a local invagination of the single-layered epi-
blast. The auditory vesicle develops as an invagination of
thickened epiblast cells, which gradually deepens, becomes sphe-
rical, and detaches itself from the skin. Its later development
presents some details of interest; which, however, must be
reserved for the full paper.
The olfactory organs are, for Petyomyzon, of especial interest.
I cannot confirm Calberla’s! result as to the paired origin of the
olfactory pit, on the contrary, according to my observations (and
here I am in accord with Dr. Gotte, as he informs me by letter)
this pit is single from the very first. The first stage is a
shallow sinking in of the epiblast at the anterior end of the head
1 Calberla, ‘ Amt]. Bericht der 50 Versamml. d, deutschen Naturforscher,
&c.,? Munich, 1877, p. 188.
PRELIMINARY ACCOUNT OF DEVELOPMENT OF LAMPREYS, 151
immediately above the mouth; then the epiblast cells which
border the pit above are thickened and form a layer of epithe-
lium which is perfectly continuous, and takes up the whole of the
anterior part of the head. On account of the cranial flexure
this epithelium looks directly downwards. The pit becomes
gradually deepened, but the olfactory epithelium remains still
on the surface of the head; soon, however, it has a deeper posi-
tion, and shows only a small triangular opening on the exterior.
Late in larval life the epithelium of the olfactory organ develops
the well-known folds which show a definite paired arrangement.
The palato-nasal passage does not attain any considerable length
until after the metamorphosis; and its rudiment is from the first
single. The paired olfactory nerves show, however, that that
organ was at one time paired, and that a later fusion of the two
pits took place. If the two pits of the Sturgeon (O. Salensky,
]. c., Taf. 1x, fig. 84), which lie at the anterior part of the head
and not laterally as in the Elasmobranchs, were brought nearer
the middle line, we would have almost exactly the condition of
Petromyzon. But in the latter type the paired stage has been
over-lept in the course of development.
The mesoblast, in the earlier stages, has in general very much
the relations that are observed in the Elasmobranchs, or still
more like those of Triton ; but it is worthy of notice that in
Petromyzon the first pair of protovertebre follows closely upon
the auditory vesicles instead of leaving a considerable interval
free between them as in the Hlasmobranchs. The protovertebre
develop muscle-plates which gradually grow forwards and overlap
each other; the anterior ones grow over the head as far as the
olfactory capsule, and by processes of division develop the
muscles of the head. But since these myotomes belong mor-
phologically to the trunk they cannot be regarded as guides to
the segmentation of the head.
In the head the mesoderm undergoes another segmentation,
giving rise to one segment between every two gill-slits and two
in front of the first gill-slit, just as in the Elasmobranchs and
Urodeles. These segments surround a central cavity and cor-
respond exactly to what Balfour has called “ head-cavities.”’
These segments develop the gill muscles, and I believe the first
pair give rise to the muscles of the eye. In the trunk the
development of the mesoblast, its splitting formation of the
pleuro-peritoneal cavity, &c., shows no essential deviations from
the conditions found in the Elasmobranchs and Urodeles. The
internal muscles of the sucking-disc appear to develop them-
selves directly from indifferent mesoblast cells. The formation
of the sucking-disc is very striking, and its peculiarities appear
very early. At first the upper lip appears as a low rounded
152 WwW. B. SCOTT.
ridge, between the mouth and olfactory pit, which seen in
longitudinal vertical section, has the shape of a right-angled
triangle, the hypotenuse of which ibounded by the olfactory
pit. This stage is found in embryo of about the eighteenth
day. Invery small larve the lower edge of the ridge (7. e. the
edge next the mouth) has begun to grow very rapidly, and is
curved downwards and backwards. The mouth has still a com-
pletely ventral situation; the correction of the cranial flexure
brings it further and further forwards, and at the end of this
the upper lip, whieh is now still more lengthened, turns
about an angle of nearly 180°, so that the edge of the lip,
which formerly pointed directly backwards, now points directly
forwards.
This gives us the characteristic terminal mouth of the Cyclos-
tomata, the formation of which brings the olfactory pit to the
upper side of the head. According to Max Schultze’s results,
the mouth is fitted for its sucking function in almost the very
smallest larvz.
This peculiar mouth would, therefore, appear to be one of the
first deviations from the normal character which developed itself
- in this group, and the change which the mouth undergoes is
followed by, and I think the connection is a causal one, many
other alterations, e.g. the situation and fusion of the olfactory
organs. The change of the mouth into a sucking apparatus
makes necessary an alteration of the mechanism of breathing.
The water of respiration can no longer stream through the mouth
to the gills and out of the gill-slits, but must stream in and out
of the gill-slits; and this makes necessary a change in the
musclés and skeleton of the gill apparatus. These changes
cannot be discussed here, we can only indicate the general im-
portance of the formation of the mouth. In addition to the
modifications already mentioned, there must be remembered the
new formations, the supporting cartilages for the sucking-disc,
none of which are present until after the metamorphosis of the
larva into the sexual animal, as well as changes in the course of
the cranial nerves, which are easy to follow in the course of
development. In short, I jind im the change of form of the
mouth a key to the solution of the problem of the head and its
organs in the Cyclostomata.
Urino-genital system.—My observations upon the excretory
system are somewhat more complete than those of W. Miller
(‘Jen. Zeitschr.,’ B. ix), but they confirm all his results. The
“segmental duct ” (I use this term of Balfour’s to translate the
“‘ Kopfnierengang”) is formed as a solid cord in the lateral part
of the mesoblast, which is not taken up in the formation of the
protovertebre. This solid cord appears on about the fourteenth
PRELIMINARY ACCOUNT OF DEVELOPMENT OF LAMPREYS. 153
day of embryonic life; it soon shows a lumen, and anteriorly
opens into the pleuro-peritoneal cavity. At the anterior end of
this duct are formed a series of ciliated tubes opening by wide
funnel mouths into the body-tavity, and on the other side
by narrow tubes into the duct. A glomerulus is then formed on
each side of the mesentery, just as in the Amphibia, and the
whole organ thus developed is the head kidney (Miiller’s Vor-
niere). Although I cannot prove it with absolute certainty, it
is yet in the highest degree probable that the ciliated tubules
are a development of the duct itself. The duct empties into the
now empty hind gut even in the embryos. It is to be especi-
ally noted that the head kidneys form for quite along period the
only excretory apparatus of the larva, the first rudiments of the
Wolffian bodies not appearing until the larve have reached a
length of 9 mm. These rudiments are metameric involutions of
the peritoneal epithelium, at first solid, which soon become
hollow and open into the body cavity and the segmental duct ;
they differ from those of the Elasmobranchs in being lateral to
the ducts. As Miiller has shown, the head kidneys gradually
become atrophied and disappear.
The segmental ducts at first open separately into the hind gut
near the anus; shortly before the metamorphosis they come
close together and form a common canal. The anal opening
becomes longer, and finally a part of the hind gut becomes con-
stricted off and forms the sinus wrino-genitalis, and receives a
separate external opening. The wall of the sinus is perforated
at two points to form the abdominal pores.
My investigations upon the genital organs are yet far from
complete. As far as they have yet gone, they agree with the
results of Miiller. :
Princeton, Vovember 29th, 1880.
154. G. F, DOWDESWELL,
On some Arprarances of the Rev Bioop-corpuscies @f Man
and other Vurtesrata. “By G. F. DowprswenL, B.A.
(Cantab), F.C.S., F.L.8., &c.
Some time since, in examining the action of septic matter, I
observed that when blood of man or the dog was treated on the
warm stage of the microscope with an aqueous extract of putrid
muscle, the red corpuscles shortly exhibited a curious phenome-
non, throwing out from their surfaces numerous processes, which,
in some cases formed a rosary of minute beads, in others fine un-
divided filaments, generally terminating in one or more drop-
lets, and assuming a bifurcated or racemose appearance; they
were of very variable size and form, from mere diminutive glo-
bules or protuberances on its surface up to five or six times in
length the diameter of the corpuscle. These processes were
evidently contractile, sometimes, from a considerable length,
retracting suddenly into a globule, or being withdrawn entirely
into the substance of the parent corpuscle; the detached par-
ticles, too, would coalesce into one larger globule. After a time,
varying, according to circumstances, from a few minutes up to
half an hour or so, they all became detached, forming a number
of small spherical bodies of various size, undistinguishable from
Micrococci; or short slender filaments, identically similar in
appearance to Bacteria or Vibrios, and in incessant molecular
movement swarmed over the field of view. About the same
time, usually, the hull or stroma of the red corpuscles became
colourless and difficult to distinguish, for all the reagents with
which I obtained these processes dissolve out the hemoglobin.
In the finer filaments and minute globules any colouration is diffi-
cult to distinguish clearly, but when these coalesce into a larger
body the colour becomes apparent, and it is most evident in the
large processes which are formed in the blood of the frog,
under the action of a 5-per cent. solution of ammonium chromate
in the cold. When the colouring matter of the red corpuscles
is dissolved out, and they disappear, the processes are also lost to
sight ; but upon treatment of the preparation with magenta or
other staining fluid, both the hull of the red corpuscles and the
processes too, become stained, and again apparent. On first ob-
serving this phenomenon J was in doubt whether it was to be
regarded asa physiological and vital process, or merely as a
physical one. Shortly afterwards Francis Darwin’s paper on
the “ Protoplasmic Filaments of the Teasel’’! appeared, and it
seemed to me that there must be an intimate connection between
? This Journal, N.S., No, lxvii, July, 1877, pp. 245—272,
APPEARANCES OF THE RED BLOOD-CORPUSCLES., 155
the two phenomena, so essentially similar in character. I then
instituted a series of experiments with solutions of different
salts and various reagents, under different conditions, with a
view to ascertain the laws which regulate these appearances. I
subsequently found that the same processes in the red corpuscles
of the blood of man had been described and figured some years
previously by Dr. William Addison, F.R.S.! The results I ob-
tained myself agreed in the main with those described by him.
It is sufficient here to mention that I found they occurred most
readily, in the blood of mammals, when treated with a mixture of
one part of pale sherry wine and one part of a 10-per cent. solu-
tion of sod. sulph., at a temperature of about 98° Fahr., or
somewhat lower. The sp. gr. of this mixture is about 1°008,
and its reaction acid; on neutralisation it fails to produce any
processes from the red corpuscles. In an aqueous solution of sugar
2°5 per cent. sod. sulph. 10 per cent., alch. 15 per cent., and ac.
acet. 1 per cent., they are alsoreadily formed at about the same tem-
perature. By treatment with some sherry wines alone they are pro-
duced, though not very readily. A slight acidity of the reagent
usually favours their production, as does the addition of 10 to 15
per cent. alcohol ; though neither of these is absolutely essential,
and the variety of reagents and mixtures which produce them is
endless. According to the sp. gr. of the solution in which they are
produced, the temperature, and other circumstances, their form
and duration is modified. The temperature most favorable for
their production, in the larger number of cases, is somewhat
below 98° Fahr., and that in all the mammalia that I have ex-
amined alike ; above that temperature they are quickly dissolved,
and much below it,with most reagents, they are formed slowly and
imperfectly, if at all. A solution of urea, as first stated by Kol-
liker, and others after him, will produce these appearances in
the blood both of frogs and of mammals. This is most
readily effected by drying a drop of the solution upon a slide,
putting the blood upon this, and covering it. Salt solution,
0°6 per cent., as described in a recent paper, produces these
appearances well in defibrinated frog’s blood on the warm stage.
By this treatment, too, the nucleus of the red corpuscle is some-
times very clearly shown, and the reticular fibres which it con-
tains, with the limiting membrane which encloses it, in places
penetrated by the fibres, as recently described and figured by
Dr. Klein? in this Journal, and by Fleming,’ are very apparent.
1 This Journal, N.§., vol. i, 1861, pp. 81—89, and ‘ Proc. R. Soc.,”
vol. x, 1859, pp. 186—189.
2 Vol. xviii, N. S., 1878, pp. 814—339, and vol. xix, N. S., pp. 125—
175, and ib. pp. 404—420,
3 ‘Archiv fiir Mikros. Anat.,’? Bd. xvi, 1879, s. 302—436, Bd, xviii,
1880, pp. 151—259, :
156 G. F, DOWDESWELL.
A solution of picric acid shows the structure of the nucleus
well, and with this permanent preparations may be made. As
far as | am aware, the intimate structure of the nucleus of
the red blood-corpuscle has not been described, excepting by
Dr. Schmidt, in the blood of Amphiuma! and some other ani-
mals. He describes and figures the nucleus as granular, and
invests the corpuscle itself with a membrane, which, whatever
it may be in the case of Amphiuma, appears certainly not
to be so in other animals; its existence seems to be clearly
incompatible with the production of the above-described pro-
cesses, as much as with the well-known experiment of Dr.
Beale, of breaking up by pressure with the point of a needle,
on the covering-glass, a red corpuscle into several small drop-
lets. In frog’s blood, too, its absence seems clearly de-
monstrated by treating it in the cold with a 5 per cent. solu-
tion of ammon. chromate, when the corpuscles are at first little
altered in appearance, excepting that the nucleus becomes pale
and distinct. After some minutes protuberances appear on
different parts of the periphery of the corpuscle ; some of these
are then extended, and form long processes, two or three
times the diameter of the corpuscle, of very appreciable thick-
ness, and distinctly coloured ; the size of some of these amounts
to a material portion of the corpuscle, the membrane of which,
if if existed, must be ruptured by their protrusion, and would
be clearly apparent under an amplification of 1000 diameters or
upwards, but nothing of the kind can be seen. The processes
formed in this case are frequently retracted again completely,
even the largest of them, and the appearances are most in-
teresting and instructive ; after a very short time the processes .
disappear, are retracted or detached ; the corpuscles then become
circular and colourless. Under the influence of this reagent the
corpuscles seem to become more plastic than normally, in the
same manner as when subjected to heat.
As above-mentioned, I found that these appearances were first
recorded by Dr. William Addison, in 1861 (loc. cit.). He de-
scribes the action of acids and alkalis, of various salts, and other
reagents upon the blood. He obtained the processes in question
most readily by treating the blood upon the slide with sherry
wine, either by itself or with the addition of different salts, and
found that neither quinine, morphia, nor strychnine, added to the
preparation, nor even the vegetable alkaloids in large propor-
tions, prevented their appearance, but that a very small pro-
portion of bichloride of mercury did so effectually. Dr. Addison
gives a plate with the different forms of the processes admirably
figured, and his paper forms a very complete account of them.
1 ¢ Journ. R. Mic, Soc.,’ vol. i, 1878, pp. 57 and 97.
APPEARANCES OF THE RED BLOOD-CORPUSCLES. 157
In 1863 Klebs,! observing the blood of dead animals warmed
to bodily temperature, observed points projecting from the
surface of the red corpuscles, the larger of which often divided
into two parts, the corpuscles themselves becoming distorted.
The description is very meagre, and the appearances may be
little more than the prickly, or as it has been termed the hedge-
hog form of the corpuscles.
In the same year Rindfleisch? published some experimental
observations on the blood. He found that in extravasated
blood of the frog the red corpuscles became round, and a portion
of their’contents, as he describes it, protruded, forming fila-
mentous processes, or a rosary of red-coloured droplets, on the
surface of the corpuscles; these he considers are protruded
through pores or other openings in the cell-wall, the droplets
of which they consist being held together by a viscid substance.
He further states that these appearances may also be produced
by a concentrated solution of urea.
The first mention of the effect of urea on the red blood-
corpuscles which I have seen is by Dr. T. L. Huenefeld, in a
work published in 1840,? in which he describes the action of
a great number of reagents, and states that a solution of pure urea
does not seem to have much effect on the red blood-corpuscles of
man or ‘the pig, beyond that it dissolves out the colouring matter
very quickly, leaving only portions of the hull and the nucleus
visible.
In 1864, Dr. Beale* describes and figures the changes of
form in the red blood-corpuscles of man from heat, the pro-
cesses and appearances presented, though more varied than those
described above, are obviously of the same character. The
paper was written in support of the author’s theory of formed
and living matter. In the same year Preyer® describes the
appearances in extravasated blood of the frog on the warm stage.
Long processes are formed, and globules which become de-
tached and sometimes reunite with the parent corpuscle. He
remarks that the action of urea will produce similar appearances,
which only differ slightly in colour, and makes the observation,
that im the blood of frogs at breeding time, nuclei evidently
dividing are found; these he figures. The processes above
described he also finds in the blood of frogs on the warm stage
without any reagent.
1 *Centralblatt. f. ci. Medicinisch Wissen.,’ Bd. i, 1863, s. 851.
2 ¢ Hxperimentalen Studien iiber des Blutes,’ Leipsig, 1868.
3 ‘Der Chemismus in der thierischen Organisation,’ Leipsig, 1840.
4 This Journal, N. $., vol. xii, p. 32, 1865.
5 “Ueber Amcehoide Blut-Korperchen,” Virch. Archiv,’ Bd. xxx,
. 438, 1865. 4
Dw
158 G. F, DOWDESWELL.
The same appearances caused by heat are next described by
Max Schultz.1 He found that on the warm stage of the microscope
the changes of form commenced first at 52° C.in the blood of
man and various mammals, on reaching which temperature the
corpuscles immediately change and break up into many parts
of various sizes, and are dispersed, dancing through the serum
in lively motion, or throw out filaments of various lengths and
form, which too become detached and move about in the sur-
rounding medium, like Vibrios. Here also a plate is given,
the representations in which agree exactly with the appearances
above described as caused by the action of reagents, both
on the warm stage and in the cold. No one can doubt the phe-
nomena being exactly the same.
In 1871, Professor H. Ray Lankester, in an article upon the
structure of the red blood-corpuscles,* describing the effect of
various reagents upon them, records the pseudopodial-like pro-
cesses which occur in the blood of the frog on treatment by
ammonia gas, and the fluidity which it seems to occasion in
the human red corpuscles, resulting in the production of long
threads or processes from the corpuscles, and the separation of
minute particles from them. Drawings are given of these,
which likewise agree exactly with the appearances before
described.
Quite recently two papers describing these appearances in the
red blood-corpuscles have appeared, the one is by Dr. Rudolph
Arndt,’ who first endeavours to show that the nucleus which
occurs in the red blood-corpuscles of Fish, Amphibia, and some
other Vertebrata, is an artificial production caused by the action
of reagents or pathological changes, which has no existence
normally, though when formed it is an independent contractile
body, which shows amceboid movements (!) ; and that conse-
quently there is no integral difference between the ovoid red
blood-corpuscles of the Amphibia, &c., and the round corpus-
cles of man and other mammalia, which do not usually show any
nucleus, though he considers that by the action of reagents or
certain changed conditions, they too show nuclei of the same
nature as those of the ovoid red corpuscles, mere aggregations
of their protoplasmic constituents, as shown by Beetticher,* who
treated them with alcohol and acetic acid, or with a solution of
bichloride of mercury in alcohol; the appearances so induced,
however, if carefully regarded, can never be mistaken for identical
with the nuclei of the ovoid red corpuscles ; the latter, as already
1 ¢ Arch. f, Mikros. Anat.,’ Bd. i, s. 25, 1865.
2 This Journal, N. S., vol. ii, pp. 361—3$87.
3 Virchow, ‘Archiv f. Path. Anat.,’ Bd. lxxvii, H. 1, s. 7, 1879.
4 «Arch, f, Mikros. Anat., Bd. xiv, s. 73—94, 187g.
APPEARANCES OF THE RED BLOOD-CORPUSCLES, 159
mentioned, in some cases showing very distinctly, an elaborate
structure, a network of internuclear fibres, some of them per-
forating the limiting membrane, which is very distinct, and its
appearance quite inconsistent with its being merely a patholo-
gical change as asserted by the author; moreover, the appearances
caused by treatment after Beetticher’s methods have been clearly
and fully explained, and accounted for in a paper in a subse-
quent number of the same journal.! In some cases, too, the
nuclei may be seen clearly dividing, though as my own observa-
tions were made chiefly upon summer and autumn frogs these
instances were few. Preyer, however,” describes and figures this
division of the nucleus in the blood of frogs during the breeding
season. After discussing the question of the contractility of the
red corpuscles, and whether they possess a cell wall, in the
proper sense of the term, the author describes the appearances
which are the immediate subject of this paper. Following
Preyer, he first examined extravasated frogs’ blood, and found
numerous processes, short points, and long straight filaments, in
short, exactly the appearances above described; and mentions
their production similarly by the action of urea and of heat. Also
that similar processes are thrown out in cases of fever, especi-
ally typhus; and that with a bodily temperature of 39-40° C., they
occur at the temperature of the chamber; and in recurrent fever,
as first described by Haidenreich in 1871, long filamentous pro-
cesses of great length, extending over the whole field of the
microscope, appear. These have been regarded as independent
organisms, a form of Bacteria, and named Spirochete Obermeieri,
or Recurrentis, as which they are described by Cohn.? These the
author has observed sometimes to coalesce again with the parent
corpuscle, and disappear. On this account he regards them as
portions of the protoplasm of the corpuscle, which have become
detached and endowed with independent vitality and spontaneous
movement, but are not mere parasites. This view appears to be
well founded, and supported by the circumstance, previously
recorded, of their intermittent appearance in the blood, and that
when present in vast numbers under the microscope, they again
1 Tf the red corpuscles of human blood be treated with a five per cent
sol. amm. chromate, the superficial appearance of a nucleus is produced, at
least as-distinct as that which Beetticher’s methods create: the discs be-
come “cup-shaped,” or more accurately, the shape of a soft felt hat, with
the margin of the brim turned over, or under, all round; and as they float
about and turn over, it becomes evident that the colourless or pale appear-
ance of a nucleus is occasioned by the central portion of the layer of the
corpuscle, when lying flat and looked down upon, being seen single and
consequently pale.
2 Loe. cit., supra.
5 * Beit. z. Biol. d. Pflanzen,’ Bd. i, H. 3, 1875, s, 196.
160 G. F, DOWDESWELL.
shortly all disappear; and still further, by the fact stated by
Cohn (loc. cit.), that they are dissolved by potash, which is con-
trary to the properties of all known Bacteria, the resistance of
which to alkalis and acids is regarded as their chief and most
reliable characteristic. That they are portions of the proto-
plasmic substances of the corpuscle appears to be evident ; as
such they would possess contractility as long as they retained
the vital properties of protoplasm, though in such attenuated
filaments, the movements which they exhibit may be merely phy-
sical, the result of the currents which are never absent from a
preparation of blood under the microscope, unless it be sealed, or
until coagulation occur.
The next and latest description of these processes is in an ex-
cellent paper by Gaule,! which describes their appearances in defi-
brinated frogs’ blood, treated on the warm stage at a temperature
of 30° to 82°C. with a solution sod. chor. 0:4 to 0°8 per cent.; the
method here adoped for defibrinating the blood was by shaking
it up sharply in a mixing glass with salt solution and a little
mercury, which subsides and carries the fibrin with it; a drop
of the supernatant fluid is then placed on the warm stage, treated
with more salt solution, and sealed. The author describes the
formation of these processes from the large majority of the cor-
puscles; a staff-shaped body first appears in which some bright
granules or strie are visible, this elongates, becomes detached,
pointed at both ends, and commencing a spiral movement,
wriggles about over the field of view; coming in contact with
other blood-corpuscles it adheres to them, dragging them after it,
strongly resembling in appearance minute worms, but, as the
author observes, in outward appearance only, and not in their real
nature. In length these bodies equal about half the diameter
of a red blood-corpuscle, but their character varies with circum-
stances, the vigour of the frog, the strength of the solution, &c.
The author concludes that these are processes evolved from the
constituent protoplasm, the stroma of the corpuscle. I can
confirm the author’s results in all respects. I have not found it
necessary to defibrinate the blood to obtain these appearances,
though to do so, simply whipping it is sufficient; nor is it
necessary to seal the preparation, though this, by preventing
evaporation, may somewhat prolong their duration.
Similar appearances have been described in other protoplasmic
bodies, not only in the white blood-corpuscles, but in Amcebe
(Protozoa) too,” under the action of dilute salt solution ; in some
1 ¢ Archiv f. Anat. u. Physiol.,’ 1880, Th. ] and 2,s.41—57. “ Ueber
Wiirmchen,” ete., von J. Gaule.
2 Dr. Vincent Czernay, “ Beobacht. iiber Amceben.,” ‘ Arch. f. Mikros,
Anat.,’ Bd. v, 1869, s. 158—166.
APPEARANCES OF THE RED BLOOD-CORPUSCLES, 16]
instances filamentous, or nodular processes, long pseudopodia,
rosaries, or detached particles, were formed as in the case of the
red blood-corpuscles; these appearances occurred during
vitality, and on treatment with plain water the organisms regained
their normal appearance and movement.
Thus it will be seen that these appearances have been observed
and described by many during the last twenty years; that they
are one and all of essentially the same character, there can be no
doubt ; it appears to me—that is, that they are essentially pro-
cesses of the constituent protoplasm of the red corpuscles, a
phenomenon of its contractility. Many who have observed and
described the appearances seem to have been unaware that they
had previously been described by others, as I was myself when first
I noticed them; for this reason I have thought it would be useful
to collate and record the observations already made upon this
subject. The appearances are remarkable and highly interesting,
as affording evidence of the constitution of the red corpuscles ;
no one, | think, after watching their evolution as above described,
more especially under the action of ammonium chromate, can
hava any doubt as to their true nature.
VOL. XXI,—NEW SER, L
NOTES AND MEMORANDA.
Meduse and Hydroid Polyps living in Fresh Water.—
With reference to the interesting note on this subject in the
October issue of this Journal I should like to make a few
remarks. It is there said, ‘‘ Curiously enough, Mr. Romanes
has found that marine Meduse are not so injuriously affected
by brine as the Limnocodium is by sea water. The fact, how-
ever, is less astonishing when we remember that the percentage
of saline matter in solution in sea water is many hundred times
what it is in average pond water, whilst the strongest brine has
not a percentage of saline matter many times in excess of that
of sea water” (p. 483).
Now, this is certainly one way of looking at the matter, but
I doubt whether it is the fairest way. The percentage of salt
held in solution by “ average pond water” is really so small that
it probably exerts no physiological influence of any kind on a
Medusa, and, therefore, for purposes of physiological reasoning,
ought not to be considered as a unit for comparison with higher
percentages which do exert aphysiological influence. It ought
rather to be considered as a vanishing quantity or zero, so far,
at least, as the Medusz are concerned. Therefore, it seems to
me that a fairer unit to takeis the one which I hadin my mind,
although I did not explicitly state it, while writing my article to
‘Nature’ of June 24th, to which you refer. This unit.is the
percentage of salt which Limnocodium can tolerate for an in-
definite time without manifesting a change in any of its phy-
siological processes. What we want is a physiological, not a
chemical, test of the percentage of salt that we are to consider
as our unit, and this, it seems to me, can only be rendered by
estimating the percentage of salt that first begins to exercise
any perceptible influence upon the animal. This amount I found
to be about + per cent. ‘Taking, therefore, ordinary sea water
as having 3 per cent. of salt, and a saturated solution 36 per
cent., we have as our proportions +: 3::3:36; or1:15::
15: 180; or1:15::1:12. This shows that, if we take the
above as our unit, the estimated change of conditions which a
freshwater Medusa undergoes on being transferred to the sea
water is pretty nearly the same as that which a sea-water
NOTES AND MEMORANDA, 163
Medusa undergoes when transferred to brine of saturated
strength.
If, then, we desire to draw any comparison at all, and if there
is anything “astonishing” in the fact that a quickly fatal issue
follows in the one case, while no harm results in the other, I
should, nevertheless, still prefer adhering to the unit fixed by
physiological conditions rather than to that supplied by chemical
analysis.
In the same note of the ‘Quarterly Journal of Microscopical
Science’ there appears a very interesting statement by Mr.
Moseley, and another by Professor Agassiz, regarding the occur-
rence of marine Medusz in ‘‘ quite brackish,” or even “almost
fresh,” water. One remark made by Professor Agassiz in this
connection appears to demand some notice from me. He says:
“So far as my experience goes, it is not conclusive of so fatal
an action of fresh water on Medusze as Romanes would lead us
to believe in,” &c., proceeding to relate his own observations on
sundry species of Medusze which live in the estuary of the Charles
River. Now, as Professor Agassiz must have failed to refer to
the observations which he thus appears to stigmatise as inaccu-
rate, I will ask you to be kind enough, for his information, to
quote them in extenso. For this purpose I give below an
extract from the ‘Philosophical Transactions? in which they
occur, and from which it will be seen that I have made no
experiments or statements with reference to the effects of brackish
water, either in estuaries or elsewhere. My experiments con-
sisted merely in svddenly transferring Medusz from sea water
to perfectly fresh water. It certainly does surprise me to
learn that Sarsia, Tiaropsis, and Aurelia are able to thrive
in water tha} “tastes but little of salt ;” but the fact in no
way touches any of my published results. I can only con-
clude from it that a gradual transition from salt to comparatively
fresh water not giving rise to such rapid osmosis is not so in-
jurious to Medusz as I should have expected from the morbid
effects of sudden transition. The whole subject is thus shown
well worthy of further experimental inquiry; but, so far, the
following are the only experiments that I have conducted with
reference to it.—GzorcE J. RoMANEs.
Extract from ‘ Phil. Trans.,’ vol. 167, p. 744.
As fresh water exerts a very deadly influence on the
Medusz, this seems the most appropriate place for describing
its action. Such a description has already been given by
Professor L. Agassiz, but it is erroneous. He writes: “Taking
up ina spoonful of sea water a fresh Sarsia in full activity, when
swimming most energetically, and emptying it into a tumbler full
164 NOTES AND MEMORANDA.
of fresh water of the same temperature, the little animal will at
once drop like a ball to the bottom of the glass and remain for
ever motionless—killed instantencously by the mere difference or
the density of the two media.”! As regards the appearance pre-
sented by Sarsia wheu subjected to “this little experiment,”
‘ the account just quoted is partly correct ; but Professor Agassiz
must have been over-hasty in concluding that, because the animals
seemed to be thus “ killed instantaneously,” such was really the
case. Nothing, indeed, could be more natural than this con-
clusion ; for not only is the contrast between the active swimming
motions of the Sarsia in the sea water and their sudden cessa-
tion of all motion in the fresh water very suggestive of instan-
taneous death, but, a short time after immersion in the latter,
their contractile tissues, as Professor Agassiz observed, became
opalescent and whitish. Nevertheless, if he had taken the pre-
caution of again transferring the Swrsia to sea water, he wonld
have found that the previous exposure to fresh water had not
had the effects which he ascribes to it. After a variable time
his specimens would have resumed their swimming-motions ; and
although these might have had their vigour somewhat impaired,
the animals would have continued to live for an indefinite time—
in fact quite as long as other specimens which have never been
removed from the sea water. Even after five minutes’ immer-
sion in fresh water, Sarséa will revive feebly on being again
restored to sea water, although it may be two or three hours
before they do so; they may then, however, live as long as other
specimens. In many cases Sarsia will revive even after ten
minutes’ exposure; but the time required for recovery is then
very long, and the subsequent pulsations are of an exceedingly
feeble character. I never knew a specimen survive an exposure of
fifteen minutes. In not a few cases, after immersion in fresh
water, the animal continues to pulsate feebly for some little time ;
and, in all cases, irritability of the contractile tissues persists for
a little while after spontaneity has ceased. The opalescence
above referred to principally affects the polypite, tentacles, and
margin of the nectocalyx. While in fresh water the polypite
and tentacles of Sarsia are strongly retracted.
Thinking it a curious circumstance that the mere absence of
the few mineral substances that occur in sea water should exert
1 ¢Mem. American Acad. Arts and Sciences,’ 1850, p. 229.
2 The covered-eye Meduse survive a longer immersion than the naked-
eyed—Aurelia aurita, for instance, requiring from a quarter to half an
hour’s exposure before bemg placed beyond recovery. Moreover the
cessation of spontaneity on the first immersion is not so sudden as it is in
the case of the naked-eyed Meduse—the pulsations continuing for about
five minutes, during which time they become weaker and weaker in so
gradual a manner that it is hard to tell exactly when they first cease.
NOTES AND MEMORANDA, 165
so profound and deadly an influence on the nervo-muscular
tissues of the Medusz, I was led to try some further experi-
ments to ascertain whether it is, as Agassiz affirms, to the mere
difference in density between the fresh and the sea water, or to
the absence of the particular mineral substances in question,
that the deleterious influence of fresh water is to be ascribed.
Although my experiments led to no very instructive conclusion,
they are, I think, worth stating.
I first tried dissolving chloride of sodium in fresh water till
the latter was of the same density as sea water. Sarsie dropped
into such a solution continued to live for a great number of
hours ; but they were conspicuously enfeebled, keeping for the
most part at the bottom of the vessel, and having the vigour of
their swimming-motions greatly impaired. The tentacles and
polypite were strongly retracted, as in the case of exposure to
fresh water, and the tissues also became slightly opalescent.
Thinking that perhaps a fairer test would be only to add as
much chloride of sodium to the fresh water as occurs in sea
water, I did so; but the result was much the same. On now
adding sulphate of magnesium, however, to the amount normally
present in sea water, the Sarsie became more active. I next
tried the effects of chloride of sodium dissolved in fresh water
to the point of saturation, or nearly so. The Sarsze, of course,
floated to the surface, and they immediately began to show
symptoms of torpidity. The latter became rapidly more and
more pronounced, till spontaneity was qnite suspended.
The animals, however, were not dead, nor did they die for many
hours—their irritability continuing unimpaired, although their
spontaneity had so completely ceased. The tentacles and polypite
were exceedingly relaxed, which is an interesting fact, as being
the converse of that which occurs in water containing too small
a proportion of salt. Lastly, to give the density hypothesis a
still more complete trial, I dissolved various neutral salts and
other substances, such as sugar, &c., in fresh water till it was of
the density of sea-water; but in all cases, on immersing Sarsia
in such solutions, death was as rapid as that which followed their
immersion in fresh water.”
Terminology of Reproductive Organs and Classification of
Thallophytes.—Our readers are requested to substitute the fol-
lowing table for the one given on pp. 419, 420 of the last
number of the “ Journal.”
We take this opportunity of thanking many correspondents
for their kind and encouraging criticisms; and of making the
following corrections and emendations.
166 NOTES AND MEMORANDA,
The most recent investigations of the Chytridiacee point to
their systematic position among the Zygomycetes next to the
Mucorinis rather than among the Oomycetes. A corresponding
correction should be made on p. 409, lines 8—5 from bottom.
Berthold’s discovery of the conjugation of zoospores (zoozygo-
spheres) in Dasycladus, following the similar observation of De
Bary and Strasburger in Acetabularia, points to the probable
location of the whole family of Dasyc/adee among the Zygo-
phycere, near to Botrydiew, rather than among the Oophycez.
On p. 415, 1. 21 from bottom, “ Desmidiex’’ should be
Diatomacez.
On p. 418, 1. 21, the Uredineze and Ustilaginee should be
named, in addition to the Basidiomycetes, as Carpomycetes, in
which the sexual organs (at least the female ones) are at present
unknown.
Atrrep W. Bennett.
Grorce Murray.
Reproductive Organs of Thallophytes.
Female.
PROTOPHYTA.
MyYXxoMYCETES.
MocorinI. Zygogonium.
Zygosphere.
Zygosperm.
PERONOSPOREZ.
Oogonium,
Oosphere.
Oosperm.
SAPROLEGNIEZ.
UREDINES.
UStTILAGINER.
BASIDIOMYCETES,
ASCOMYCETES,
Carposphere.
Carposperm.
Trichogonium.
including LicHENnEs. Carpogonium.
Non-sexual,
Chlamydospore.
Sporangium.
Sporangiospore.
Zoosporangium.
Zoospore
Chlamydospore.
Sporangium.
Sporangiospore.
Conidiospore.
Zoosporangium,
Zoospore.
Zoosporangium.
Zoospore.
Teleutospore.
Sporidium.
Accidiospore.
Uredospore.
Teleutospore.
Sporidium.
Basidium,
Basidiospore.
Conidiospore.
Stylospore.
Ascus.
Ascospore.
Polyspore.
Merispore.
ZYGOPHYCEZR.
OoPHYCcEz.
CaRPOPHYCEX.
NOTES AND
Female.
Zygogonium.
Zygosphere.
Zoozygosphere.
Zygosperm.
Hypnosperm.
Oogonium.
Oosphere.
Oosperm.
Conceptacle.
Hypnosperm.
Trichogonium.
Carpogonium.
Carposphere.
Carposperm.
Cystocarp.
MEMORANDA, 167
Non-sexual.
Zoosporangium.
Zoospore.
Megazoospore.
Auxospore.
Hypnosporangium.
Hypnospore.
Parthenospore.
Zoosporangium.
Zoospore.
Parthenospore.
Androspore.
Hypnospore.
Zoosporangium.
Zoospore.
Tetraspore.
Octospore.
Carpospore.
MEMOIRS.
The Minute Anatomy of the BRacHIATE ECHINODERMS.
By P. Hersert Carpenter, M.A., Assistant- Master
at Eton College. With Plates XI and XII.
In the following pages I propose to give some account of
the work that has been done during the last few years upon
the minute anatomy of the Starfishes, Ophiurids, and
Crinoids. I do not intend to touch upon the question of
the skeleton at all, as I have already discussed its mor-
phology in the pages of this Journal. At present I aim
only at giving an intelligible account of what appear to be
well-established discoveries in the anatomy and physiclogy
of the nervous, vascular, and generative systems of these
three groups.
By far the most important of the recent researches in this
subject are those of Ludwig.? Others may have devoted
more attention to particular groups, but no one has worked
so extensively at increasing our general store of facts in
Echinoderm morphology as he has; while, at the same time,
his observations are by far the most accurate and trustworthy
of any that have been recorded. Although there are one
or two theoretical points with respect to which our opinions
are entirely different, I have no hesitation in saying that I
have the utmost confidence in his facts. There are, of
course, many anatomical peculiarities that were more or less
perfectly elucidated by his predecessors, but on the whole,
no one has done so much as he has towards correlating,
systematising, and verifying or correcting the more or less
conflicting observations of other investigators.
} “The Oral and Apical Systems of the Echinoderms,” ‘Quart. Journ.
Micr. Sci.,’ vols. xviii and xix. ‘‘Some disputed points in Echinoderm
Morphology,” ‘Quart. Journ. Mier. Sci.,’ vol. xx.
* Morphologische Studien an Echinodermen,” Leipzig, 1877—79.
These were originally published as separate papers in the ‘ Zeitschrift fur
Wissenschaftliche Zoologie,’ Bande xxviii, seqq.
VOL, XXI.——NEW SER. M
170 P., HERBERT CARPENTER,
Were it not for his work on the ‘Anatomy of theStarfishes,’
the observations of three other authors, which were published
in 1876, would only have increased the confusion that
already existed in this subject. This has, in fact, been
the case with respect to the Urchins and Holothurians,
though in a less degree, and it is now very desirable that
the minute anatomy of both these groups should be rein-
vestigated by the light of our present knowledge of the other
Echinoderms. It is more than probable that the results of
such investigation would necessitate the giving up of many
of our present ideas concerning the nervous and vascular
systems of these two orders.
It will perhaps be best if we commence our studies
with the Starfishes, which are probably the best known
among the Echinoderms. Having acquired some under-
standing of their typical structure, we can proceed to con-
sider that of the Ophiurids, and finally that of the Crinoids,
which presents many singular deviations from the ordinary
Kchinoderm type. I shall not attempt todo much more than
describe the actual anatomical facts, leaving almost entirely
out of consideration any identification of particular parts
with the structures mentioned by the older anatomists.
This (if required) must be sought for in the original me-
moirs themselves, a list of which is to be found at the
conclusion of this paper.
Figure 3 on Plate XI is a diagrammatic transverse
section, representing the structure of a Starfish arm. On
the left side the section is supposed to pass through a ver-
tebral ossicle, while on the right it passes between two suc-
cessive ossicles. The pyloric cecum (p.c.) is omitted from
the left side for the sake of clearness, while on the right the
genital gland (ov.) is not represented. The integument
lining the ambulacral groove between the rows of tube feet
differs considerably from that covering the rest of the exte-
rior of the body. It is usually more or less raised into
a median ridge, and consists of two principal layers, an outer
cellular and an inner fibrillar one. The latter (figs. 3 and
5,.) is thickest in the middle line, but thins away laterally,
while the former (a.e.) is merely a modified portion of the
general external epithelium of the arm (E), with which it
is continuous at the sides of the groove. This ambulacral
epithelium consists of columnar cells, each bearing cilia,
which seem to pass through delicate pores in the superficial
cuticular layer. The cells are closely packed, and their
nuclei are situated at different heights, so as to produce the
appearance of there being several different layers of cells
MINUTE ANATOMY OF THE BRACHIATE ECHINODERMS, 171
(17, 21).1. The cell bodies are supported upon long rods, the
bases of which are often forked, and rest upon the connec-
tive-tissue membrane that separates the ambulacral epi-
thelium from the vascular apparatus above it (fig. 5, ct.).
Between these vertical rods lie the longitudinal fibres of the
subepithelial layer (.), to which a nervous character is
generally assigned (21, 33). Intercalated among the fibrils
are small masses of nucleated protoplasm, which are con-
tinuous with their substance, and sometimes mark the points
atwhich they divide. Ludwig regards these small cells as
nerve-cells, but they escaped the notice of Lange, who was
consequently led to assign a nervous character to a cellular
layer on the upper (?. e. dorsal) side of the above-mentioned
connective-tissue membrane (fig. 6, ep.).
The observations of Ludwig and Teuscher, however, prove
that Lange’s masses of nerve-cells are merely local thicken-
ings of the epithelium lining the radial perihzemal canals.
They are not constant in all Asterids, and when present are
not continuous through the ray. A similar thickening in
the peristome of Asteracanthion rubens is represented in
fig. 6, ep.
Above and within the nerve band is the blood-vascular
apparatus of the ambulacrum, which is very complicated in
its arrangement. Between the basement membrane support-
ing the ambulacral epithelium (fig. 5, ct) and the band of
connective tissue that bears the lower transverse muscles of
the arm, immediately under the water-vessel, is a relatively
large space, which extends through the whole length of the
ambulacrum. It is divided into two lateral portions by a
perforated vertical septum, also longitudinal (fig. 5, v.s.), which
supports the radial blood-vessel (fig. 3, d.). The latter, which
is often somewhat plexiform in character, was more or less
perfectly known to Hoffmann, Greeff, Lange, and Teuscher,
but its true relations were first elucidated by Ludwig. The
space already mentioned (fig. 3, 7.p.) between the water-vessel
above and the ambulacral epithelium below, which is tra-
versed by the perforated longitudinal septum, was named by
Ludwig the “ perihemal canal.” It had been previously
called the nerve-vessel or nerve-canal, and was supposed to
form an integral part of the blood-vascular system.” Now,
1 The numbers in brackets refer to a list of recent memoirs on Echino-
derm anatomy, which is printed at the end of this paper.
2 In his “Anatomy of the Invertebrata” Prof. Huxley speaks of the
periheemal canal as the ambulacral neural canal, and expresses great doubt
as to whether it really belongs to a special system of blood-vessels, The
later observations ef Ludwig render the old view no longer tenable.
172 P. HERBERT CARPENTER,
however, it is regarded by Ludwig merely as a derivative of
the body-cavity. At the intervals between the successive
vertebrze its upper third is crossed by a series of transverse
septa (fig. 5, ¢.s.). The longitudinal septum has a slight
horizontal expansion at the level of the radial blood-vessel,
which increases in size at the origin of each transverse
septum, but never reaches the side of the perihzemal canal.
Hence the latter is nowhere completely divided into three
or four sets of chambers, as was formerly supposed. It gives
off lateral extensions, which embrace the bases of the tube
feet, and unite on their outer sides to form longitudinal canals
(21). These, which were formerly regarded as lateral
auxiliaries of the radial blood-vessels, are in connection with
an extensive lacunar system in the body wall (fig. 3, dac.),
which can be injected from the radial perihemal canal,
and appears, like the latter, to be a derivative of the body-
cavity, or perhaps, of the embryonic blastoceel.
In the peristomial area of the disc the radial, nervous,
and vascular trunks unite into their respective oral rings
(Pl. XI, figs. 5,6, 8). The nerve-ring (#.7.) in the lip
contains circular fibres packed among the rod-like bases of
the epithelial cells. The basement membrane which sup-
ports them also forms the wall of the perihzemal ring-canal,!
into which there project the cellular masses described by
Lange as nervous (fig. 6, ep.). The ring-canal itself is
divided into two parts, an inner and an outer one, by an
annular continuation of the longitudinal vertical septum in
the radial canal (figs. 5, 6, 8, s.). This is situated rather
obliquely, and supports the oral blood-vascular plexus (0. 0.).
The inner canal (7. p.) is the oral blood-vascular ring of
Tiedemann, while the outer one (0. p.) is the orange-coloured
vessel described by him. ‘The latter is connected by inter-
radial canalicular extensions with a widely-spread canal
system, situated between the two layers which form the
body wall, just as in the arms. This system is also con-
nected, as will be seen later on, with the perihemal canals
surrounding the genitai vessels (12, 21). Both the inner
and the outer perihemal ring-canals have received various
names from Greeff, Hoffmann, Teuscher, and Lange, who all
regarded them, together with their radial extensions, as
integral parts of the blood-vascular system. The real oral
blood-vascular ring was seen by Tiedemann, Greeff, and
Teuscher, but its true relations were only imperfectly
known to them. Greeff conjectured what Ludwig has since
1 This is the “circular neural canal’? mentioned in Huxley’s ‘ Inverte-
brata.’ ‘
MINUTE ANATOMY OF THE BRACHIATE ECHINODERMS. 173
demonstrated, viz. the connection of this ring with a large
plexiform bundle of vessels (figs. 2, 7, 8, c.p.), which ascends
by the side of the stone-canal (s.c.) and joins an aboral
blood-vascular ring (fig. 2, @..). This organ was disco-
vered by Spix, and described by Tiedemann as a heart or
heart-like canal, by Hoffmann as a glandular body, by Greeff
as a gill-like organ, and then again as a heart by Teuscher
and Ludwig, though the latter author has since abandoned
the use of this term for the Echinoderms generally, and now
speaks only of the central plexus. The organ in question
is enclosed, together with the stone-canal, in a large tubular
space, which is supported by one of the interradial falciform
bands (figs. 7 and 8, a. p.). A person standing in the dorso-
ventral axis of the Starfish with his feet in the oral ring,
and facing the stone-canal, would see the central plexus to
the right of it. It consists (21, 33) of a close network of
vessels, partly dividing and partly anastomosing, the walls
of which contain connective-tissue fibres, and perhaps
muscle fibres also. The lumina of the vessels of the central
plexus, and likewise of those in the oral and aboral rings
connected with it, are filled up by large, brownish, cellular
bodies of a peculiar character, which are also described as
occurring in the celom and in the water-vascular system.
Tiedemann described the central plexus as responding to
stimulation by feeble contractions, and Hoffmann observed it
contracting rhythmically, the same peculiarity characterising
the two smaller plexiform bundles (fig. 2, p. 6.) which pro-
ceed to the stomach from the aboral ring at the point where
the central plexus joins it.
The central plexus, like the rest of the blood-vascular
system, is surrounded by a perihemal canal, which is the
tubular space mentioned above as enclosing the central
plexus together with the stone-canal (figs. 7, 8, a. p.). It
may be termed the axial perihzmal canal. Its central end
has been shown by Teuscher and Ludwig to arise from the
inner perihemal ring-canal (figs. 5, 6,8, ¢.p.). This is
only separated by a perforated septum (s) from the outer
perihzemal ring (0. p.) which unites the perihemal canals of
all the rays.
The so-called “heart” was described by Tiedemann as
terminating dorsally in an aboral vascular ring, from which
proceed (1) ten genital vessels, (2) ten vessels to the pyloric
ceca, (3) two gastric vessels, the plexiform bundles men-
tioned above. These results were confirmed by Greeff and
Hoffmann, except as regards the supposed vessels of group
(2). These had been previously shown by the late Professor
174 P, HERBERT CARPENTER,
Sharpey to be merely the spaces between the two folds of
mesentery in which each pyloric cecum is slung (fig. 3, m.).
They are only partially separated portions of the general
body cavity with which they are connected in the disc.
Greeff, Hoffmann, and Teuscher were able to inject the
tubular space enclosing the “heart”? and stone-canal from
this aboral ring described by Tiedemann; and Greeff
described the lumen of the ring as partially filled up by a
hollow fold, which exhibits the same structural characters
as the “heart” and the gastric vascular bundles. As in
the case of the oral ring, the hollow fold discovered by
Greeff in Tiedemann’s anal ring has been shown by Ludwig
to constitute the true aboral ring or annular plexus. It is
more or less filled up with the brown cellular elements
already mentioned as occurring in the central plexus, the
dorsal end of which joins it (fig. 2, a. 6.). The space around
it is no part of the true blood-vascular system, as supposed
by Tiedemann and Greeff, but the perihemal canal corres-
ponding to the aboral blood-vascular ring. This of course
explains the injection of the tubular space from Tiedemann’s
ring, as it is merely the perihemal canal of the central
plexus which joins the true aboral ring, but does not terminate
in it; for it passes upwards and attaches itself to the under
surface of the disc just outside the madreporite (fig. 2, 2).
Just in the same manner the structures hitherto described
as the two gastric vessels are merely the perihemal canals
corresponding to the real vessels which they enclose
(fig. 2, p. b.). The ultimate ramifications of the latter are
not known, but they contain the same brown cells as the
rest of the blood-vascular system.
Up to the time of Ludwig, the true vessels of the genera-
tive organs had never been properly observed ; the structures
described under that name by Tiedemann and others being
merely their perihemal canals. They are ten in number,
arising from the aboral ring (fig. 2, g. v.), and each expand-
ing into a sinus around one of the spreading genital glands
(fig. 8,g.). The perihemal canals enclosing them, which
start from Tiedemann’s ring, are directly connected with
the lacunar system in the body wall.- Hoffmann was led
to suppose that in the Starfishes devoid of the interbrachial
genital eat described by Miller and Troschel, the
perihemal canals are in immediate connection with the
internal cavities of the glands, the blood having direct
access to the follicles. He imagined these canals to serve
as ducts, the ova passing along them into Tiedemann’s
ring, thence into the tubular space and out to the exterior
MINUTE ANATOMY OF THE BRACHIATEcECHINODERMS. 175
through the pores in the madreporite. Greeff recognised
that the so-called genital vessels (¢.e. periheemal canals)
surrounded the glands; but he supposed the glands to open
intothem,and that the sexual products passed out by the inter-
brachial pores, which would thus place the blood-vaseular
system in direct communication with the external water.
Ludwig’s later observations have shown that definite
genital openings are present in all Starfishes, varying in
number from ten upwards. They sometimes extend out on
to the arms, so that the presence of individual openings for
the numerous separate glands in the arms of Brisinga is
no longer such a striking peculiarity as it was formerly
Supposed. Each genital pore (fig. 8, g.p.) leads into a
distinct efferent canal, which pierces the perihzemal canal
and its contained vessel, and enters the cavity of the gland,
to which it serves as a duct. In most cases these pores
are on the dorsal surface of the arm, but in Asterina
gibbosa they are ventral (25).
It will be seen from what has been said above, that the
pores of the madreporic plate were supposed by Hoffmann
to lead into the tubular space around the stone-canal as well
asinto the stone-canal itself. He likewise believed the marginal
pores of the madreporite to lead directly into the celom.
This connection of the water-vascular and the blood-vas-
cular systems through the pores of the madreporite with
the exterior and with one another was also believed in by
Greeff and Teuscher. Their views rested principally upon
the results of injection not checked by the section-method,
which are necessarily liable to much error. Ludwig, how-
ever, after making sections in three planes through the
madreporic plate, satisfied himself of the truth of the older
views of Sharpey, L. Agassiz, Miiller, and Tiedemann,
viz. that the pores of the madreporite lead simply and
soley into the stone-canal. The interior of the plate is
traversed by pore canals, which correspond in position with
the radiating furrows on its upper surface, and communicate
with them by short vertical tubules. These are lined by a
pavement epithelium, which becomes columnar and ciliated
at their openings on the surface, and likewise in the actual
stone-canal itself, into the top of which the radial pore
canals open (fig. 7,p.). At the aboral edge of the attach-
ment of the stone-canal to the madreporite is a lateral
diverticulum of the former, into which some of the collect-
ing tubes of the madreporite open (12, 21). It is occa-
sionally double or even triple, but its wall.is never calcified
like that of the stone-canal, and it is lined by pavement
176 P, HERBERT CARPENTER.
epithelium. On the other hand, the epithelial cells lining
the stone-canal are high and ciliated, and its walls more or
less plicated, in some species very much so; the plications being
supported by calcareous rings of various forms. Towards
its ventral end all the plication ceases and it joins the
water-vascular ring as a simple tube. So far as we know
with certainty, the water-vascular and blood-vascular
systems are entirely distinct, though the injections of Hoff-
mann and Greeff have led them to believe in a communi-
cation between the two systems in the region of the disc.
At any rate the old view, which was based chiefly on the
results of injections, is no longer tenable, viz. that the two
are connected by the ten “ brown bodies of Tiedemann,”
small eminences resting on the water-vascular ring (fig. 6,7).
Ludwig finds these structures to be lateral diverticula of
the water-vascular ring, which are lined by an epithelium
of cuboid cells, and contain the brown cellular bodies that
have been described as present in the blood-vascular system.
But there is no connection between these diverticula and
either the perihzmal ring- canal (fig. 6, @. p., 0. p.) or the true
oral blood-vascular ring {o. d.).
The origin of the lateral trunks from the radial water-
vessels is protected by a valvular arrangement discovered by
Jourdain, the effect of which is to prevent a reflux into the
radial vessels after contraction of the ambulacral vesicles for
the purpose of expanding their corresponding tube feet.
Lange and Ludwig have found this structure to be univer-
sally distributed in the Asterids, and Ludwig describes it
as also present in Ophiurids, and in some Urchins (16, 17,
21, 27).
Although Sars’ observations had led him to believe that
Brisingais entirely devoid of a special blood- vascular system
distinct from the celom, Ludwig has shown that in this as in
other structural characters it is a true Asterid, having a
dorsal and ventral ring and a central plexus connecting
them. This organ was known to Sars, together with the
perihemal space around it, and also the oral perihemal
ring with its radial prolongations, but he did not regard
the latter as in any proper sense entitled to be called blood-
vessels, while he altogether denied the existence of any aboral
blood-vascular system.
2. Ophiuroidea.
The minute anatomy of the Ophiurids has been inves-
tigated by Lange, Teuscher, and Simroth, and most recently
MINUTE ANATOMY OF THE BRACHIATE ECHINODERMS. 177
by Ludwig, who has shown that they correspond closely with
the Asterids in the essential details of their organisation.
Miiller’s discovery of the madreporic opening on one of
the mouth shields of Ophioglypha lacertosa, which has been
generally overlooked, has been confirmed by Ludwig and
extended to other Ophiurids. There is usually only one
pore which leads into a bent canal with lateral diverticula,
and lined by ciliated epithelium. Some Ophiure and many
Euryalids have several pores on one mouth shield, while in
Trichaster elegans there is one pore in each interradius (22).
Above the madreporite lie the stone-canal and central
plexus, which are together enclosed in a perihemal space
that, with its contents, was described as the stone-canal by
Miller and Teuscher. The real stone-canal (water-tube),
which was first recognised as such by Simroth, is lined asin
the Asterids by a ciliated columnar epithelium, and it opens
just above the madreporite into an ampulla-like cavity lined
by pavement epithelium. Ludwig believes the pore canal of
the madreporite to open into this space as its fellow does in
the Asterids, but he has never been able to prove it, though
he has demonstrated the connection of the upper end of the
water-tube with the water-vascular ring (Pl. XI, fig. 4, w.r.).
This bears either no Polian vesicles at all, or four, one for each
of the remaining interradii (P.), or numerous blind tubular
diverticula of various shapes, which are merely modified
Polian vesicles (27, 29,32). In most cases the ring gives off
bifurcating trunks which supply the large buccal feet (0,f’.).
The blood-vascular system of the Ophiurids, like that of
the Asterids, consists of dorsal and ventral rings united by
a central plexus (Pl. XI, fig. 1). The former sends off
branches to the genital glands (g. v.), while from the latter
there arise the radial blood-vessels (figs. 1 and 4,0.). These
last were discovered and correctly described by Lange, but
Teuscher at first supposed them to be parts of the nervous
system. They lie immediately above the nerve band (fig.
4, n.), and send off branches to the tube feet which are
accompanied by nerves. Between the blood-vessels and the
water-vessels of the arms are the perihemal' canals of the
former (fig. 4, 7. p.), which are connected laterally with the
contracted remnants of the extension of the body-cavity
into the arm that remain between the body wall and the
vertebre (27, 32).
In the disc the radial perihemal canal communicates as
in the Asterids with the outer of the two perihemal ring.
Neural canals, Huxley,
178 P, HERBERT CARPENTER,
canals, which has been hitherto described as the blood-vas-
cular ring (fig. 4, 0. p.). The real oral ring, however, from
which the radial vessels originate (0. 6.), is in close connec-
tion with the nerve ring (m. 7.) and joins the upper end of
the central plexus, which ascends from the mouth shield
alongside the water-tube. As already mentioned, these two
are enclosed within a perihzemal space which is connected
with the inner perihemal ring-canal, just as is the case with
the axial perihemal canal of the Asterids. Its other end
opens into the perihzemal canal of the aboral ring (fig. 4,
p-h.), the disposition of which is very singular. Although
naturally belonging to the dorsal portion of the disc, only
a part of it is to be found there, viz. those sections of the ring
which lie beneath the radial shields (fig. 1, a. 05.; fig. 4, a. 6.).
Resting on the mouth shields in the five interradial spaces
are five other sections of the ring (a. 0,.), with one of which
the central plexus is connected. The five radial and dorsal
sections are connected with the five interradial and ventral
ones by ten descending limbs, which pass downwards at the
sides of the rays (fig. 1, a. 6,). Just before leaving their
dorsal position these give off the ten principal genital vessels
(fig. 1, g..), branches from which surround the glandular
czeca situated between the genital clefts and the rays. The
ceca, which are situated between every two clefts, receive
their blood supply by lateral branches of the ten descending
limbs at the sides of the rays (a. 6,). All the separate cca
are connected by a cellular cord concealed within the vas-
cular ring, which is regarded by Ludwig as a sterile portion
of the generative apparatus comparable to the so-called
rachis of the Crinoids.
It has been hitherto supposed that the genital glands of
the Ophiurids ‘pour their products into the peritoneal
cavity, which communicates freely with the exterior by ver-
tically elongated apertures placed interradially on its
margins.” Ludwig’s observations, however, show that this
view, which was advocated chiefly by Miller, does not
altogether agree with the facts. He confirms the earlier
discoveries of della Chiaje and Rathke, to the effect that
the so-called genital clefts lead into a sac situated within
the celom but not communicating with it, and receiving
the ducts of the genital glands. There are ten of these
“burs” in the disc, two in each interradius, which lie close
alongside the radial skeleton (fig. I, 8). Hach is a thin-
skinned invagination of the body wall, the adradial lower
portion of which is supported by one of the so-called genital _
' Huxley’s ‘ Invertebrata,’ p. 504.
MINUTE ANATOMY OF THE BRACHIATE ECHINODERMS, 179
plates (Bu’.); while the abradial margin of the cleft is formed
by a continuation of the general scaly covering of the ven-
tral perisome (Bu’’.), The walls of the sac sometimes contain
small calcareous plates. Into each bursa open the isolated
Fig. 1.—Diagrammatic vertical section across a radius of an Ophioglypha
near the edge of the disc. Kd. dorsal; Kv. ventral body-wall; MZ.
radial diverticulum of the stomach; 4. portion of the arm included in
the dise; B. bursa; Bw’. the adradial edge of the bursal cleft, with the
bursal (genital) plate; Bw’, its abradial edge, with the scales of the
ventral perisome ; G. genital tubes. The arrows point to the bursal
clefts. (Copied from Ludwig.)
genital tubes (G.), some of which occupy the space between
it and theray, while others are situated on its abradial side,
extending nearly up to its dorsal surface. Each tube is
surrounded by a blood space, which is derived either directly
from the aboral ring, as in the case of the abradial tubes, or
from the genital vessels (adradial tubes). The genital pro-
ducts are not set free into the body-cavity, as was formerly
supposed, but merely into the burse from which they
reach the exterior. It is possible that the burs are also
respiratory organs, serving the same purpose as the external
respiratory ceca of the Asterids; while in some viviparous
species they serve as marsupial cavities.!
Among recent Hchinoderms there is no structure at all
comparable to these burse of the Ophiurids, but Ludwig
points out their resemblance to the hydrospires of the Blas-
toids, and especially those of Orophocrinus (Codonites). In
this genus the hydrospires have no special spiracular
openings at the apex as in Pentremites. There are also
1 Studer has recently pointed out (‘ Zool. Anzeiger,’ No. 67, p. 526) that
he described these bursz as marsupial pouches as long ago as 1876 (‘ An-
tarkt. Kchinodermen. Monatsber. d. Berlin. Akad.,’ 1876). In Ophiomyaa
vivipara every pouch contains two or three fully-developed young starfishes,
each enclosed in a thin membrane like a chorion. Ophiacantha vivipara
has fourteen clefts aud the same number of pouches, in each of which
there may be three young ones.
180 P, HERBERT CARPENTER.
no rows of pores at the sides of the ambulacra. But the
hydrospires communicate with the exterior by ten inter-
radial slits, which extend along the sides of the ambulacra
very much as the bursal clefts do in the recent Ophiurids.
The abradial walls of the burs also exhibit traces of the
plicated structure which is so characteristic of the hydro-
spires of the Blastoids. This comparison is one of great
interest from many points of view, but a discussion of the
questions it involves would be out of place here.
Miiller’s views respecting the nervous system of the
Ophiurids, although attacked by Lange, have been abun-
dantly confirmed by Teuscher, Simroth, and Ludwig. All
these four observers describe a band of tissue (fig. 4, 2) which
lies immediately above the under arm plates (S;—S,, &c.),
and is composed of two layers, an outer cellular and an inner
fibrillar one. Lange considers this to be merely a portion
of the integument, and has described as nervous a so-called
ganglionated cord lying above it, very much as he did in
the case of the Asterids. The other observers have shown
the untenability of this view, the “ganglion cells”? being
merely portions of the epithelial wall of the perihemal
canal, while the “ longitudinal commissures”’ are portions
of the membranous septum which separates the latter from
the real nerve band. JHach radial nerve gives off two
branches to the burse, which leave it just on the aboral side
of the origin of the nerves proceeding to the second pair of
buccal feet. The radial nerves are connected in the disc
with an oral ring (27, 29), which is immediately contiguous
to the blood-vascular ring and to the outer oral perihemal
ring-canal (fig. 4, ”.7.). With the latter are connected five
interradial spaces, one of which lies on the adoral side of the
external interradial muscle of every oral angle, and is con-
nected with the celom. Separated from the outer ring-
canal by a septum! is the inner one (fig. 4, ¢.p.), from
which arises the axial perihemal canal that encloses the
central plexus and sand-canal, just as is the case with its
fellow in the Asterids. The perihemal systems of the two
groups are essentially similar, except that the Ophiurids
lack the lacunar system which is so abundantly developed
within the integument of the Asterids.
1 It is evident from fig. 4 that the inner and outer perihemal ring-canals
ot the Ophiurids are much more distinctly separated than they are in the
Asterids. The former is separated from the body-cavity by the septum
marked s, which must not be confounded with the perforated septum
within the ring-canal of the Asterids; that supports the oral blood-vas-
cular ring (figs, 5, 6, 8, s), ;
MINUTE ANATOMY OF THE BRACHIATE ECHINODERMS, 18]
3. Crinoidea.
The Crinoids occupy a very curious position among the
Echinoderms. There are certain structural peculiarities in
which they resemble the Starfishes much more than the
Holothurians do, and yet they possess a complicated system
of organs which is absolutely without parallel in the other
Echinoderms.
The ambulacral epithelium lining the food grooves is
essentially similar to that in the ambulacra of the Star-
fishes. It consists of closely packed columnar cells, each
with a cuticle and numerous cilia. Their lower ends are
pointed and are apparently connected with some vertical
fibres, among which lie the longitudinal fibrillar bundles of
the ambulacral nerve. These vertical fibres, which arise
from the thin membrane separating the nerve and radial
blood-vessel, are probably merely of a connective-tissue
character. Sometimes in Antedon Eschrichtw there is a
second connective-tissue lamella which separates the nerve
from the epithelium above it, and supports the lower ends
of the epithelium cells (Pl. XII, fig. 10, 7.), but its presence
does not appear to be constant.
Intercalated among the longitudinal fibrils are many very
minute cells, just as in the ambulacral nerves of the Star-
fishes and Ophiurids, which have a close histological resem-
blance to the sub-epithelial bands of the Crinoids. Lateral
branches proceed from the ambulacral nerve to the succes-
sive tentacular groups, but there are no representatives of
the muscle nerves which occur in the Ophiurids.
Between the water-vessel and the ambulacral nerve the
middle line of the arm (or pinnule) is occupied by the radial
blood-vessel, just as is the case in the Starfishes (Pl. XII,
figs. 9,10, 11, 0.), but it is not enclosed in any perihemal
space, and is usually of very small size, so as occasionally to
escape notice altogether. On the other hand, it is sometimes
relatively very large, asin Actinometra nigra. Immediately
beneath it is the radial water-vessel (figs. 9—11, w.), from
which lateral branches proceed alternately on opposite sides
of the arm to the different tentacular groups, each branch
being accompanied by corresponding ones from the blood-
vessel and ambulacral nerve. The three radial trunks are
continued over the disc (figs. 14, 15) to the peristome, where
they unite into their respective circumoral rings.
Depending from the water-vascular ring into the body-
cavity are a number of small tubules, open below and lined
by ciliated columnar epithelium (fig. 14, w. ¢.). Their number
182 P, HERBERT CARPENTER,
varies considerably in adult Comatule, reaching thirty or
more in each interradius of Antedon rosacea ; but in Rhizo-
erinus and in the young Antedon there is but one in each
interradius (20), while in the early stages of the Pentacrinoid
larva of Antedon there is only one, which is always situated
in the same interradius as the foregut (26). Corresponding
to these water-tubes (“ Steinkaniale,” Ludwig), the ventral
perisome, whether soft or plated, is pierced by a variable
number of water-pores, which lead from the exterior directly
into the body-cavity (figs. 14, 15, w. p.). They are the
external openings of small canals lined by columnar epithe-
lium, and expanding almost immediately into enlargements
in which the epithelium is ciliated. The inner end of the
canal beyond the enlargement is lined by pavement epithe-
lium, and opens into the body-cavity. The number of these
water-pores is very large, but very variable, and they are
not limited to the disc, for I have found them on the lower
parts of the arms (fig. 15), and even on the proximal pin-
nules. In both these cases they open into that section of
the body-cavity which surrounds the generative apparatus,
and is known as the genital canal. Ludwig has estimated
their number in the adult Antedon rosacea at about 1500,
while in the young Antedon and in Rhizocrinus there is but
one in each interradius (20), and in the Pentacrinoid larva
there is only one which pierces the lateral margin of the
oral plate that is in the same interradius as the single
water-tube (26).
By means of the water-pores, body-cavity, and water-
tubes, therefore, the ambulacral system of a Crinoid is
placed in communication with the external water; and
Ludwig regards the water-pore and water-tube together as
conjointly representing the madreporic apparatus and stone-
canal of the Starfishes and Ophiurids. A multiplication of
these organs may occur in both groups, which is merely
carried somewhat further in the Crinoids, and the nature of
the epithelial lining of these afferent channels is the same in
all three groups. It remains, however, yet to be proved
that the disconnected water-pore and water-tube of the
Antedon larva are morphologically equivalent to the stone-
canal and madreporic apparatus of the other Echinoderms,
though it is certainly exceedingly probable that they are so.
At present we do not know enough of the earlier stages of
their development to be quite sure of their homology with
their undoubted analogues in the other Echinoderms.
Between the dorsal skeleton of the arms and pinnules and
the water-vessels on their ventral side, are three tubular
MINUTE ANATOMY OF THE BRACHIATE ECHINODERMS, 183
prolongationsof the body-cavity (figs.9—12). The middle one,
into which open the water-pores on the arms and pinnules,
is the genital canal already mentioned (figs. 9, 10, 12, 15,
g.¢.). The canals above and below it, which communicate
with one another at the end of each arm or pinnule, are
known respectively as the ventral or subtentacular (s. ¢. c.),
and the dorsal or ceeliac (c. ¢.). They are sometimes con-
nected in the pinnules by a series of lateral trunks, as seen
in fig. 12. In those Crinoids which have a central mouth
(Antedon, Pentacrinus), the subtentacular canals all arise
from a large central space in the axis of the visceral mass,
around which the digestive tube is coiled.’ In Actinometra,
however, which has an excentric mouth, the subtentacular
canals of the disc gradually become indistinguishable from
the general body-cavity, and there is no distinct axial
celom. Currents proceed through the subtentacular canals
to the tips of the arms and pinnules, and return to the disc
again by the celiac canals (3). These currents are due to
the action of cilia, which are not uniformly distributed, but
are localised in little cups on the top of each pinnule joint
that supports the lower part of the celiac canal (figs. 9, 11,
12 ct. c.). The genital and celiac canals are continuous
respectively with the ventral and dorsal portions of the cir-
cumvisceral division of the body-cavity, 7.e. the space
between what have been called the visceral and parietal
layers of the peritoneum (3,8). In September, 1875.
29.—Simroth, H., “ Anatomie und Schizogonie der Ophiactis virens, Sars,”
Theil i, ’: Zeitschr. f. wiss. Zool.,’ Band Xxvil, pp. 417—485, and pp.
555—560, Taf. xxxi—xxxv.
30.—Simroth, H., the same, Theil ii, ‘ Zeitschr. f. wiss. Zool.,’ Band xxviii,
pp. 419 —526, Taf, xxii—xxv.
31.—TZeuscher, R., “ Beitrage zur Anatomie der Echinodermen, i, Comatula
Mediterranea,” « Jenaische Zeitschr. f. Naturwissensch,’ ‘Band X, pp.
243—262, Taf. vii.
32.—Teuscher, R., “ Beitrage, &c., ii,",Ophiuride,” ‘ Jenaische Zeitschr.,’
Band x, pp. 263—280, Taf. viii.
33.——Teuscher, R., “ Beitrage, &e., iii, Asteride,” ‘Jenaische Zeitschr.,’
Band x, pp. 493—514, Taf, xvili and xix,
194 PROFESSOR E. RAY LANKESTER.
On Youne Sraces of Limnocopium and Geryonta. By
E. Ray Lanxester, M.A., F.R.S., Jodrell Professor of
Zoology in University College, London. With Plate
XIII.
METSCHNIKOFYS, in a paper in the ‘ Zeitsch. wiss. Zoologie,’
1874, p. 17, describes and figures the development of
Geryonia from the egg up to the formation of tentacles and
an umbrella cavity. It is, however, obvious from his figures
and description that certain steps in the development were
not followed by him with precision—and some of his ob-
servations are supplemented, whilst others are contradicted,
by those of Fol (‘ Jen. Zeitsch.,’ vol. vii). It appears to be
certain, from the observations of both Metschnikoff and Fol,
that in Geryonia the endoderm forms by delamination —
the embryo being, when it has so formed, a nearly spherical
“ diblastula”’ without orifice of any description (Metsch-
nikoff’s plate ii, fig. 7). The outer layer now grows away
from the inner, which remains in the form of a lenticular
sac, closely applied to one pole of the ectodermal sphere.
From this point forwards the accounts of Haeckel (‘ Jenaische
Zeitschrift,’ vol. ii), of Metschnikoff, and of Fol, are diverse.
A mouth is formed by a breaking through into the endoder-
mal sac, and a sub-umbrellar cavity is formed, and also a
velum and tentacles ; but the accounts given of the mode
of origin of these parts is not conclusive in any one of the
authors’ memoirs above cited. Haeckel observed Geryonia
embryos, in which he definitely states that the sub-umbrellar
cavity existed in the form of a closed sac. Metschnikoff
thinks this an erroneous observation, and due to a mistaking
of the endoderm sac for the sub-umbrellar cavity. According
to Metschnikoff, the ectoderm and endoderm are ruptured at
the central point where the enclosed endoderm sac is resting
on the inner wall of the larger ectodermal sac, and the
ectoderm is invagimated to form the sub-umbrellar cavity.
At the same time a ring grows up at some distance from the
mouth thus formed, which becomes the margin of the
umbrella, and gives off, on its adoral side, the velum; on its
aboral side, the first tentacles.
Fol’s account of the formation of the sub-umbrellar cavity
substantially differs from that of Metschnikoff in that he
does not derive the sub-umbrellar cavity from an invagination,
1 It is not possible to reject this well-established fact, as the brothers
Hertwig do, apparently without hesitation (‘ Coelomtheorie,’ 1881).
YOUNG STAGES OF LIMNOCODIUM AND GERYONIA, 195
but states that its walls form as an upgrowth around the
oral area, after the mouth has been formed by a rupture of
the ectoderm and endoderm at the centre of that area.
The observations which I have made upon young stages
of the freshwater Trachomedusa, Limnocodium Sowerbii,
lead me to think it probable that, after all, Haeckel’s
observations are correct, and that the sub-umbrellar cavity
is formed as a closed space between two layers of the ecto-
derm. It would not by any means be necessary to accept
the interpretation of appearances given by Haeckel to the
effect, viz. that the endodermal sac is the sub-umbrellar
cavity, but we have to suppose a step in development
intermediate between his fig. 28 and 29 (of Taf. iv, ‘Je-
naische Zeitschrift,’ vol. 11). In his fig. 28 the internal
sac which is drawn 7s the archenteron or endodermal sac.
In figs. 29 and 80 an ectodermal sac (formed, I would
suggest, by a hollowing out of the ectoderm, probably
without any opening to the exterior) has taken the place of
the primitive endodermal sac, which has become flattened
and otherwise modified to form the stomach and gastro-
vascular canal system (see Fol’s fig. 17, plate xxv, ‘Jen.
Zeits.,, vol. vii). The probability of the correctness of
Haeckel’s observations and inference as to the first ap-
pearance of the sub-umbrellar cavity as a closed sac, is not
only supported by my observations on Limnocodium, in
which this certainly is its condition at one period of its
development, but when we examine carefully the accounts
given by both Metschnikoff and Fol, we find that it is
precisely at the critical period which would enable them to
deal decisively with Haeckel’s observations that their series
of embryonic Geryoniz in both cases is deficient. Neither
Metschnikoff nor Fol have seen stages corresponding to
Haeckel’s figs. 29 and 30, with only four tentacles. They
both give series in which there is a sudden break at what
is the critical period for this matter; they pass at once from
the condition in which no tentacles are present to that in
which six are already manifest. (Fol’s figure 18 of an
embryo 82 hours old, with no tentacles, is succeeded by
figure 19 of an embryo, 156 hours old, with six tentacles ;
and Metschnikoff’s figure 10, which represents an embryo
about 50 hours old, having no tentacles, is followed by
figure 11, representing, as he states, an embryo 190 hours
old, and possessing six tentacles.)
It seems to me obvious from these facts that one of the
most important stages in the development of Geryonia is
still almost entirely unknown, and, accordingly, the stage
196 PROFESSOR E. RAY LANKESTER.
in the development of Limnocodium which I am about to
describe, corresponding as it does in a measure to the
missing stage in the Geryonia series, must not be judged
by reference to a scheme of Trachomedusan development
supposed to be already ascertained—for such a scheme does
not really exist upon any proper basis. Rather, it appears
the Limnocodium embryo may throw light on the im-
perfectly-known Geryonia development, and give credibility
to the important observations of Haeckel, which have been
too lightly dismissed by Fol and Metschnikoff.
I was only able to observe Limnocodium embryos of three
different ages, and those apparently very close to one another.
I have already figured two of those embryos (this Journal,
1880), and reproduce the woodcuts on the present occasion.
The third embryo is figured in Plate XIII.
Fie. 1.—Embryo of Limnocodium Sowerbii, 25th of an inch in diameter.
A. Surface view of oral pole. 2B. Optical section of same specimen
in a plane at right angles to the oro-apical axis. P¢. Per-radial ten-
tacle. JZ. Preumbral lid. RC. Radial canal. S¢. Stomach. Ze.
Ketoderm. G. Jelly of the disc.
The youngest stage observed by me is shown in the woodcut
fig. 1. At the tentacular pole is seen (a, L) a circular plate
of small cells absolutely imperforate and closing in the “ sub-
umbral cavity,” or “‘sub-umbrellar cavity ”—as is shown by
the optical section of the next stage, which is but a little more
advanced (fig. 28). This plate I call “ the preeumbral lid.”
It is surrounded by the rudiments of eight tentacles—four
of which (the per-radial tentacles) are somewhat larger
than the other four. In neither of these specimens are
YOUNG STAGES OF LIMNOCODIUM AND GERYONIA. 197
there any indications of the marginal bodies (tentaculocysts)
nor of avelum. Within the sub-umbral cavity—which is
capacious—we find the manubrium provided at its extremity
Fig. 2.—Embryo of Limnocodium Sowerbii, a very little more advanced,
A, Surface lateral view. &. Optical section of the same specimen in
a plane including the oro-apical axis. P¢. Per-radial tentacles. Z,
Preumbral lid. UC. Sub-umbrella cavity. Mz. Manubrium. RC.
Radial canal. #e. Ectoderm. G. Jelly-like substance of the disc:
with a mouth, which thus opens into the closed space of the
sub-umbrella. The cavity of the manubrium (stomach) can
be readily traced by optical sections and followed to the four
radial canals which run along the adumbral wall of the
umbrella—that which it is proper to call “‘ umbrella” being
the lateral wall of the sub-umbral cavity.
There is no indication at this stage of the sub-umbral
cavity having been formed by an invagination, the orifice. of
which has closed up; and although it, or its representative,
may thus form by invagination and become closed up in the
gonophores and modified Medusz of some Hydromeduse, |
see no reason to doubt that it has formed in Limnocodium,
as it does in Hydractinia, namely, by a splitting in the thick-
ened ectoderm (Ed. Van Beneden). The comparison of
the development of the directly developing Meduse with
that of the variously modified Medusz of hydroid colonies
will, I cannot doubt, furnish an explanation of the pheno-
mena which are observed in both series.
If we now pass to the later stage which is represented in
Pl. XIII, we find that although the young animal is but very
little larger in size, and has still. only eight tentacles, yet
certain changes of importance have occurred.
198 PROFESSOR E, RAY LANKESTER,.
In the first place, as seen in Pl. XIII, fig. 1, the pre-
umbral lid is now perforate, A minute opening has appeared
at its centre (0).
The preumbral lid does not, however, as might be ex-
pected, proceed to develop into the velum.! On the contrary,
the velum is already present as a distinct, highly muscular
fold, rising from the inner border of the ring which carries
the eight tentacles (Pl. XIII, fig. 1a). Its movements
are very active and constant, consisting in an alternation of
undulations of contraction and expansion—the latter move-
ment causing it to completely close in and hide the pre-
umbral lid, whilst its free margins come into contact centrally,
as seen in Pl. XIII, fig. 4. and fig. 5. In Pl. XIII, fig. 3, the
tentacular pole of the young Limnocodium is shown with
the velum completely expanded and its free margin brought
into such close contact at the centre of the tentacular area
that its existence is not at first suspected. Suddenly,
whilst this condition is under observation, the velum is seen
to roll back centrifugally and to expose the preumbral lid,
as shown in Pl. XIII, fig. 1.
It is necessary to state that there is no confusion here of
the true oral surface of the manubrium with the preumbral
lid. By causing the specimen to roll over, or by deeper
focussing, the manubrium, with its mouth, can be brought
into view lying at some distance below the perforated pre-
umbral lid within the sub-umbral cavity—just as it was
seen in the earlier stage (woodcut, fig. 2B).
Besides the velum and the perforation in the preeumbral
lid, the tentaculocysts (marginal bodies) have now com-
menced to develop. Two are present—one a little more
advanced in development than the other—and are seen in
Pl. XIII, figs. 1 and 2, o¢., and in fig. 6. An endodermal
axis and an ectodermal cortex are present, but the secondary
investing capsule, or velar canal, is not yet indicated.
Besides the movements of the velum there are very active
and sudden movements of the whole umbrella, and also
slower movements of contraction and expansion, which
give to the embryo the irregular outline depicted in the
plate. At the stage now under description, striated mus-
cular fibres can be detected in the wall of the umbrella
(Pl. XIII, fig. 2 ee). The radial canals are large and give
evidence of ciliation of their lining cells.
1 The distinction between preumbral lid and velum—which develops
later than the lid itself and from its periphery—is borne out by Metschni-
koff’s observations on Geryonia,
YOUNG STAGES OF LIMNOCODIUM AND GERYONIA, 199
scheme of development of Geryonia and Limnocodium.—
Such being the facts with regard to a limited period of the
developmental history of Limnocodium, they can, I think,
best be brought into harmony with the observations of
Haeckel, Metschnikoff, and Fol on Geryonia by introducing
between the earlier and later stages described by the two
latter observers a hypothetical stage, as exhibited in the
woodcuts, figs. 3, 4,5. Fig. 5 is simply a schematic re-
presentation of the stage (three days and a half) drawn by
Fol in his plate xxv, fig. 18, and shows the thickened
ectoderm, which he calls “ the oral plate,” but which I
shall call “the umbrella plate.” Fig. 5 is a schematic
section of an eight or ten days’ embryo based upon Metsch-
nikoff’s fig. 14 (pl. 1, ‘ Zeitsch. wiss. Zool.,’ vol. xxiv).
Metschnikoff believes that the sub-umbral cavity is formed
by an invagination, which at the same time gives rise to the
oral aperture. His drawings, which are by no means
decisive, appear to admit of the interpretation of a formation
of this cavity by the splitting of the umbrella plate: especially
I would refer to his fig. 11, where the enteric sac and the
sub-umbral space are seen as two lenticular bodies closely
applied to one another. In any case I have no doubt that
Metschnikoff’s figures are far more nearly representative of
the process which goes on in the formation of the sub-umbral
space in Geryonia than are Fol’s; and the account of the
process which he has based upon his observations, though,
as 1 think, erroneous (owing to the absence of observations
on embryos between the 50th and the 190th hour), are yet
by no means so wide of the truth as those of Fol, who has
completely failed to give even an approximately correct
account of the matter.
We may now interpose between the stages represented
by figs. 3 and 5 a hypothetical representation of the stage
not observed by Metschnikoff or Fol, basing our suggestion
upon the fact observed with regard to the young Limno-
codium, namely—that the sub-umbral cavity is large and
well developed at a stage when it has no opening to the
exterior, but is completely closed in by an imperforate pre-
umbral lid.. Such a stage is represented in the woodcut, fig. 4.
There is little room for doubting that the series 3, 4, 5 is true
for Limnocodium, and that 5 and 6 are true for Geryonia.
It will not be a difficult task to decide by the special
examination of Geryonia embryos whether the aperture in
the preumbral lid seen in stage 5 forms after the sub-
umbral cavity and the oral perforation of the manubrium
are complete, as it does in Limnocodium, or whether, as
200 PROFESSOR E, RAY LANKESTER,
Metschnikoff supposed (but did not demonstrate) the aperture
in the preeumbral lid is an orifice of invagination, by which
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the sub-umbral cavity and the perforation of the manubrium
have been brought about. In the latter case an important
but readily intelligible difference between Limnocodium and
Geryonia would be established.
YOUNG STAGES OF LYMNOCODIUM AND GERYONIA, 201
Relation to the morphology of Ctenophora and of Medusoid
Gonophors.—I have already alluded to the reciprocal illustra-
tion afforded by the development of the sub-umbral cavity
in such gonophors as those of Hydractinia, and in meduse
developing directly from the egg.
The exceedingly important and (as I think) convincing
reference of the Ctenophora to the Hydromedusa type, made
by Haeckel (‘ Sitzungsber. der Jenaichen Gesells.,’ 1879,
p- 70), is in no small degree rendered acceptable by the
existence of directly-developing Meduse in which the sub-
umbral space has the form of a closed chamber, or of a
sac with but a narrow opening to the exterior. This
sub-umbral sac appears to correspond with the so-called
stomach of the Ctenophora, and its opening with the so-
called mouth of those forms. In both cases it is lined by
ectoderm, and develops quite independently of the endoder-
mal cells, which give rise to the stomach and canals of the
Hydromedusze on the one hand, and to the infundibulum
and canals of the Ctenophora on the other hand.
Balfour (‘ Embryology,’ vol. i, p. 145) compares the ecto-
dermally-originating ‘‘ stomach ” of Ctenophora to a stomo-
dzeum,' and more especially to the stomodeeum of Acraspedote
Meduse (Scyphomeduse) and Anthozoa.
But if this assimilation be well founded, the stomodeum
of Scyphomedusze and of Anthozoa will be morphological
equivalents of the sub-umbral space (sub-umbrellar cavity)
of Hydromeduse ; and the question presents itself as to
whether the stomodeum of the higher groups—with its
wide dimensions and contractile walls—may not be similarly
identified. Against such a view there appears to be a
strong argument in the very general presence in higher
animals of a “ proctodzeum ”—an anal ectodermal invagina-
tion, parallel in its origin to that connected with the mouth.
It may, however, be worth while to examine the facts of
morphology in reference to this suggestion.
1 The name applied by me and adopted by Balfour for the ectodermal
invagination which gives origin to the mouth and first portion of the ali-
mentary tract in all Metazoa except some Ceelentera. See this Journal,
October, 1876.
VOL, XXI,—NEW SER. )
202 EDMUND B. WILSON.
The Or1GIn and S1GNIFICANCE of the METAMORPHOSIS of
ActinotrocHa. By Epmunp B. Witson, Fellow in
Biology, Johns Hopkins University. With Plates XIV,
4 e
Axouvt thirty-five years ago Johannes Muller described a
very curious free-swimming pelagic animal which he cap-
tured at the surface of the sea at Heligoland, in the North
Sea, giving to it the name Actenotrocha, in allusion to its
beautiful circlet of ciliated swimming arms. The striking
appearance, and very peculiar structure of this creature sub-
sequently attracted the attention of many observers. Wagener
described its anatomy, supposing it to be an adult animal
Krohn subsequently discovered, however, that Actinotrocha
passes by a sudden metamorphosis into a Gephyrean worm ;
and some years later Schneider made out the true nature of
this very remarkable process. The life-history was at length
completed by Kowalevsky, who, by raising the eggs, proved
that the adult worm is the singular Gephyrean Phoronis,
which had long been of especial interest as forming a sup-
posed transition from the Polyzoa to the Annelides. The
matter was then carefully revised by Metschnikoff, who
studied another species found in the Mediterranean Sea, and
published in 1871 a valuable paper setting forth the results
of his observations.
No attempts were made in these papers to offer any ex-
planation of the origin and significance of the singular
change undergone by the larva in its passage to the adult
form. I was thus led, during the summer of 1879, while
enjoying the facilities afforded at the Chesapeake Zoological
Laboratory, to undertake a renewed study of the subject
with two species of Actinotrocha commonly occurring in
Chesapeake Bay. As a result of this study, an hypothesis
has suggested itself that seems to me to afford a reasonable
explanation of the steps by which the adult structure and
strange metamorphosis of Phoronis may have been acquired.
Moreover, a study of this particular case places in a very
clear light some of the phenomena of metamorphosis in
general, and is conducive to an understanding of the causes
which have led to certain remarkable methods of develop-
ment in a number of animal groups. In many cases of
metamorphosis the phenomena of growth are so complex
that it is extremely difficult to form any definite conception
of the exact way in which they have been brought about.
METAMORPHOSIS OF ACTINOTROCHA, 2038
In the development of Actinotrocha, however, we find a
metamorphosis involving profound and remarkable changes
of structure, and yet produced by very simple processes of
growth. The problem to be solved is much simplified and
comparatively definite—reduced as it were to its lowest
terms. While the contrast between the structure and
habits of the larva and those of the adult is so striking as
to show very clearly the general causes which have brought
about the metamorphosis, it is possible, I believe, to get
some idea of the exact way in which these causes may have
operated in producing the peculiar transformation which the
creature undergoes.
In order to render these considerations intelligible, it will
be necessary to give some description of the metamorphosis.
The first part of this paper is therefore devoted to such a
description, based upon my own observations and those of
Metschnikoff. Although the account of the Russian em-
bryologist is very complete and satisfactory, my own obser-
vations are not without some value as supplying many
hitherto unobserved details of the process, and from having
been made upon two distinct species, neither of which can
be satisfactorily identified with that studied by Metschnikoff.
Certain discrepancies will be noted further on. I succeeded,
moreover, in keeping the young Phoronis alive during several
weeks—until they had, in fact, assumed the characteristic
appearance of the full-grown animal. For the sake of com-
pleteness, a few of Metschnikoff’s figures of the earlier stages
have been introduced (figs. 1, 4.).
Part I.
It may be convenient to preface the following descrip-
tion, with a short summary of the more important points.
The larva has a somewhat elongated body with a series of
long ciliated arms nearly encircling the body behind the
mouth, and a narrow belt of long cilia just anterior to the
anus, which is situated at the posterior end of the body.
The mouth is on the ventral side near the anterior end, and
is overarched by a very large hood-like expansion of the
body wall, the preoral lobe. The hood is richly ciliated
and serves to produce currents of water flowing towards the
mouth, which bring with them particles of food.
The only internal organ at first is the digestive canal,
consisting of a distinct esophagus, a capacious stomach,
and a longer or shorter intestine. In time, however, the
ventral wall of the body thickens at a point in the middle
204 EDMUND B, WILSON,
line just behind the circlet of the arms. This thickening
is apparently produced by an infolding of the body wall;
at any rate, it soon becomes hollow and pouch-like, and
communicates with the exterior by means of a small opening,
while fibrous or muscular connections between it and the
stomach walls may be observed. The pouch grows rapidly,
and at length comes to occupy a large part of the peri-
visceral cavity, doubling back and forth, and becoming
transversely folded on its inner wall.
When the pouch has attained its complete development
the larva becomes sluggish, sinks to the bottom, and the
body usually contracts forcibly, so that it becomes shortened
and rounded, and the walls become tense from the internal
pressure thus produced. Suddenly, at what Metschnikoff
appropriately terms the “critical stage” of the metamor-
phosis, the pouch turns itself outward through its external
opening, unrolling like the finger of a glove or the eye ten-
tacle of a snail. As it unrolls, the middle part of the diges-
tive canal is drawn out into its cavity, thus forming a long
U-shaped loop. At the same time the larval body shrinks
together, and is doubled up toward the dorsal side, so that
the mouth and anus are brought close together. The hood
is withdrawn into the esophagus, leaving only a small rem-
nant, which overhangs the mouth and persists as an epis-
tome. The greater part of each swimming arm undergoes a
kind of granular disintegration and drops off, leaving only a
small thickened basal portion, which becomes directed for-
wards, and subsequently grows into the corresponding ten-
tacle of the adult Phoronis. The larval body fuses com-
pletely with the everted pouch, which now constitutes the
greater part of the body of the worm. The subsequent
external changes consist merely in the elongation of the
tentacles and a great increase in their number, and the
elongation of the body. The worm secretes for itself a
membranous tube, in which it dwells, protruding only the
extremity with its crown of tentacles. The resemblance of
the latter to the lophophore of a hippocrepian Polyzo6n is
wonderfully close, though this resemblance is undoubtedly
adaptive and secondary. A clear idea of the metamorphosis
may be gained from the diagrammatic figs. 15 to 19.
Figure 1 represents a lateral view of the first stage figured
by Metschnikoff. Ath. is the hood; m.is the mouth lead-
ing by a short cesophagus to the stomach (s¢.). The latter
communicates by a short intestine with the anus (a). Rudi-
ments of two swimming arms are seen at a’, a.” Fig. 2
gives a ventral view of the same; rudiments of the second
METAMORPHOSIS OF ACTINOTROCHA. 205
pair of arms are seen at a”, a’, Fig. 3 is a corresponding
view of a somewhat later stage with the first four arms now
plainly indicated. The body is everywhere richly ciliated
and the cilia are distinctly longer along the margin of the
hood and at the tips of the arms. Fig. 4 represents a side
view of a considerably later stage, with five pairs of well-
developed, though still short, arms. A number of large
black pigment spots have appeared. Neither the pre-anal
belt of cilia, nor the ventral pouch, have yet been developed.
These four figures are copied from Metschnikoff.
The following figures represent different stages in the
development of the two Chesapeake species, which for con-
venience sake may be designated A and B. The two
species have well-marked specific differences, but their me-
tamorphoses are almost identical, and agree in the main
with that of the form studied by Metschnikoff. A is cha-
racterised by a very short intestine and a correspondingly
stout body, and shows a considerable resemblance to the
form studied by Metschnikoff (figs. 5, 7,11). B has a long
slender intestine, and the posterior part of the body is cor-
respondingly elongated. At the upper lateral portions of the
stomach are two rounded glandular lobes, one on either side
of the esophagus. The hood, in the later stages at any rate,
has a prominent conical ciliated elevation on the median
line in front. This form is apparently identical with Ac#i-
notrocha branchiata, the species originally discovered by
Johannes Miller.
Figure 5 represents form A shortly after the appearance of
the pouch which is seen in optical section at p on the
ventral side. The arms are sixteen in number; they di-
minish regularly in length toward the dorsal side, thus
indicating the order in which they have appeared. On the
extreme dorsal side the series is interrupted by a consider-
able interval. The arms are nearly solid, but contain
narrow central channels, which are diverticula from the
perivisceral cavity. There are a number of pigment spots
irregularly scattered over the body. The pre-anal belt of
cilia (a. r.) has appeared, the dorsal vessel is seen at v., and
. an accumulation of pseud-hzemal corpuscles has appeared
at cor. on the wall of the stomach. By flattening out the
creature under a compressor the opening into the pouch
becomes apparent (fig. 7).
Figure 6 represents the corresponding stage of the other
species as seen from the opposite side, showing the pouch
(p.) lying in the perivisceral cavity between the stomach and
the body wall, It shows the ventral pseud-hemal vessel
206 EDMUND B, WILSON.
with rudinients of the contractile czeca (c.), which are so
striking a peculiarity of the adult circulatory apparatus.
Figure 8 represents a considerably later stage, in which is
shown a great advance in the development of the pouch.
Bending at first toward one side of the body it folds upon
itself, and returns to the opposite side, then turns sharply
downward along the intestine, and finally bends upward
again near its extremity. Its inner walls are transversely
folded. ‘The arms have increased to the number of twenty,
and are thickened on the lower side just at the base, to form
the first rudiments of the permanent tentacles. There are
four masses of pseud-hemal corpuscles, two lying at each
side of the stomach.
Figure 9 gives a dorsal view of the same stage, to show
the arrangement of the arms on the dorsal side. The folds
of the pouch have here a somewhat different arrangement,
and cannot be clearly followed. The rudiments of the ten-
tacles are shown at p.a., and the broad contractile dorsal
vessel at v.
Figure 10 represents a full-grown larva of B immediately
before its metamorphosis. The folds of the pouch are
voluminous, and occupy a large part of the perivisceral
cavity ; they have nearly the same disposition as in fig. 8.
The tentacular rudiments are very distinct, and have become
partly independent of the larval arms. Both dorsal and
ventral pseud-hzmal vessels are well developed and, like the
ceecal appendages, are actively contractile. The masses of
corpuscles (cor.) are large and very conspicuous from their
red colour. Form A agrees essentially with B at this stage,
though the body is much stouter, and the rudiments of the
tentacles are much smaller and more closely united to the
larval arms.
The two species differ slightly as to the manner in which
the metamorphosis is effected. In the case of A the larva
sinks to the bottom, contracts very strongly, and the evagi-
nation of the pouch occupies but a few minutes. The pro-
cess occupies in the case of B a much longer time, and the
body is only slightly or, at first, not at all contracted.
Figure 11 represents the latter species at the erdtical
stage, with the pouch about half unrolled. The inner ex- .
tremity of the latter still extends to the back of the stomach.
At 6,6, are seen some of the fibrous connections between the
intestinal walls and those of the pouch. ;
Figure 12 represents the creature with the pouch (the
whole of which is not shown) wholly unrolled. The hood
has been withdrawn into the cesophagus, the larval arms
METAMORPHOSIS OF ACTINOTROCHA. 207
have dropped off, and the short tentacles are directed straight
forwards, and form a circlet surrounding the mouth. The
posterior portion of the larval body (p.), with the anus at
its extremity (q.), is still distinct, and is bent at right angles
to the long axis of the pouch, which must now be called the
body proper. In time it becomes bent still further upwards,
and, at the same time, is gradually withdrawn into and fuses
with the remainder of the body. Ultimately it quite dis-
appears, and the anus remains as an opening on the side of
the body, immediately behind the circlet of tentacles.
Figure 13 represents 4 about twenty-four hours after the
metamorphosis, when the larval body has completely fused
with that of theadult. The body is soft and extensible, and,
though it has numerous transverse folds when contracted,
there is no indication of metamerism. The aboral extremity
is extremely changeable in shape; two forms commonly
assumed are shown. The surface is everywhere finely
granular, and becomes distinctly tuberculose towards the
aboral extremity.
New tentacles are henceforward constantly budded forth
at the dorsal side of the lophophore, at about the rate of a
new pair every day, until their number becomes a hundred
or more, and they increase gradually in length.
Figure 14 represents the same individual as that shown
in fig. 13 twenty-two days after metamorphosis, and practi-
cally in the adult condition. The tentacles are richly
ciliated, and have exactly the same appearance and perform
the same movements asin the Polyzoa. Each has, however,
a cecal vessel from the pseud-hemal circumoral ring, and
performs a distinctly respiratory function. The pseud-hemal
fluid is very remarkable from the presence of numerous
large, oval, nucleated corpuscles, which look not very unlike
the red corpuscles of frogs’ blood, though of less regular
shape. They are also red in colour, and render all the
branches of the pseud-hemal system very conspicuous, so
that their arrangement may be very easily made out. In
neither of the Chesapeake species is there a vessel run-
ning along the intestine towards the anus, although such a
vessel is figured by Metschnikoff. Norcan I agree with this
observer that the corpuscles of the pseud-hzemal fluid are
developed free in the perivisceral cavity to be drawn into the
pseud-hemal vessels at the time of metamorphosis. There
cannot be the least doubt that in both our species these cor-
puscles are developed in solid masses adhering to the
stomach walls, near the base of the tentacles, and I believe
them to a rise within the cavity of a sinus, which becomes
208 EDMUND B. WILSON.
the circumoral ring of the adult. They never float freely
in the perivisceral cavity, and cannot for a moment be con-
founded with the true blood-corpuscles of this cavity. During
the metamorphosis these masses suddenly break up, and the
corpuscles are almost immediately carried along within the
vessels by the peristaltic contractions of the latter. During
the later larval stages they are sometimes elongated towards
each other, and connected by a narrow band containing a
few corpuscles (see fig. 10) ; and repeated observations of the
metamorphosis has convinced me that, for our species at
least, Metschnikoff’s account is incorrect. Owing to the
failure of attempts to make satisfactory sections of the larvee
I have been unable absolutely to demonstrate this point,
which is of considerable importance from its bearings on
the relation between the pseud-hemal system and the body
cavity.
Part II.
Before advancing speculations as to the origin and sig-
nificance of this most remarkable course of development, it
is necessary to dwell for a mcment on the systematic rela-
tions of Phoronis, and on certain structural features of the
group to which it belongs. It is pretty well agreed that
Phoronis is a Gephyrean, although a greatly modified and
specialised representative of this peculiar group. Although
the peculiarities of its development are so great as to lead
so high an authority as Mr. Balfour to question the cor-
rectness of this identification, I believe, nevertheless, that
these doubts are not well-founded. In all essential ana-
tomical characters, so far as they are known, Phoronis agrees
closely with such forms as Sipunculus or Phascolosoma. Its
most striking characters, such, for example, as the close prox-
imity of the mouth and anus and the high development of
the oral tentacles, are simply exaggerations of characters
possessed by the last-named genera. Almost all of the adult
characters are readily explicable as the result of extreme
adaptation to a strictly tubicolous life. In regard to the
development, I shall endeavour to show that its peculiarities
are almost certainly due to secondary adaptations, correlated
with the highly specialised structure of the adult. Many
facts show that it is not worth while to attach much import-
ance to soinconstant and variablea character as the arrange-
ment of ciliated belts in pelagic larve. But if this point
were of importance, their arrangement in “ Beitrage zur Kenntniss der Monaden,” ‘ Archiy fiir mikrosk. Ana-
tomie,’ Bd. I, 1865, S. 203.
238 D. D. CUNNINGHAM.
nourished at the expense of an active amcboid organism, it
becomes adherent to it by its posterior extremity. The Ameba
at first continues to progress freely, but soon ceases to do so,
assumes a spherical and motionless condition, and is dragged
passively about by the energetic flagellary movements of the
zoospore. Gradually a diminution in its bulk becomes manifest,
the body of the zoospore at the same time becoming distinctly
plumper and more refractive, and as the process continues the
whole, or almost the whole, of the Amceba disappears, and its
plunderer swims off to seek a new victim. Sometimes several
zoospores unite in plundering one Ameeba, which is jerked irregu-
larly about by their opposed movements. In the case where
red blood-corpuscles are the source of nutriment, as is fre-
quently the case in choleraic evacuations, the progress of the
process may be followed readily by the colouring of the zoospore-
body by the absorbed hemoglobin. In some cases portions of
corpuscles, too, seem to be absorbed ex masse, though it is
difficult to be quite certain on this point, due to appearances
arising from surface adhesion to the transparent bodies of the
zoospores.
Owing to the constant movements presented by the parasites
when in full activity, it is difficult to come to any definite con-
clusion regarding the frequency with which they possesss a
differentiated nucleus or contractile vesicle. That they do do soin
some cases there can be no doubt, but in many the most careful
and prolonged examinations fail to reveal the presence of either
structure. That the presence or absence of a distinct contractile
vesicle is not a matter of essential specific importance, is the
conclusion which Hertwig and Lesser seem to arrive at as the
result of their study of the Rhizopoda,! and the phenomena
presented by the organisms at present under consideration cer-
- tainly corroborate thisconclusion. The presence of a contractile
vesicle appears to be an inconstant character, determined, in
some cases at all events, by conditions of the nutritive medium.
With regard tothe constancy of a nucleus as a specific cha-
racter, it is necessary to speak with some reserve, as the presence
of such a structure may readily escape observation in such
minute organisms as the excretal zoospores. This is more
especially likely to occur where a distinct nucleolus is not
present and where the nucleus is merely represented by a clear
vacuolar area in the body-mass. That these conditions may
replace one another in one and the same organism is, as we shall
see hereafter, unquestionable, bodies which at one period merely
show a clearer nuclear area subsequently showing a conspicuous
1 “Ueber Rhizopoden und denselben nahestehende Organismen,” ‘ Ar-
chiv fir mikr, Anat.,’ Bd. X. Suppl.
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 239
nucleolus within this. In certain cases, as Dr. Lewis pointed
out in 1870, the excretal zoospores do show clear areas which
are probably of a nuclear nature, and in others either previous
to or after treatment with reagents, and specially with Liquor
Todi, a nucleoloid particle is rendered manifest. Without feel-
ing justified in stating it as a positive fact, 1 am strongly in-
clined to regard the presence or absence of a nucleus as con-
nected in the present case rather with developmental than
specific character. The body of the parasite varies consider-
ably in appearance in different cases, and at different times in
one and the same specimen, being sometimes almost homogeneous
and in others distinctly granular.
After continuing in full activity for some time, the zoospores
sometimes pass into a condition in which they exhibit very free
ameeboid changes of form, accompanied by frequent retraction
and protrusion of flagella. Frequently connected with this stage,
but sometimes also occurring as a mere interlude in the condition
of maximum activity, processes of multiplication by division
take place. Division is preceded by a temporary cessation of
activity, the flagella being retracted and the body assuming a
more or less spherical form (Plate XVIII, fig. 17 4). The out-
line soon become oval, a constriction now appears transverse to
the long axis of the body and rapidly deepens, and a new flagel-
lum appears at either pole and begins to act with energy (Plate
XVIII, fig. 17, 4,2). The central contraction continues to in-
crease in depth, and ultimately the two segments remain con-
nected merely by a narrow neck, which, due to their energetic
struggles, is soon reduced to a thread (Plate XVIII, fig. 17, 7),
and finally gives way, so as to allow the two twin zoospores to
part company and swim off freely in the medium.
In other cases a retardation of movement is the antecedent to
the death of the zoospores, as may frequently be observed
when unfavorable alterations are naturally or artificially taking
place in the medium. It is in these cases that they come to
present features causing them to agree with Stein’s description
of those in Trichomonas. The movement ceases to be one of
energetic rotatory advance and assumes a jerking character.
This jerking is due to the emission of lateral pseudopodial pro-
trusions in rapid succession. Where the emission, as is fre-
quently the case at first, is very rapid, an appearance arises as
though the body possessed a lateral row of cilia. As, however,
a gradual retardation sets in, the true nature of the phenomenon
ean be readily determined. It is now seen that distinct, slender
pseudopodial processes, often of considerable length, are emitted
from the side of the body, and sweeping round in a curve are
again retracted. Sometimes two are visible at once, a fresh one
240 D. D. CUNNINGHAM,
beginning to be emitted ere the entire disappearance of its pre-
decessor. ‘he pseudopodia gradually diminish in size as time
goes on and finally disappear, the last traces of their formation
being represented by mere wave-like undulations of the body-
margin. The flagella have been retracted some time previously,
and the zoospore finally remains as a mere rounded or oval par-
ticle of protoplasm, which rapidly breaks down into a molecular
flake and disappears.
The presence of zoospores is by no means confined to cho-
leraic excreta. They certainly, as a rule, are present in such
excreta in much larger amount and much greater activity than
in other cases, but in many cases of intestinal disease of other
nature they may readily be detected, and even in cases where no
abnormal condition exists, they are very frequently present in
small numbers. Although this is the case, they may readily
escape observation, and this for several reasons. In the first
place, they are frequently inactive ; and secondly, even where
they are not so, the nature of the medium is such as to prevent
their free movement. Moreover, they are so easily and prejudi-
cially affected by changes in the medium, that the means
employed to facilitate their detection very often defeat their own
end. ‘Thus, the addition of water is in almost all cases enough
almost immediately to secure the abolition of motion, and very
rapidly to lead to disintegration and disappearance of the zoo-
spores. The two media which I have found most adapted to
secure the demonstration of their presence are, first, the alkaline
fluid of choleraic excreta; and second, a solution of cow dung.
In either case, before using the media, it is of course necessary
to filter and boil them in order to exclude débris and organisms
which they may contain. In my first observations I always
employed the choleraic fluid, but latterly I have entirely aban-
doned this in favour of the solution of cow dung, which seems
to be peculiarly favorable to the zoospores.
The presence of the zoospores in the excreta is then a pheno-
menon not peculiar to cholera, or indeed to any diseased con-
dition. On the other hand, certain diseased conditions of the
excreta appear certainly to be incompatible with their presence.
As I previously pointed out,! cases of acid diarrhoea associated
with the presence of growing fungal elements are characterised
by the absence of any traces of the zoospores. This in itself is
sufficient to show that mere fluidity of the medium is not the
only condition necessary for the occurrence of these organisms.
That this is the case is also proved by their entire absence in
many cases of dysentery. A much more important determinant
1 Appendix B, ‘Seventh Annual Report of the Sanitary Commissioner
with the Government of India,’ Calcutta, 1871.
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 241
seems to lie in the reaction of the medium, an acid reaction
repressing, and an alkaline one favouring, their presence and
development. At the same time, however, certain forms of
alkalinity, associated with the excessive development of other
organic forms, are almost as repressive as acidity ; but, as a rule,
there can be no doubt that alkalinity of the medium is one of
the necessary conditions for their presence in any considerable
numbers, and that any excessive acidity is most destructive to
them.
This alone is sufficient to account for the extent to which
their presence in the excreta in health has escaped notice. In
health the excreta, as a rule, present a faintly acid reaction when
perfectly fresh, but the degree of acidity mcreases so rapidly
that within a short time the medium becomes quite unadapted
to the requirements of the zoospores, which consequently die
and disappear. Even where the materials, when fresh, are
neutral, or, as is sometimes the case, exhibit a mixed reaction
with alkalinity more permanent than acidity, the rapidity of the
development of an intensely acid condition is very great, so that,
unless examined at once, they may show no traces of zoospores.
There is also another circumstance which must be regarded as
probably accounting in part for the rarity with which these
organisms have been detected in Europe, uamely, that a depres-
sion in the temperature of the medium, as is the case with many
other organisms, exerts a most rapid and prejudicial effect on
them. During the hot weather months in India this influence
exerts hardly any appreciable effect, but in the cold season it
comes into play more or less distinctly.
While considering the subject of the influence of the condi-
tion of the medium on the vitality of the zoospores, it may be
well to examine a little more closely the phenomena attendant
on the decomposition of normal alvine excreta in this country.
These phenomena exhibit a wonderful uniformity, as shown by
the records of very numerous observations conducted at all
times of the year, and at intervals of several years’ duration.
When exposed to rapid drying, comparatively little change
beyond increased acidity has time to take place. When, on the
other hand, the materials retain their moisture, as, for example,
when they are reserved in an isolated moist chamber, a definite
series of phenomena manifest itself with great regularity. The
first change appreciable consists, as before said, in a very rapid
increase in acidity, so that the material, after the lapse of twenty-
four hours, shows an intense and permanent acid reaction.
This condition is associated with a change in the colour of the
basis, specially when exposed to the air, a darkening and red-
dening being more or less distinctly manifested. At the close
242 D. D. CUNNINGHAM.
of forty-eight hours the material is intensely and permanently
acid. If the surface be examined closely at this stage, it will
almost invariably be found to be covered with numerous short,
erect hyaline points, which on microscopic examination are
resolved into filaments of Ozdium lactis, beginning to break up
into conidial segments, and arising from a series of elongated
horizontal tubes traversing the superficial portion of the basis
(Fig. 1). Twenty-four hours later the surface is universally
covered with a thick shaggy grey coating consisting of dense
masses of conidia.
Fic. 1.—Filaments and cells of Oidium x 1000.
The following are the notes recorded in reference to these
phenomena in one case, which may be taken as typical of the
normal course under similar conditions. A portion of perfectly
fresh normal alvine excreta was placed in a carefully cleaned
capsule in a moist chamber at 12 noon. ‘The reaction of the
material was distinctly acid. Microscopically, it consisted of
the usual elements. Twenty-four hours later it had acquired a
reddish tinge, and the acidity was greatly increased. After
another interval of twenty-four hours it was covered by a deli-
cate whitish bloom, due to the presence of myriads of short,
erect, projecting fungal filaments, which on microscopic ex-
amination were found to present the characteristic features of
young conidial filaments of Ocdiwm lactis. The reaction was
now violently acid. The average breadth of the fungal elements
was 5 wu. Many of the filaments were of considerable length,
and showed no traces of division; while in others, all stages of
that process were clearly manifested, and numerous free conidia
represented results of its completion. After separation the
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 243
conidia seem, as a rule, to become broader, and their extremities,
which are at first in many cases more or less truncate, assume a
rounded convex outline. In some cases the filaments appear to
divide dichotomously at the extremity. The superficial layers
at the basis were full of long, horizontal, sparsely-branched
filaments, from which short vertical twigs arose, became aerial,
and ultimately split up into conidial segments. After another
interval of twenty-four hours the reaction of the basis was
transiently but distinctly alkaline, and the surface was clothed
with a thick, shaggy, greyish-yellow coating of curious gela-
tinous, acutely conical tufts, composed of dense masses of oidial
conidia and filaments. Most of the conidia were very short
and broad, many being nearly spherical. They were full of
dense shining protoplasm, only showing at utmost one or two
minute vacuolar spaces. On being sown on a suitable medium,
they rapidly germinated, undergoing a great increase in size,
accompanied by extensive vacuolation ere doing so. The short
rounded conidia measured from 9°4 x 6*ly to 6°5 x 6:0 or
55 uw. The longer joints measured 23 x 5°5 yu, and all inter-
mediate forms connected the two series with one another. On
the following day the reaction of the basis was distinctly aud
permanently alkaline, and no farther development of fungi
occurred in it.
That the Oidium in this and other cases owed its origin to
fungal elements intrinsic to the basis, and not to extrinsic ones
accidentally introduced from without, was proved by the follow-
ing facts :—1st. Ocdiwm lactis is not a form which tended other-
wise to occur spontaneously in any of the localities in which the
experiments were conducted. 2ud. Boiling the excreta previous
to isolation was invariably followed by a failure in the appear-
ance of the fungus, and this not as the result of any change
causing them to become an unsuitable medium for it, as an
abundant crop appeared as usual on introducing oidial elements
artificially. It cannot, moreover, be assumed that in the experi-
ments on the effect of boiling, the excreta were originally fortuit-
ously an unsuitable medium, as check experiments were tried
with unboiled portions of the same material, which constantly
resulted in the occurrence of the normal development. That the
phenomenon is not one dependent on casual peculiarities of a
particular season was shown by its uniformity at intervals of
several years’ duration. Besides the experiments on a large
scale in ordinary moist chambers, others were tried in which
minute fragments of the material were hermetically sealed in
wax cells, and the sequence of events in these cases was pre-
cisely of a similar nature. There can, I think, be little doubt
that the digestive canal in man in this country normally contains
244 D. D. CUNNINGHAM.
the reproductive elements of Oidium /actis, just as that of the
cow normally contains those of Pi/obolus erystallinus and other
stercoreous fungi.
The development of the Oidium is, as we have seen, coinci-
dent with a great increase in the acidity of the basis, and the
question naturally suggests itself, how far the two phenomena
are causally connected, and how far the increased acidity is due
to a fermentive action dependent on the growth of the fungal
elements. That it is partially—but only partially—dependent
on this appears to be clear from the’ result of a series of experi-
ments in which neither Oidium nor any other mould-fungus was
developed, and in which, at the same time, a distinct but tem-
porary increase in acidity sometimes manifested itself. The
notes recorded regarding one of these cases are as follows :—A
portion of fresh acid alvine excretion was boiled and set in a moist
chamber. Twenty-four hours later there was a distinct increase in
the degree of acidity. On the following day it exhibited a mixed
reaction, being faintly and transiently acid when first applied to
the test paper, and the acidity passing off and being replaced
by permanent alkalinity on drying. On the next day all trace
of acidity had disappeared, and a permanent and distinctly
alkaline condition was present. In other cases, however, and
these constituted a great majority, the reaction at the close of
twenty-four hours either remained unaltered, or indicated an
increase in alkalinity, and after forty-eight hours’ reservation an
alkaline condition was almost invariably strongly pronounced.
The increase in acidity never approached in degree that asso-
ciated with the development of Oidium, and the phenomenon,
where present, may, I believe, be regarded rather as an evidence
of diminished manufacture of alkaline products than of any
positive increase in acid-formation. The reasons for this belief
are the following :—The appearance of alkalinity in the materials,
whether boiled or unboiled, is associated with an enormous
development of bacterial elements. During the stage of acidity
normally coinciding with the development of Oidium, bacterial
development seems to be suppressed or very greatly retarded,
and it is only when the fungal development ceases that it comes
actively into play. Prolonged boiling also causes an immediate
suppression of bacterial development for the time, and at the
same time permanently suppresses the oidial elements. If, then,
any volatile acid or alkaline elements are originally present, a
development of either acid or alkali may seem to occur, due really
to alterations in the relative proportions of the products incident
on the escape of volatile compounds and not on any increased
formation.
As noted above, while the suppression of fungal elements by
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 245
boiling is complete and permanent, an abundant development of
bacteria almost invariably afterwards occurs, even in cases where
the greatest precautions are taken to secure the exclusion of ex-
trinsic elements. The following notes were recorded of the phe-
nomena in one case of this kind :—A portion of normal excreta
Fic. 2.—Excretal Bacilli x 1000.
was boiled for half an hour, and set whilst boiling in a moist
chamber. This remained closed for forty-eight hours, and the
specimen was then examined. ‘The reaction was alkaline, and
the surface of the medium was found to swarm with minute
active bacilli (Fig. 2). On the following day the majority of the
bacilli had passed into the still condition, and formed a thick,
grey, creamy layer covering the surface. The individual rods
measured about 3°5 in length. They were either scattered
singly or were associated in series of two, three, and sometimes
of four. Their breadth was about 0°92. Many of the still
Fic. 3.—Bacilli passing into spore formation x 1000.
ones had already passed on into spore formation, and in doin
so seemed to become somewhat shorter and thicker (Fig. 3).
Subsequently the whole of them assumed this condition, and
ultimately the bacillar coating was replaced by a thick gelatinous
layer of the free spores. No traces of Ozdiwm or of other fungi
ever manifested themselves.
During the great increase of acidity occurring coincidently
with the development of Oidium the zoospores rapidly become
motionless, disintegrate, and disappear. The rate at which they
do so is curiously rapid. Frequently within an hour a portion
of the material, which at first showed numerous characteristic and
active zoospores, retains no recognisable traces of their presence,
and im some cases a period of ten minutes is sufficient to produce
most marked changes. That this effect is not to be ascribed to
246 D. D. CUNNINGHAM,
change in temperature of the medium is demonstrated by the
fact that when isolated portions are kept saturated with suitable
fluids of an alkaline nature, such as the fluid of choleraic ex-
creta or solution of cow-dung, the zoospores retain their activity,
and even increase considerably in number, due to processes of
division, for hours and even for days. This was most clearly
shown by a prolonged series of experiments, in which the phe-
nomena in such saturated portions, isolated beneath cover-glasses,
were compared with those occurring in the material from which
they were derived when left to undergo the normal course of
changes.
A certain degree of concentration of the basis seems also, in
most cases, to be essential to the continued life of the zoospores,
as while those which remained in the interspaces between the
solids of the basis continued in uninterrupted activity, others
which found their way by their own movements, or by the action
of currents, into the peripheral fluid of the preparations, as a
rule, rapidly went through the series of changes previously
described, and passed on into disintegration. The changes
occurring in the natural basis seem to be completely fatal to the
zoospores, as no reappearance of them was ever observed to occur
after the medium had, passed on into the alkaline condition,
though, as we shall subsequently find, it is then thoroughly
adapted to them when artificially introduced.
The zoospores are not the only infusorial organisms which
are prejudicially affected by the initial fermentive changes occur-
ring in the excreta, for the amceboid bodies and the bacteria are
similarly affected. Leaving the effects produced on the former
for future consideration, it may be well here to examine those in
the case of the bacteria a little more closely. The first point to
note regarding them is that the phenomena differ from those
observed in the case of the zoospores. ‘There is no evidence
here of any complete destruction of the organisms. There is
merely a temporary suppression of development succeeded by
excessive activity of it. The phenomena are parallel to those
occurring as the result of prolonged boiling of the medium.
Whether, however, we are to regard the subsequent development
as due to renewed activity in preformed bacterial elements which
have merely passed into temporary inaction due to the state of
the medium, or whether we are to suppose that these are de-
stroyed, and are to regard those subsequently appearing as the
product of spores, remains an open question. In any case,
while there is no reappearance of zoospores, an excessive de-
velopment of bacterial elements invariably succeeds that of
Oidium.
While discussing questions relative to the occurrence of
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 247
bacteria in the excreta, it may be noted that the results of the
present series of observations are entirely opposed, in certain
respects, to those at which Nigeli appears to have arrived in
Enrope. In his work ‘ Die niederen Pilze in ihre Beziehungen
zu den Infections-krankheiten und der Gesundheitspflege,’ he
affirms that, although bacterial elements are constantly present in
very large numbers within the digestive canal, they are invariably
inactive, and on this view he accounts for the absence of ill
effects coincident with a constant source of infection of the
system at large, by what he regards as pathogenic agents. He
affirms that it is inconceivable that bacteria should enter the
system from the digestive canal—“ weil sie ndmlich im Magen
und im Darmkanal zuerst durch die freien Stiuren dann durch die
Salze der Galle geschwicht und bewegungsunfihig gemacht sind.
This statement can, I believe, only be founded on general prin-
ciples, and not on actual observations, unless, indeed, the latter
give very different results in Hurope from what they do in India.
In India there can be no doubt thatthe lower portion of the
intestinal canal very frequently, indeed, normally, contains very
large numbers of active bacteria. After becoming acquainted
with this very sweeping statement of Nageli’s I made an ex-
tended series of special observations on this point. The
results arrived at were as follows:—A very large proportion
of the alvine excretal matter, on its escape from the body, is
composed of immense accumulations of bacteria. In very
many cases these are in active motion, and in others begin to
move at once, whenever a suitable fluid is employed to dilute the
basis. Movement is not confined to cases in which the reaction
of the basis is alkaline or neutral ; it very frequently is present
coincidently with distinct acidity. Fluidity of the materials
naturally favours the movement, but the capacity for active
movement is in very many cases merely concealed, and not
absent when the basis is much concentrated, as is clearly
shown by its immediate occurrence on dilution. Depression
of temperature of the basis causes temporary cessation of activity,
as demonstrated by experiments conducted when the air tempera-
ture was comparatively low, in which repeated disappearance and
reappearance of movement occurred coincidently with depression
of the temperature of the material below that of the body and
its subsequent elevation to it, the movements referred to being
not, of course, mere molecular movements, which might be
ascribed to movements established in the fluid, but active darting
progressive ones. The addition of water to the basis at once
causes an abolition of movement.
It must, I believe, be due to the effects of depression of tem-
perature and employment of unsuitable media for dilution that
218 D, D. CUNNINGHAM,
active bacteria have been asserted not to be present within the
intestinal canal. In certain portions, at all events, of the intes-
tinal canal they are almost invariably present in great numbers
in an active condition, and the belief that an incapacity for
movements prevents their entrance into the system, therefore,
falls to the ground.
Even where present in great numbers and extreme activity, a
total disappearance of movement in the bacteria coincides with
the development of acid coincident with the appearance of
Oidium. Only when the latter has matured, and coincidently
with the appearance of alkalinity, do active bacteria again present
themselves. When once they begin to appear, however, their
development goes on with intense activity, and quickly runs
through its various stages to the formation of the so-called
“ spores.”
The ameebal organisms occurring in the excreta remain to be
considered. Like the zoospores, they occur in the excreta
during health, as well as in cases of cholera and other morbid
conditions affecting the intestinal canal. Their presence seems
to be determined by the same conditions as those regulating the
presence of the zoospores; only, due to the readiness with
Fig. 4.—Encysted excretal Ameba x 1000.
which they assume an encysted condition, and thereby are
enabled to resist the influence of detrimental conditions (Fig. 4)
they may possibly be rather more constantly detected in one or
other form than the other bodies are. Owing to their having
assumed an encysted state, they may be recognised in media
where they could not maintain activity, and even for considerable
periods in such as have proved fatal to them, the strong capsule
of the cyst preventing the content-protoplasm from undergoing
disintegration for some time after its vitality has been destroyed.
Due to this, in examining excreta for amebal organisms, we
must be prepared to recognise both still and active conditions,
and in regard to bodies representing the former, it is necessary
to guard carefully against mistaking them for oily particles, or
vice versa.
In both theactive and encysted condition they exhibit great varia-
tions in size, the variation in this respect being specially marked
in active specimens, asin different media and at different times in
the same one they not only seem to vary in absolute bulk, due to
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 249
differences in nutrition, but they also vary in the form and extent
of the pseudopodial extensions of their substance. In some cases
isolated thick pseudopodia alone are emitted from the more on
spherical body (Plate X VIII, fig. 19), while in others this condi-
tion is exchanged for one in which the body is spread out in all
directions into an irregular, constantly changing proteplasmic
flake. Between these two extremes a connecting series of
intermediate forms exists, and the transition from one to the
other through these can frequently be observed to take place in
individual specimens. In the encysted condition, when their
form is more or less spherical or elliptical, they frequently attain
a diameter of 25 w or even more, and they may range down-
ward from this until the diameter only amounts to 8 yu.
The body-substance is sometimes almost homogeneous, at
others more or less distinctly granular, due seemingly to the
presence of extraneous nutritive matter. Changeable vacuoles,
often of considerable size, may or may not be present ; but a true
contractile vesicle seems to be almost always, if not invariably,
wanting so long as they are retained in the original medium.
Fic. 5.—Large nucleated excretal Amceba x 1000.
As in the case of the zoospores, considerable variation exists in
regard to the presence of a defined nucleus. In some cases no
recognisable traces of such a structure are present, but in others
a permanent clear nuclear area is visible. ‘This may or may not
include an evident nucleolus (Fig. 5). When present, the latter
may attain a diameter of 7 to 9 w. It is circular and appa-
rently discoid, but in some cases may appear annular from the
presence of a thickened margin.
The degree of movement which the Amcebe present in different
cases varies greatly. In some the movement is extremely
energetic, the body forcing its way rapidly between the sur-
rounding masses of debris. In others it is confined to changes
of form and slow emissions and retraction of protrusions without
change of place, and in still others the only signs of it present
are the gradual appearance and disappearance of vacuoles, or
other indications of content-change. Any direct multiplication
of Amcebe by division does not appear to occur, or if it do so,
must occur with extreme infrequency, as, though carefully
VOL, XXI,—NEW SER, R
250 - D,. D., CUNNINGHAM.
watched’ for in very many cases, it was never seen to take
place.
In many normal excreta in which Amcebe are present in con-
siderable numbers, they are all in a state of inactivity, and more
or less completely encysted. In such cases they may frequently
be roused to activity by the addition of suitable media which are
found in the same liquids which have been already indicated as
adapted to the zoosporic bodies. Kven when seemingly most
distinctly encysted no trace of an envelope is left behind on the
emergence of the Amcebz, the cell-wall apparently undergoing
complete resolution during the process. When they have
emerged, the Amcebe do not exhibit such extreme susceptibility
to changes in external conditions as the zoospores do, for they
may often be seen to make excursions in the peripheral zone of
nutritive fluid in diluted preparations without showing any
symptoms of immediate detriment. In some cases the still and
encysted Amcebze present in the excreta cannot be roused to
activity by an addition of nutritive fluid.
Like the zoospores, the Amcebe are very rapidly affected by
the changes normally occurring in the excreta after their exit
from the body. The rate at which this occurs is, perhaps, not
quite so rapid as in the cases of the zoospores, but the final
result, in so far as the vitality of the organism is concerned, is
the same. With the increased acidity and the development of
Oidium all activity ceases and the organisms either encyst or
break up and disappear. When encystment occurs they remain
for long recognisable in the medium, and may often be detected
in the latter even after the acid fermentation has run its course,
and has been succeeded by the alkaline one. So far as vitality is
concerned, the result is the same, however, whether encystment
occur or not. The acid stage is fatal to them, and they never
revive with the development of the alkaline one. As in the
case of the zoospores, so with the Amcebe, no reappearance ever
seems to take place in excreta which have passed through the
acid fermentation, unless due to the introduction of extraneous
germs, and this although the medium, when once it has become
alkaline, is eminently suitable to them.
In addition to those which can be recognised as encysted or
still Amcebze, there is another’ class of bodies frequently present
in the excreta which were for long a subject of investigation ere
their true nature could be determined. These bodies are, I
believe, identical with certain of the bodies long ago observed
by Drs. Swayne and Brittan,’ and subsequently described by
Professor Hallier as spores in his celebrated treatise on the
1“ Account of Certain Organic Cells peculiar to the Evacuations of
Cholera,” ‘ Lancet,’ 1849, pp. 368—398 ; ‘ London Medical Gazette,’ 1849.
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 251
fungoid origin of cholera! They consist of spherical or
elliptical cells of various sizes, ranging from 3°5 to 9°2m in
diameter, and frequently characterised by the brightly refractive
oily appearance of their contents (Plate XVIII, figs. 20, 21).
This latter character is not by any means an invariable one, how-
ever, for in other cases they are finely clouded or molecular, and
with more or less distinct vacuolation ; and the passage from the
one condition to the other may readily be observed to take
place specially under the influence of changes in the nature of
the medium. They appear to consist of a very delicate mem-
branous sac enclosing a mass of varying content-matter. They
may either occur scattered singly through the basis or may be
associated in groups, and, in the latter case, may sometimes be
observed to be connected with one another by a delicate gela-
tinous, intercellular basis, which, I take it, represents the struc-
ture described by Hallier as the sporogenic cyst (Plate XVIII,
fig. 20). As a rule, their occurrence is associated with that
of zoospores and Amcebe, but in some excreta they are present
apart from such bodies. The nnmber present in the excreta
during health varies very considerably. In some cases of intes-
tinal disorder they are present in increased numbers, but never
apparently are they so very abundant as 7m certatn cases of cholera.
In the normal excreta in health they are very transitory, dis-
appearing like the zoospores very rapidly with the increasing
acidity of the medium, so that specimens which when quite recent
showed an abundance of them may, within the course of twenty-
four hours, retain no traces of their presence. Like the zoo-
spores, too, they are very susceptible to the influence of other
changes in their surroundings, rapidly disappearing when they
happened to be washed out into the ring of nutritive fluid
surrounding the thicker portion of a preparation. Owing to
their rapid disappearance from the unmixed excreta, it is hope-
less to attempt their continuous investigation without the aid of
suitable nutritive media; and of these, that which I have found
to act most satisfactorily is the solution of cow dung which has
been already mentioned as adapted to the requirements of the
zoospores and Amcebee. Under the influence of this they may
often be preserved for several days, and continued observations
of various developmental changes occurring in them may thus
be carried out. The results of such cultivations seem to me
to have clearly shown that these enigmatic cells are reproductive
bodies belonging to the Amcbe, and forming a connecting link
between these and the zoospores,
A suspicion that they really were products of reproductive
processes occurring in the Amcebe was originally aroused by
1 ¢Das Cholera Contagium,’ Leipzig, 1867.
252 D. D. CUNNINGHAM.
certain cases in which the fresh excreta contained Amebe, within
which varying numbers of bodies, indistinguishable from them,
were present (Fig. 6). As, however, the amcebz were in some
Fic. 6.—Large excretal Ameba containing sporoid bodies x 1000.
cases still active, and only differed from their compeers in not
being provided with a distinct nucleus, it appeared at first very
doubtful whether the phenomenon was not due rather to the in-
gestion of extraneous bodies than to any process of intrinsic
development ; although, on the other hand, it seemed strange
that in isolated cases such an ingestion should have occurred
simultaneously in numerous Amcebz, while in the vast majority
of cases in which the latter coexisted with the sporoid cells, no
evidence of the occurrence of any such process presented itself.
Further observations appeared clearly to show that whatever
interpretation ought to be put on the above described pheno-
menon, the sporoid cells really are developed from the Amebe.
The process of formation normally occurs coincidently with
the cessation of activity in the parent, so that it is possible that
in those cases in which sporoid cells were present within active
Amcebee, they may have been derived from without. As, how-
ever, the preparations in which the phenomenon was observed
had been treated with nutritive fluid, it is quite possible that
it was due to an abnormal resumption of activity in Amebe
which had passed into the preliminary stages of reproductive
multiplication. The phenomenon may, in fact, have possibly
been parallel to those observed in the sclerotia of the Myxo-
mycetes under the influence of favorable nutritive conditions.
The plasmodia of the latter organisms, in passing into the sclero-
tial state, break up into a multitude of distinct spheres, each of
which is capable of independent activity, and of emerging as a
distinct amceboid body when separated from its neighbours and
introduced into a suitable medium, but which may also melt
together to reform a common plasmodium when the sclerotium,
as a whole, is exposed to conditions favouring its activity. As
the whole of the body-substance of the Amcebee is not expended
in the formation of the sporoid cells, a portion remaining in the
form of a common gelatinous investment, and as the latter, cer-
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 253
tainly in some cases, retains a certain degree of contractility
and capacity of altering its form for some time after the forma
tion of the reproductive cells has begun, | am inclined to regard
the latter explanation of the phenomena in these exceptional
cases as the true one.
The process of spore formation is not preceded by any true
encystment ; the parent body merely loses its active progressive
movements and form-changes, and a very delicate surface layer
becomes, in some degree, differentiated upon it. The content-
substance within this next begins to show a constriction, divid-
ing it into two lobes, and a gradual extension of the process ends
in the separation of these as independent masses (Fig. 7). The
Fic. 7.—Formation of sporoids x 1000.
entirety of the material of the parent does not, however, as
before mentioned, seem to be expended thus; but a varying
amount remains as a gelatinous intercellular matrix, which blends
with the surface layer (Pl. XVIII, fig. 20). Under favorable
circumstances, each of the daughter bodies originally formed, as
described above, in its turn divides into two, and in this way
groups of sporoids, containing large numbers of individual cells,
may be actually observed to arise in the course of forty-eight to
seventy-two hours (Fig. 8). Hach of the bodies thus formed by
|
Fic. 8.—Group of sporoids developed from an Ameeba x 1000.
division acquires a delicate investing layer, but the process of
254 D. D. CUNNINGHAM,
division may undergo arrest at almost any stage, and fusion of
the partially differentiated bodies may then take place. The
extreme variation in the size of the sporoids in different excreta
thus finds an easy explanation in the processes by which they
are formed. Where the processes of formation go on undis-
turbed in the medium, as, for instance, where the development
occurs in specimens beneath a cover glass, the sporoids remain
aggregated in groups embedded in their gelatinous bases, and
exactly resembling those described and figured by Hallier. Due,
however, to the tenuity of the matrix, they are readily detached
from one another, and scattered under the influence of slight
mechanical disturbances, and hence in the excreta in their
nutural condition it is rare to encounter any save isolated
individuals.
The sporoid cells thus arising by processes of division within
the Amcebe, we have next to inquire into their subsequent his-
tory. In cultivations of excreta, in which their development has
been followed thus far, no further vital change appears to take
place within them. The medium, sooner or later, seems to be-
come unsuited to them, and they disintegrate and disappear.
It is different, however, in the case of spores which have been
developed within the intestinal canal of the host, for many of
these, when exposed to favorable influences, appear to give origin
to zoospores. ‘The phenomenon of the origin of the latter may
frequently be observed in specimens of fresh excreta, which have
been treated with nutritive fluid. Under such circumstances
media, which at first contained an abundance of sporoid cells
and no zoospores, may within a few hours be found to contain
hardly any of the former and numbers of the latter; the pro-
portion of zoospores present at the close of the observation
being in direct relation to the numbers of sporoids originally
present and the proportion in which they have subsequently
disappeared. It is difficult precisely to follow the stages in the
process, as it only takes place in the thicker portions of the
preparation—the sporoid cells, as before said, being rapidly
destroyed when washed out into the surrounding fluid—but the
cell wall of the sporoid seems to become gradually softened and
absorbed, and does not remain behind as distinct cyst. It has
unfortunately never been possible continuously to follow out the
transition of any individual Amcebe into a mass of sporoid cells,
and the resolution of the latter into zoospores. Amcebe have
been seen to give rise to sporoids in some cases, and the origin
of zoospores from bodies apparently in every respect indentical
with these has been observed in others, but a link is still wanting
in order to render the observation quite complete. In spite of
this, however, there can, I believe, be little doubt that the
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 255
Ameebe, sporoid cells, and zoospores really constitute stages in
one cycle of development, more especially when certain observa-
tions, an account of which will be met with farther on, are taken
into account. Any direct origin of Amcebe, from characteristic
sporoid cells in human excreta, does not seem to take place.
Allowing, then, in the meantime, that the characteristic zoo-
spores, Amcebze, and sporoid cells occurring as parasites within
the human digestive canal are all members of the developmental
cycle of one specific organism, how can we account for the
extreme frequency with which they are present? ‘Taking the
very great susceptibility of the organisms to the influence of ex-
ternal conditions, and the fact that the media in which they
escape from the body seem, as a rule, to undergo changes cer-
tainly fatal to them, it appears at first sight very difficult to do
so satisfactorily. We might, indeed, take refuge in the suppo-
sition that, after the germs have once obtained an entrance, they
remain persistently within the body, giving rise to constantly
recurring generations of the parasite, but such an hypothesis is
hardly consistent with the fact that in the case of a given indi-
vidual they may appear suddenly after considerable intervals of
apparently entire absence, and after persisting for varying periods
may again vanish, only to reappear as before at a later period.
We should, therefore, be compelled farther to assume that
periodical retentions, either of the germs or of the developed
organisms, take place somewhere within the body, and alternate
with uncertain periods of discharge, or that their appearance and
disappearance from the excreta is determined solely by conditions
in the latter allowing or preventing their persistence in the
contents of the lower portion of the digestive canal.
While allowing the possibility of such explanations, I do not
regard them as correct, but believe that the appearance and dis-
appearance of the parasitic forms are due to the successive in-
troduction of extraneous elements and the subsequent discharge
of the result of their development. It is as difficult to give a
definite opinion as to the precise source of these organisms as it
is to state whence the oidial and bacterial elements of the intes-
tinal contents are derived. They are, as has already been pointed
out, almost constantly present in varying numbers in the intes-
tinal canal, and are in all probability introduced with ingesta of
various kinds,
Il. The Intestinal Monads and Amebe of Cows and Horses.
It is now more than five years since, whilst studying the
development of Pilobolus crystallinus, I first encountered what
it appears may be regarded as the perfect fructifying or repro-
256 D, D. CUNNINGHAM.
ductive bodies of these intestinal organisms. In a specimen of
recent cow dung, which had been reserved in a moist chamber
for twenty-four hours, the surface was found to be studded with
a multitude of minute glistening white spherules, adhering to
projecting points of the basis (Pl. XVIII, fig. 1). At first sight
these were regarded as basal dilatations of Pilodolus, in which
an abnormal suppression of colouring had occurred, bnt on sub-
mitting them to microscopic examination this was found not to
be the case. ‘They were entirely uneonnected with the mycelial
tubes of the fungus which subsequently produced an abundant
crop of normal fructification, and did not resemble the basal dila-
tations in structure, consisting of a membraneous sac crowded
with spore-like bodies. These were circular, flattened, and
biconcave, closely resembling red blood-corpuscles in general
appearance. On being introduced into a solution of cow dung
they rapidly became spherical, a contractile vesicle appeared
within them and began to pulsate, and they sooner or later, as a
rule, gave exit to minute amebal bodies, which crawled off
freely in the fluid, generally leaving a delicate cyst behind them
in doing so. In other cases, however, in place of being resolved
into Amebee, they appeared to give origin to flagellate zoosporic
bodies. Similar phenomena were observed at various subsequent
periods, and the sporangic bodies being not unnaturally regarded
as representing some low Myxomycete form, a repeated but futile
search was made for the presence of plasmodia corresponding
with them. Subsequently the appearance of these sporangic
bodies came to be recognised as a normal and almost invariable
event in specimens of cow dung reserved for the study of sterco-
reous fungi. The essential condition ensuring their appearance
seemed to be that the basis should have been secured and set for
cultivation whilst still quite recent, older samples almost in-
variably failing to produce a crop, or only producing a very
scanty one. As the result of numerous experiments, it was
ascertained that the appearance of these sporangia preceded that
of any other form of fungal fructification, occurring, as a rule,
within twenty-four or forty-eight hours from the commencement
of a cultivation of perfectly fresh material, and being succeeded
by that of various fungi in the following order :—Pi/odolus crys-
tallinus, Ascobolus sp., various species of Gymnoasci, Peziza
sp., Coprinus sp. These fungi may be regarded as the regular
and almost invariable results of the cultivation of fresh cow dung
in this part of India, while occasionally other forms are interpo-
lated in the series, as, for instance, a Syncephalis, which some-
times attacks the Pilobolus. Taking the normal series of
developments, the sequence of events is shown in the following
table ;
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 257
Sequence and Periods of Development of Fructifications
appearing on Fresh Cow Dung.
White sporangia . : , . after 24 hours.
Pilobolus erystallinus ae
Ascobolus sp. , : : about 5 days.
Various Gymnoascal forms . : : if =
Peziza sp. . ; ; : : +) en
Coprinus sp. 3 ; 3 : 3; & weeks.
Further investigations showed that the occurrence of these
sporangia was not limited to cow dung, but also frequently
occurred on horse dung too, where, as on the other medium,
it preceded that of Pilobolus, or other forms of mucorine
fungi.
Even after the study of these sporangioid bodies was specially
undertaken, it was not until after many months of continuous
investigation that their true nature and mode of origin were
satisfactorily determined, and that their relation to organisms,
seemingly identical with the parasitic zoospores and Amcebe of
the human excreta, was ascertained. In studying the develop-
ments normally occurring in reserved specimens of cow dung as
compared with human excreta, one of the most conspicuous
differences presented by the media is that the former has no
tendency to pass through the acid fermentation so constantly
affecting the latter medium. Perfectly fresh specimens are
either neutral or faintly alkaline in reaction, and when kept
under observation exhibit a constant progressive development of
alkalinity, so as to become strongly alkaline within twenty-four
or forty-eight hours—a condition which they retain for indefinite
subsequent periods. Another point distinguishing vaccine from
human excreta lies in the relative amount of bacterial elements
originally present in them; for while, as we have already seen, a
very large proportion of the mass of the latter medium is formed
of these elements, the proportion of them present in a developed
form in the former appears normally to be very small. Farther
when the medium follows a normal course in reference to the
organic developments occurring in it, there is at no period that
excessive multiplication of bacterial elements so characteristic of
the later stages of decomposition in human excreta, the numbers
and succession of fungal organisms appearing to a great extent
to exhaust the nutritive properties of the basis. The two com-
monest forms of bacteria occurring in cultivations of cow dung
are shown in the accompanying figures (Figs. 9, 10).
The evidences of exhaustion of the basis, in so far as concerns
certain of the organic developments which have occurred in any
abundance of it, is unequivocal, each of them appearing in its.
turn and then absolutely and permanently dying out. The
258 D. D. CUNNINGHAM.
phenomenon is specially marked in reference to the sporangioid
bodies and P2dodolus, which, as we have already seen, are the
Fic. 10.—Slender Bacterium common in cow dung X 1000.
first forms which make their appearance. Crops of sporangia
are rarely produced for more than two or, at utmost, three
days, and crops of Pz/obo/us for more than six or seven, and in
this case it is only for two or three that the development is
abundant. We have an enormous primary production of repro-
ductive bodies and an absolute, or almost absolute, failure of
any further development due to these. Where the primary crop
has been abundant, it is very questionable whether the repro-
ductive elements then produced ever germinate in the same
medium in which they were produced; for although, as before
said, successive crops of fructification appear for two or three
days, these apparently all belong to one generation. This cer-
tainly is the case in so far as Pilobolus is concerned; there is
no evidence of successive generations of mycelia, and the suc-
cessive crops of fruit are in many cases visibly the result of
unequal rapidity in the development occurring in basal diluta-
tions contemporaneously developed. The phenomenon is clearly
one of exhaustion of the nutritive basis, and not due to defec-
tive germinal energy or the reproductive elements ; for we have
only to transfer some of them to a suitable fresh basis to secure
their immediate development. While in the primary basis we
find the surface covered with masses of reproductive elements
totally incapable of farther development, so long as they remain
there, we have only to transfer a few of them to an unexhausted
MLCROSCOPIC ORGANISMS IN INTESTINAL CANAL. 259
basis in order to secure an abundant production of a fresh
generation. This is of course merely the parallel of what we
find occurring in regard to the Ozdium and bacteria of human
excreta, where a solitary and excessive development of the organ-
isms occurs, terminating in the production of innumerable re-
productive elements incapable of germination until transferred
toa fresh medium. In the case of cow dung, we certainly cannot
ascribe the failure of excessive bacterial development to exhaus-
tion by organisms of the same nature; but the variety and
succession of other organisms which are developed may, perhaps,
practically produce a similar result.
While fresh cow dung is relatively deficient in bacteria, it is
by no means devoid of distinct organisms generally. On the
contrary, we find it almost invariably containing a very large
number of zoosporoid bodies (Pl. XVIII, fig. 17), and some-
times smaller numbers of other infusorial forms of various kinds.
After prolonged study of the zoospores under various circum-
stances, I am unable to indicate any coustant differences to
distinguish them from those of human excreta. Like the latter,
they exhibit numerous varieties in form and in character of
movements, but none of these are peculiar to them. They seem
also to be similarly affected by reagents artificially added to the
basis, or by spontaneous changes taking place in it, and altogether
there can, I believe, be no doubt of the identity of the organisms
in both media. Although so constantly present, they may, like
those of the human excreta, readily escape detection, unless
suitable precautions are taken in preparing the specimens for
examination. A dilution of the basis with pure water is fre-
quently so rapidly fatal to them as almost entirely to conceal
their presence, and even other solutions more favorable to them
must be added with caution so as to avoid too abrupt a change
of conditions. The best method of treating preparations, with
a view to their detection, is to spread out a minute portion of
the basis in a thin layer on a slide, then apply a cover glass, and
(having first focussed a field containing a view of a portion of
the margin of the layer) to introduce some strong solution of
the same dung from which the specimen was procured, and
which has been previously filtered, boiled, and allowed to cool.
On doing this, the organisms may be observed emerging from
the margin of the basis, and, after swimming actively in the
fluid for a short time, gradually passing on into the series of
changes described as occurring in those of human excreta under
similar circumstances. Here, too, we find that those which, in
place of emerging into the peripheral fluid, enter some of the
interstitial spaces existing between the solids of the basis, retain
their vitality much longer than their neighbours,
260 D. D, CUNNINGHAM,
The number of zoospores which may be detected in this way
is in many cases very remarkable. The size of individual speci-
mens varies much, which is no doubt greatly dependent on the
frequency with which processes of division recur in them. Very
often they measure about 10 y in length by 5 or 6 w in breadth.
The number of flagella with which they are provided also varies
from one to three or four; whilst in full activity, neither nucleus
nor contractile vesicle can be detected as a rule, and after treat-
ment with Liquor Iodi they may or may not exhibit a nucleoloid
particle. The latter reagent generally induces a peculiar series
of phenomena. ‘The body gradually loses its natural fusiform,
or pear-shaped outline, and becomes circular and motionless.
Shortly after it has ceased to move, a large vesicular protrusion
is emitted at one or other point from the somewhat granular
body, and general disintegration soon sets in. ‘There is no evi-
dence of any differentiated surface layer, and the flagella appear
to be merely transitory and changeable protrusions of the pro-
toplasm. The point opposite to the flagellar site seems to be
that through which nutritive materials are absorbed, the body
becoming attached to foreign particles by it, and being some-
times drawn out in consequence into a caudal process or filament
of variable magnitude. Allthe characters which the zoospores
here present are, in short, identical with those occurring in the
human parasite. The processes of multiplication are also simi-
lar, consisting in transverse division preceded by diminution or
temporary arrestin activity, and the phenomena attending dim-
inished vitality and disintegrative disappearance follow the same
course.
While, however, the human and vaccine parasites appear to be
identical in nature, their presence in the excreta is followed by
different results. In the case of the human parasites we have
already seen that a rapid and complete process of destruction
sets in coincident with the changes normally occurring in their
medium after its exit from the body, but this does not hold
good inthe case of the vaccine parasite. That it does not is
probably due to the absence of any fermentive change in the
medium corresponding with the acid development coincident with
the appearance of Oidiwm. In place of disappearing from
the medium the organisms in the cow dung, after continuing to
multiply by division for some time, seem to pass on to further
stages of development through which they are enabled to give
origin to reproductive bodies providing for the perpetuation
and diffusion of the species, or where conditions are unsuited to
this, to resting forms capable of renewed activity on again en-
countering favorable conditions. The fully developed repro-
ductive bodies consist of the sporangia, which have been
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 261
already mentioned, the resting conditions are represented by
encysted zoospores or much more frequently by encysted amoeboid
bodies.
The following notes recorded in reference to the phenomena
observed in a specimen of cow dung are generally typical of
those in numerous other experiments of a similar nature. Some
perfectly fresh cow dung was procured and set in a moist cham-
ber at 10.30 a.m. The material was moist, faintly alkaline in
reaction, and swarmed with large active zoospores. Five hours
later a second preparation was taken from the specimen. In
this an even greater number of active zoospores was present
than in the first, and a certain number of still ones was also
recognisable. A third preparation, procured seven hours later,
showed no active zoospores but an abundance of still ones of
oval and rounded form. After another interval of six hours a
fourth specimen was taken and found to resemble the previous
one in character save that a distinct contractile vesicle was
visible in many of the cells. At this time (dawn) no signs of
sporangia were visible, but a few hours subsequently they ap-
peared in great abundance, while preparations of the basis showed
an abundance of active ameboid bodies of various sizes, ranging
from that of the still zoospores upwards.
Similar phenomena repeat themselves with monotonous uni-
formity in successive experiments. Again and again we find a
basis abounding with zoospores; increase in the numbers of
these bodies for some time; a cessation in their activity; the
appearance of multitudes of bodies agreeing in size and form
with the inactive zoospores, but characterised by the presence of
a contractile vesicle; the emergence and growth of these as
active amceboid bodies and the appearance of sporangia. That
the latter are certainly the product of the union of the ameboid
bodies is clear from the result of other observations, but, as
necessarily is the case in all massive cultivations, the evidence
connecting the zoospores originally present with the amceboid
bodies subsequently appearing remains imperfect. That the
relation is one of identity is, no doubt, rendered probable by the
fact that the excreta in the fresh condition never show any
proportion of ameeboid bodies or of still cellules capable of
accounting for the enormous numbers subsequently present,
unless an excessively rapid multiplicative division were assumed
to take place from the scanty supply originally present. An
assumption of this nature is, however, entirely devoid of any
support from observation, as any division of the ameboid bodies
previous to sporangic formation never appears to occur. On
the other hand, we have the zoospores present in abundance
from the outset, and capable of very rapid multiplication by
262 D. D. CUNNINGHAM.
division ;! we find that it is impossible to distinguish between
resting zoospores and bodies which pass on into an ameeboid
state; and we know that the zoospores merely differ from
Ameebee in the character of the protrusions which they emit, and
therefore in the nature of their movements. Allowing the
identity of the two forms, we have a ready means of accounting
for the regularity and abundance of the crops of sporangia and
the general ratio of these to the numbers of zoospores, while
rejecting it we have no explanation to give of the appearance of
the multitudinous development of ameeboid bodies.
In the endeavour to obtain more positive evidence on this
point, hundreds of cultivations on a small scale were carried
out with more or less satisfactory results. In some cases there
appeared to be no doubt that the zoospores originally present
became converted into Amcebe at a later period, but the
difficulty of attaining to absolutely certain results appears to be
almost insurmountable. In the first place, in order to render
any such cultivation susceptible of continuous observation, it is
necessary to introduce conditions which we have already found
to exert a most prejudicial effect on the vitality of the zoospores,
for the basis must necessarily be diluted with some fluid in
order to render the organisms visible. A condition of fluidity
of the basis, too, independent of any actually destructive effects,
certainly influences the occurrence of developmental processes
in other ways. ‘The persistence of zoospore forms may be pro-
longed, and the appearance of amceboid ones be delayed by an
excess of moisture as may readily be proved by experiment. So
again an excess of fluidity in the medium seems to be one of
the agencies capable of causing ameeboid bodies present in it to
assume the encysted condition in place of passing on to the
normal sporangic development. Another great obstacle to the
satisfactory decision of this question lies in the excessive and
constant movement of the zoospores, which renders it impossible
to secure any individual specimen for continuous observation
over a prolonged period.
All that can be positively affirmed is that the ameeboid bodies
which replace the zoospores primarily present appear to be
directly derived from the latter, and that the two forms seem
merely to represent different developmental stages of one and
the same organism, connected with one another by the interven-
tion of an inactive stage.
The Amcebe, when they first appear, are of very minute size,
ranging from 5 » to 7 « and upwards in diameter when ina
spherical condition (Pl. XVIII, fig. 1). In some cases a
1 Processes of division have been observed to recur in one body twice in
the course of an hour.
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 263
contractile vesicle is at once distinctly visible within them; in
others such a structure can only be detected with extreme
difficulty, and in still others it appears to be absent. The same
inconstancy seems to prevail in regard to the presence of a
nucleus and nucleolus. Generally, I believe, a clear nuclear
area is visible at a comparatively early stage, but a differentiated
nucleolus often does not appear until much later; when it does
appear it is as a flattened circular disc in the nuclear area. The
rate of growth in the Amcebe and the size ultimately attained
ere the occurrence of sporangic formation varies very much,
apparently in accordance with the nature of the medium. In
favorable cases it is wonderfully rapid, and where the growth is
considerable, it is usually associated with further development
of the nucleus (Pl. XVIII, fig. 10). A division of the nucleolus
occurs, and the resultant bodies move somewhat apart, so that a
pair of greenish discs replace the originally solitary one.
Farther than this the nuclear area seems to become differen-
tiated from the rest of the body-substance by a boundary layer,
and a cross partition of similar nature passes inwards to separate
the nucleoli (Pl. XVIII, fig. 15).
Fic. 11.—Cornuate Amcebe x 180.
The characters of the movement also vary greatly in different
specimens, and in one and the same specimen at different times.
Sometimes it is of a free flowing character, the organism moving
rapidly forward by means of successive protrusions of its sub-
stance. In other cases we find such movement alternating with
a more sluggish action, in which the body presents an irregularly
lobed or cornuate form, and only gives origin to limited exten-
sions (Fig. 11). This condition frequently seems to coincide
with defective nutrition, as the addition of fresh nutritive matter
will often cause it to be exchanged for free progression. In
still other cases again the body assumes a peculiar flattened
scale-like condition, adhering by one surface to the glass of the
slide, and moving forward with a slow gliding motion, accom-
panied with comparatively little change of form (Fig. 12). In
such cases the free surface often shows curious linear markings
due to the presence of longitudinal thickened ridges. Three dis-
264 D, D. CUNNINGHAM.
tinct areas appear to be present in the body in this state; we
have first a dense granular central portion constituting the sub-
Fic. 12.—Ameeba in epithelioid state with dividing nucleolus x 1000.
stance of the ridges and the thicker portions ; beyond this is a
highly refractive area devoid of granules, and external to this
again is a delicate tenuous layer of the protoplasm, often only
distinguishable with difficulty from the surrounding medium.
All the vital processes seem to be carried on in such cases with
extreme slowness. The contractile vesicle dilates very gradu-
ally and often only undergoes imperfect obliteration on contrac- :
tion, or it may remain absent for prolonged and uncertain
intervals. In other cases it seems to be rigidly fixed in full
dilatation. In appearing it sometimes is developed from a
single centre, in other cases several minor vesicles appear and
fuse into one as they increase in size. Granules of nutritive
matter are ingested and frequently accumulate in spherical
masses within vacuolar spaces filled with fluid. In other cases,
however, they are irregularly diffused. When in full activity, a
constant succession of fluctuating vacuoles is present in the
body-substance. In some cases, and apparently connected with
or preparatory to the resolution of the body into a collection of
sporoid reproductive bodies—as it only occurs where they have
ceased to move and have become aggregated in sporangoid
masses—the large Amozbz in place of showing at utmost two
large nucleolar bodies as they normally do, contain from three
to eight of smaller size (Pl XVIII, fig. 11). From the appear-
ance and arrangement of these in different cases, there can
be no doubt that the increased numbers are due to repeated
binary division of the nucleoli originally present.
The size of the Amuebe and nuclei varies so extremely in
different cases and at different times that it is impossible to give
any useful average measurements. ‘They very frequently, when
in an irregularly rounded condition, measure from 15 to 25 win
diameter, with nucleoli, which, when paired, have a diameter of
8:5 u, and when in larger numbers measure only half as much or
under. ;
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 265
After continuing to progress through the medium for variable
periods, the Amcebee either cease to move, and remaining more or
less isolated, become encysted, or becoming aggregated into
masses give origin to sporangia. Where they are present in
abundance, and where the conditions of the medium are unfa-
vorable to sporangic development, the accumulation of en-
cysted bodies on the surface often covers the medium with a fine
greyish bloom, which, unless closely examined, may readily be
ascribed to the presence of mycelial elements. ‘The encysted
bodies are either quite free or are associated in little groups and
knots. As arule, no further change appears to occur within
them, and they remain unchanged for indefinite periods, ready
to resume activity when favorable conditions again present them-
selves. In place of becoming encysted, however, we normally
find thea Amcebee, after some time, becoming more sluggish in
their movements, and adhering to one another in pairs or groups
of various sizes, the union becoming very intimate, and in some
cases proceeding to such a degree of apparent fusion that we are
only able to estimate the number of individual elements entering
into the formation of a group by the number of nuclei or of
rigidly dilated contractile vesicles which may persist (Fig. 15).
This phenomenon is so far parallel to that occurring in the case
of various Rhizopodous organisms, such as Actinophrys sol, &c.,
Fic. 13.—Compound body formed of three conjugate Ameebe: x 1000.
but the results following adhesion and union rather resemble
those following the formation of Plasmodia in Myxomycetes, as
the formation of the compound body is distinctly the antecedent
to spore formation, the protoplasmic material becoming in greater
part resolved into a mass of spores or reproductive cells, while a
certain amount of it remains as an investing and intercellular
/ VOL, XXI, —NEW SER, s
266 D. D. CUNNINGHAM.
substance (Fig. 14). All the processes which have been just
Fie. 14.—Ameebal mass breaking up into spores x 1000.
described can sometimes be observed to occur in slide cultivations
beneath cover glasses, and capable of continuous observation ;
but under such circumstances they naturally never attain the
magnitude and perfection exhibited under natural conditions
ae the sporangia are developed on an exposed basis of large
bulk.
In such cases we may trace all stages of the formation of
perfect sporangia from that in which we have mere irregular
ageregations of closely adherent Amcebee (Fig. 15), which on being
Fic, 15.—Irregular aggregate of Amcebe x 180.
detached and introduced into a new nutritive medium become
resolved into their constituent Amcbe (Fig. 16) by resumed
Fic. 16.—Ameeba detached from rudimentary Sporangium x 1000,
activity of the latter, to that in which we have perfectly developed
sporangia, with a distinct investing membrane, and even, in cer-
tain cases, an internal meshwork representing what may be re-
garded as a rudimentary capillitium. The degree to which an
actual fusion of the constituents of the sporangic mass takes
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 267
place varies greatly in different cases and in different portions of
one and the same specimen. Complete fusion often occurs in
the basal portions of pedicillate sporangia, while the process is
only partial higher up. In such cases while we find the stem
consisting of a seemingly homogeneous mass, the head is gene-
rally more or less distinctly marked out into a series of irregular
areas, which are in some cases so defined as to give the surface
when viewed under a low microscopic power a somewhat granular
or faintly nodulated aspect.
The appearances presented by the sporangic masses, where the
constituent Amcebe are yet distinctly recognisable, are very
curious. The surface presents a strangely epithelioid appearance,
due to the dense aggregation of irregular cells closely adapted to
one another, so as to form a continuous layer, while on deeper focus
we encounter sectional views of the interior, consisting of a dense
mass of similar bodies (Pl. XVIII, fig. 3). We havea regular
tissue formation due to aggregation and union of originally
independent elements.
The sporangia vary greatly in size as well as in the extent to
which a distinction between a stem and head is present. In
many cases no stem formation takes place, and the spherical
sporangium is merely attached at one or other point of its cir-
cumference, in others a pedicle of considerable length is present
(Pl. XVIII, fig. 1). The heads may attain a diameter of 0°37
of a millimeter, and the pedicles a length of 0°25. When the
pedicle is of any length it is usually dilated basally into a disc
or into several root-like expansions, which embrace the body to
which it is adherent. The sporangia are almost invariably
situated on prominent projecting points of the basis, such as
minute fragments of vegetable tissue, &c. When developing,
they first appear as minute hyaline prominences or rods project-
ing on the surface of the basis. As their development advances
they become dilated—the dilatation in the rod forms occurring
terminally, and causing them to assume a capitate aspect—and
at the same time an opalescence appears in the previously hyaline
material. This increases in intensity and passes on to opacity,
and the fresh mature sporangia are of a bright glistening white-
ness, passing into various stages of yellow, buff, and amber, as
drying sets in.
On examining many sporangia, even when the constituent
Ameebe are yet recognisable through more or less of their sub-
stance, the presence of a distinct investing membrane may be
made out, and in all mature sporangia such a structure is inva-
riably present. Owing, however, to variations in its structure
under different circumstances, it is much more readily recognisable
in some cases than in others, and may, indeed, sometimes readily
268 D, D. CUNNINGHAM.
escape detection in developing or recently formed sporangia,
which have been kept in a very moist atmosphere; it is very
soft, and quickly dissolves and disappears in water, although
readily visible ere the addition of fluid, and especially so long as
no pressure has been applied. In such cases, too, certain re-
agents, such as Liquor Lodi, readily demonstrate its existence. In
older sporangia, which have undergone a certain amount of dry-
ing, it appears as a distinct, somewhat resistant, and very elastic
membrane, of a yellowish colour. In structure it is finely mole-
cular, and the external surface is covered with projecting organic
corpuscles (Pl. XVIII, fig. 6). In the course of thorough
desiccation again, it appears gradually to disintegrate and more
or less completely disappear, leaving its contents exposed, and
only adherent to one another by intercellular material. Its inner
surface is sometimes distinctly mapped out by a series of promi-
nent thickened ridges into polygonal areas corresponding with the
formative Aincebe (ig. 17).
Fie 17.—Ridges and uepressions on inner surface of Sporangial membrane
x 1000.
After the sporangia have been, as it were, planned out by the
aggregation and more or less intimate union of the Amebe, and
the formation of an investing membrane, the process of spore
formation normally sets in. When this is regularly carried out
the bodies of the Amcebz become resolved into masses of spherical
spores, measuring from 5 to 9 » in diameter. In cases where the
fusion of the parent bodies seems to have been complete these are
indiscriminately massed in the cavity of the sporangium embedded
in an intercellular basis ; where, on the other hand, the process
has not gone so far they tend to adhere in groups of various sizes
corresponding to individual Amcebz, or to small groups of these.
The intercellular material in recently developed sporangia is
soft and seemingly more or less fluid, resembling the intercellular
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 269
matter within Mucor sporangia. Like the material of the
sporangial wall, however, it concretes or sets in drying, so as to
appear in many preparations of partially dried sporangia in the
form of a network, in the interspaces of which the spores are
situated. The character and definition of this vary considerably
in different instances, and in some cases it may be distinctly
resolved into two series of meshes—a larger one, seemingly cor-
responding with the parent Amcebe, and a smaller one with the
individual spores (Figs. 18. 19). Both the sporangial wall and
Fie. 18.—Large reticula of intercellular matrix x 1000,
the intrasporangic network are, when fully developed, stained of
a deep red brown by solutions of iodine, whilst the spores merely
Fic. 19.—Fine reticula of matrix corresponding to spores x 1000.
acquire a yellow tint. No blue colouration follows treatment
with iodine and sulphuric acid, nor does any effervescence occur
under the influence of acids.
The spores, as before mentioned, are, when first formed, of a
spherical outline, or are, at all events, spherical when free, for,
due to mutual pressure, they are frequently more or less polygonal
while within the sporangium. ‘The process of spore formation
270 D. D. CUNNINGHAM.
seems to be preceded by a disappearance of the nucleoli of the
parent bodies, resulting, apparently, as some cases seem to show,
from a process of repeated binary division (Pl. X VIII, fig. 11).
As the sporangia mature and dry the spores lose their spherical
form, a condensation of their substance seems to take place, and
they become biconcave; when in this condition they closely
resemble mammalian. red blood-corpuscles, and, indeed, in many
cases can hardly be distinguished when mingled with human
blood. When in this state the margins measure about 2°7 » and
the central portions about 2°3 » in thickness, the margin being
of a faint greenish tint, and the centre almost colourless
(Pl. XVIII, fig. 7). No evidence of the presence of a nucleus
is, as a rule, present in such spores.
When a mature sporangium containing such biconcave spores
is introduced into a suitable medium, the former very rapidly
swell out and become spherical, and by their increased bulk
exert a constantly increasing tension on the sporangial wall. The
capsule ultimately ruptures at one or more points and contracts,
forcing the spores out in streams and masses into the fluid
(Pl. XVIII, fig. 2). Where the capsule has disintegrated and
disappeared the process of swelling up is accompanied by curious
writhing movements of the spore masses. A contractile vesicle
soon makes its appearance in the spherical spores, which now,
as a rule, show a clear central nuclear area surrounded by finely-
clouded substance, and sometimes apparently containing a
nucleolar particle of a greenish colour (Pl. XVIII, fig. 8 a).
After the contractile vesicle has continued to pulsate for a short
time the body begins to emit a delicate protrusion, and rapidly
unfolds into a minute Amebula, which crawls freely in the
medium (Pl. XVIII, fig. 8 4, ¢, fig. 9). In many cases no evi-
dence of any cyst is left behind, but in others, specially where
the spores are derived from sporangia which have been sub-
jected to prolonged desiccation, such a structure is present,
appearing in the form of a delicate ring after the inmate has
escaped. The spores then, as a rule, give origin to minute
Amebe, but, in certain cases, in place of doing so, they appear
to be resolved into flagellate zoospores, which swim off actively
in the fluid.
The assumption of activity by the sporoids is manifestly
influenced, both by the nature of the fluids into which they are
introduced, and by the conditions to which they have previously
been exposed. When introduced into ordinary pure or distilled
water they remain unaltered for prolonged periods, and either
fail entirely or in greater part to become active. A momentary
exposure to the influence of boiling water, as by dropping the
fluid on sporangia situated on a slide, does not prevent the sub-
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 271
sequent development of the spores. ‘The assumption of activity
is retarded, but a certain number of the spores survive and sub-
sequently give vent to Amcebe. Prolonged boiling, however,
is certainly fatal to them. They are capable of surviving a
twenty-four hours’ immersion in Liquor Iodi, remaining seemingly
unaltered, and becoming active on the substitution of the reagent
by a nutritive fluid. They can also survive immersion for several
hours in 1 per cent. solutions of rectified spirit and of the phar-
maceutical acetic acid. Mineral acids, even in very small pro-
portions, appear to be fatal to them, and hydrochloric acid also
immediately reduces any which are spherical to the biconcave
form. ‘The capacity for resisting various external influences is
also regulated in some degree by the condition of the body. It
is only the condensed biconcave spores which are capable of any
decided resistance, those which are in the dilated spherical con-
dition being much more susceptible to detriment.
Prolonged desiccation appears to influence the rate at which
" activity is developed, but certainly is not fatal. A careful series
of experiments on this point showed that whilst Amcbule
began to emerge from ‘perfectly fresh spores within periods
ranging from fifteen to twenty-five minutes, a gradual retarda-
tion of the process corresponding with different periods of desic-
cation manifested itself, so that, after a period of eighty-two
days, emergence did not occur until within between five to
twenty hours’ exposure to favorable conditions.
When sporangia are introduced into preparations of fresh-
boiled cow dung they rapidly disappear, and the cultivation
within twenty-four hours, in favorable cases, shows an abundant
new crop of sporangia. This process may be repeated again and
again indefinitely so long as a fresh medium is supplied for each
experiment ; for, as in the case of the natural development, the
soil appears to be exhausted in the process of producing a single
crop. Asa rule, in these cultivations we do not find a zoo-
sporic stage represented, the spores at once giving origin to
ameeboid bodies, which, after having increased in size, become
associated to form new sporangia. ‘I'he crops of ‘sporangia thus
produced are, as a rule, peculiarly abundant and well developed
as compared with natural ones, due, no doubt, to the compara-
tive freedom which the organisms here enjoy from a struggle for
existence. In some cases, however, in these artificial cultures
we find a failure of development or a failure of sporangial forma-
tion, the surface becoming covered with a bloom of encysted
Ameebee.
Both in natural and artificial cultivations there is a distinct
tendency to periodicity in reference to sporangial formation. In
the notes regarding one case which were previously given, it is
272 D. D. CUNNINGHAM.
recorded that while at dawn the cultivation showed no traces of
the presence of sporangia, an abundant crop of such bodies
appeared within the course of the next few hours. This is merely
an illustration of the fact that the development is regularly
limited to the period between dawn and noon or at latest 1 p.m.
If sporangia have not appeared by the latter hour they will not
appear until the following morning. At first sight it appeared
not improbable that light-conditions were the determinent of this
phenomencn, but experiments proved that this was not so, for
the development followed the same course even where all light
was carefully and absolutely excluded.
The sporangia and spores described above are such as occur
by far most regularly and may be regarded as the typical form
of reproductive bodies in the organism, but certain other spo-
rangial bodies occasionally accompany or replace them, which
although differing in various particulars are, I believe, mere
aberrant varieties determined by the coincidence of special con-
ditions. In the first place, in place of those containing normal
spores, only varying within the limits as to size and form
ordinarily encountered, we also meet with sporangia which, in
addition to normal spores, contain a greater or less proportion
of irregular, unformed looking bodies (Fig. 20).
Fic. 20.—Abnormal forms of spores X 1000.
These, as a rule, are of larger size than the others, but are
_ connected with them by a series of intermediate forms, and
exhibit a precisely similar series of developmental changes in
passing into a state of activity. Sporangia in which such bodies
abound are frequently of an irregular form, and in some cases
may assume a dendritic character, appearing in branched tufts
which may attain a height of 1:5 mm. and a breadth of 2 mm.
(Pl. XVIII, figs. 4, 5); in other cases either in association with
these ill-formed spores or in normal sporangia, isolated encysted
Amoebe may be present, or bodies which resemble the frame-
work of an Ameeba containing sporoid bodies,
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 273
There is, however, a much more remarkable form of sporan-
gium which appears to be interchangeable with the common one,
sometimes almost entirely replacing it, sometimes occurring in
various proportions along with it, and sometimes appearing in
curious intermediate forms which combine the characters of both
varieties in one and the same individual. The first occasion
on which they were observed was in an artificial cultivation,
consisting of a portion of recent, freshly boiled cow dung into
which a normal sporangium from a previous cultivation had
been introduced. Forty-eight hours after the cultivation had
been set, the surface was found to be covered by a sprinkling of
very minute hyaline sporangoid bodies situated on the projecting
points of the medium. ‘These on microscopic examination were
found to consist of aggregations of large Amcbe which in
general were still readily separable and capable of resuming
independent activity in the nutritive fiuid into which they were
introduced. On the following day the sporangia had increased
in size and numbers, some of them being of a pearly-white
colour, others pale yellow, and others of a bright warm Indian
yellow. The white ones consisted of amcebal aggregates like
those observed on the previous day; the pale yellow ones con-
tained similar bodies, and a certain proportion of masses of
minute oval or broadly fusiform cellules (Pl. XVIII, fig. 14) ;
the Indian yellow sporangia contained enormous accumulations
of such cellules and a few large Amcebee. The sporangial mem-
brane was very distinctly defined in some cases, and on its
rupture masses of the cellules (Pl. X VIII, fig. 12) and large dis-
tinct Aicebze were forced out into the fluid of the preparation.
The cellules were, as before mentioned, broadly fusiform or oval
in outline (Pl. XVIII, fig. 13 4). They were flattened, colour-
less, and contained a large refractive and apparently oily nucleolus
of greenish yellow colour with a brillant shining nucleolus
within it. ‘I'he cells measured on an average about 6°2 x 3°7 pn,
and their oily nuclei 1°8 x 0°9 u. ‘In most cases when they first
escaped from the sporangia they were aggregated into small
lumps or groups by means of a gelatinous and very faintly
molecular basis-substance which soon dissolved and disappeared
in the nutritive fluid (PI. XVIII, fig. 18 a).
The presence of sporangia containing similar cellules was
recognised on several subsequent occasions. ‘The sporangia in
these cases varied in colour from clear pale yellow to full bright
vermilion, a phenomenon dependent partly on the proportion of
cellules present in them in relation to Amcebe or normal spores,
and partly on the proportion of oily matter around the nucleoli.
In some cases this was hardly represented, in others it formed a
large full-coloured globule, and in these the colour of. the
274 D. D. CUNNINGHAM,
sporange was always highly developed. In some cases curious
particoloured or piebald sporangia were present in which local-
ised portions of the contents consisted respectively of cellules and
of normal spores. The size of the cellules varied considerably
in different instances, ranging from that previously given down-
wards to specimens measuring ouly 3 or 4X2°7u; on other
occasions in which there was no microscopic evidence of their
presence, isolated masses of them were encountered among the
Amcebe and sporoids within normal sporangia or in those in
which only an imperfect spore-formation had taken place.
When the masses of cellules are allowed to remain in a suit-
able nutritive fluid, the gelatinous investing substance in which
they are embedded gradually dissolves and disappears leaving
the individual cells free. These now show a slight gradual
increase in size, the oily matter of the nucleus gradually dis-
appears leaving the greenish nucleolar particle very conspicuous,
and a minute contractile vesicle generally appears. The outline
of the cell also becomes somewhat modified, for while one
extremity retains its original pointed character, the other be-
comes somewhat rounded. Subsequently one or more flagellar
filaments are protruded from the latter, and the body swims off
as an active pear-shaped nucleated zoospore of minute size.
The zoospores after continuing their active movements for some
time, and in doing so frequently exhibiting very extensive ame-
boid changes of form, gradually cease to move, becoming at the
same time more or less rounded, and finally creep off as minute
Ameebee (PI. XVIII, fig. 16 a, 4, ¢, e, 7). Both zoospores and
Amcebe generally show the nucleolar particle originally present
very distinctly. In other cases the flagellated zoosporic stage
seems to be omitted and the cells, after undergoing a certain
amount of increase in size, pass off at once as nucleated Amebe.
In one or two instances I have met with large active Ameebze
containing varying numbers of these cells within them, but
whether this were a case of ingestion or of commencing develop-
ment, could not be ascertained (Fig. 21). These cells certainly
Fic, 21.—Large Amcba containing a mass of fusiform spores x 1000.
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 275
appear to resemble very closely, if not to be identical with those
described by Cienkowski under the name of Diplophrys ster-
corea, as forming sporangioid aggregations on specimens of
moist horse dung.! According to him, however, the sporangia
were devoid of any investing membrane or matrix, both of
which are unequivocally present in the present instance. The
characters of the movements in the cells when in the active
state is moreover different, and there does not seem to be any
tendency to the formation of compound groups by adhesion of
active cells as described by Cienkowski. Certainly, too, the
cells here are unprovided with anything of the nature of a shell
or differentiated external investing coat, which is regarded as
probably present in Diplophrys.
Taking the facts that they are so closely related to the
ordinary Amcebe and spores of the media in which they occur;
that they are included in many cases within the same sporangia
with these bodies; that they appear to be developed in groups
such as would naturally result from processes of division in
Ameebeze, and that in the active state they present characters so
similar to those of the zoospores and Ameebule developed from
the spores of the common form of sporangia, I am inclined to
regard these cells as merely a variety of reproductive bodies
belonging to the same organism, and not as the representatives
of a distinct species.
—— —_—_—_—_——.
I11.—Development of Excretal Parasites in Abnormal Media.
While in the excreta of cows and horses we find media which
permit of the continued vitality and further development of the
parasitic organisms which they contain whilst still within the
body, it must not be supposed that they are peculiar in doing
so. The excreta form the normal site for the reproduction of
continuous series of generations external to the body, but other
animal fluids apparently may more or less replace them in this
respect. With regard to one at all events—blood—there can
be no doubt. In comparing the appearances presented by the
biconcave spores of normal sporangia with those of blood-cor-
puscles, it was accidentally ascertained that the spores in place
of being destroyed by their transfer to the abnormal medium,
appeared to find in it the conditions for further development. . A
series of special cultivations in isolated wax-cells was therefore
carried out with the following results. When a drop of normal
blood suspended from a cover-glass is sealed in a wax-cell,
1 “Ueber einige Rhizopoden und verwandte Organismen,” ‘ Archiv fiir
mikrosk, Anat.,’ Bd, xii, S. 44.
276 D. D. CUNNINGHAM.
coagulation rapidly sets in, and with the contraction of the clot
a clear peripheral ring of serum is generally formed into which
white corpuscles emerge in varying numbers, retaining their
activity for various periods up to twenty-four hours. In about
four days the rouleaux have entirely broken up, leaving the cor-
puscles loose in the fluid. At the close of a period of a week
the serous ring begins to become stained by the solution of the
hemoglobin, and shortly afterwards the colour of the central
portion of the preparation begins to lose its brilliant scarlet
and to acquire a carbuncle red hue. ‘his change in colour
becomes more pronounced, and as the staining of the peripheral
vortion advances, the entire drop assumes a uniform deep ruby
colour. With the solution of the coagulum the white corpuscles
which have been entangled in it, as well as those in the peri-
pheral area which have not disintegrated, come conspicuously
into view, appearing as shining, white, oily-looking globules
among the surrounding deep red fluid; after this no further
change occurs, and the preparation remains seemingly unaltered
for months.
The phenomena in cases where a sporangium or spores have
been introduced into the drop are very different. The following
are the notes recorded regarding one set of experiments :—A
drop of blood was inoculated with a couple of normal sporangia
from a cultivation of cow dung, and sealed in a wax-cell. For
some hours the specimen exhibited similar appearances to those
of a pure blood specimen set at the same time for comparison ;
clear serum being freely expressed to form a peripheral zone into
which white corpuscles emerged, and the colour of the clot
remaining bright scarlet. Subsequently, however, a dark zone
appeared around each of the sporangia, indicative of local deoxi-
dation, a phenomenon frequently observed in ordinary slide
preparations of sporangia in blood. On the following morning,
twenty hours after the commencement of the experiment, the
clot was of a dirty brownish colour and the serum was deeply
stained. It contained an abundance of active, freely crawling
amceboid bodies which, had it not been for the altered condition
of the fluid and the fact of the sporangial inoculation, might
have readily been taken for persistently active white blood-cor-
puscles, as in size, general appearance, and character of move-
ment they were indistinguishable from such bodies. On the
next day the clot and seram were somewhat darker coloured.
The latter was full of active and still amceboid bodies of various
sizes; some when spherical measuring from 12 to 15 m in
diameter. As a rule, they showed a single well-defined nucleolar
particle, and some contained a pair of such bodies. ‘They showed
no signs of possessing a contractile vesicle, Some of them, in
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 277
addition to the ordinary scattered granules, contained a more or
less altered red blood-corpuscle in their interior. An abun-
dance of still molecular matter was also present in the serum,
but no active bacteria could be detected. On the next day the
serum was full of circular cells, either motionless or still ex-
hibiting slow form-change, while a few continued to progress
slowly. The average diameter of the circular cells was about 15 pu,
some of them contained three nucleoli. ‘They appeared as bright,
white, shining bodies in the yellow-stained serum. ‘Their pro-
toplasmic contents in some cases were aggregated into a central
or lateral granular mass, leaving the rest of the body apparently
occupied by a homogeneous fluid; a few much larger bodies
were present, attaining in some cases a diameter of 45, and of
an even molecular substance. The still, amcebal bodies com-
pletely filled the fieldin many parts of the preparation, especially
an the margins of the clot, were they formed continuous sheets
and masses. A fresh drop of blood was now taken, inoculated
from the previous one and sealed like it ina wax-cell. The initial
phenomena in this were just those characteristic of normal blood.
‘Twenty-four hours later, however, the clot had become of a dark
red-brown colour, and the serum contained much molecular
matter and numerous slowly moving amceboid bodies. On the
subsequent day, the latter were again observed, the activity of
movement being now more decided. ‘They contained a dim
nucleolus within a clear nuclear area, but were devoid of any
contractile vesicle. Twenty-four hours later the serum was full
of small Amcebe, measuring ahout 10m in diameter when cir-
cular, and provided with a distinct nucleolus. After another
interval of twenty-four hours the clot was found to be almost
everywhere surrounded by a bank of circular and slowly moving
binucleolate Amcebe, measuriag when at rest about l5y in
diameter, and appearing as bright punched-out areas in the
brownish serum.
A second transfer was now made as before, inoculation being
effected by means of a needle which had, as formerly, been
heated to redness, and allowed to cool immediately previous to
the operation. In this case the results were of a similar nature
to those in the previous experiment; only the appearance of the
Ameebe was somewhat retarded. Ultimately an enormous accu-
mulation of still amceboid cells was formed as before. A third
transfer was next carried out, but was followed by no develop-
ment of Amcebe, the basis merely rapidly breaking up and be-
coming full of molecular matter. The experiments as they stand,
however, clearly show that the spores of the organism, although
finding their natural medium in excretal matters, are perfectly
capable of life and activity in other media. In some of the
278 D. De CUNNINGHAM,
series of blood cultivations there certainly appeared to be a cer-
tain amount of spore formation, as subsequent to the appearance
and cessation of activity in the Amcebe, masses of much smaller
spheres made their appearance among the amebal aggregates, the
individual cells of which measured from 4 to 6 » in diameter.
As no process of multiplication by division during activity was
ever observed to take place, and as, at the same time, no evident
diminution in the numbers of bodies developed in successive
inoculations manifested itself, it seems, indeed, probable that the
occurrence is a normal one. Cell cultivations in which boiled
milk was substituted for blood failed to show any similar phe-
nomena, the intense acidity developed in the medium subsequent
to inoculation seeming to be fatal to the spores.
Numerous attempts were made to cultivate the sporangial
spores and Amcebz of cow dung in human excreta, but at first
without any result. Like the similar bodies naturally present in
the medium, they invariably appeared to be killed by the stage
of acid fermentation. Even where the development of acidity
was very limited, as in cases where the occurrence of Oidium
was prevented by prolonged boiling, it was long before any posi-
tive results were obtained in dealing with fresh excretal matter,
and the investigation had almost been given up, when, due to an
accidental case of inoculation, it was ascertained that the case is
very different when the medium has once entered on the alkaline
stage of fermentation. Here, in place of being unfavorable to
the vitality of the organism, the material appears rather to be
specially adapted to it in some respects, although, at the same
time, the normal cycle of developmental phenomena characterising
it in its natural medium fails to occur with constancy. There
is not the same strong tendency to the formation of regular
sporangia, and the individual ameboid elements tend rather to
retain an independent existence, attaining at the same time an
abnormal magnitude ; sporangial formation, however, is not always
absent, although in most cases in which it occurs assuming an
abnormal character.
The history of a case in which an imperfect development of
sporangia occurred is as follows :—A portion of perfectly fresh
normal human excreta was boiled for half an hour, and then set
in a moist chamber. The material was almost neutral, and con-
tained the usual microscopic constituents—dééris of various
sorts, an enormous accumulation of still bacterial matter, and a
sprinkling of still circular Amcebe possessing one or two distinct
nucleolar particles. On the following day the material was
unaltered in appearance. Its reaction was decidedly and per-
manently acid, and all the bacteria were still. Twenty-four hours
later the acidity was less pronounced ; at the close of forty-eight
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 279
hours it had been replaced by strong alkalinity. ‘The surface of
the material was now covered with a creamy greyish-yellow layer
of bacteria, which at once began to move actively in nutritive
fluid. On the following day it was inoculated with one or two
normal sporangia from a dried cultivation of cow dung, the
condition of the sporangia being specially favorable to their ready
transfer. Two days later the cultivation was again examined.
The basis retained its highly alkaline reaction, but the bacterial
rods had now been almost entirely reduced to series of spores
(Fig. 3), so that the surface coating consisted of little save dense
masses of brightly refractive granules. Inthe gelatinous matter
of this coating numerous large Amebe were slowly crawling
about. None of them at this time showed a contractile vesicle,
but the majority possessed a distinct clear nuclear area contain-
ing two disc-shaped greenish nucleoli. In some cases the denser
portion of the body was crowded with an amorphous mass of
granules, and in others similar granules were aggregated into
spheres contained in fluid vacuoles (Fig. 22). In appearance
Fic, 22.—Large Ameeba with digestive vacuoles x 1000.
and measurements the granules within the Amcebz were identical
with the bacterial spores of the medium. The Amebze precisely
resembled those frequently encountered in fresh human excreta,
but in size considerably exceeded those normally developed in
cow dung cultivations.
On the following day the cultivation was found to be crowded
with huge active Amcebz, like those of the previous day. When
first introduced into the nutritive fluid of the preparations they
presented a peculiar tuberculate or irregularly cornuate outline,
but they rapidly unfolded and crawled freely about. Their
nucleoli varied greatly in size; in some cases the discs attained
a diameter of 5°5 uw. Specimens of Amceebe which had been re-
served beneath a cover-glass had passed into the condition of
280 bD. D. CUNNINGHAM.
dilatation and rigidity normal under such circumstances. They
were circular, entirely or almost entirely motionless, the granular
matter which they contained gathered into hard lumpy masses,
and with a large sharply-defined clear vacuole, apparently a rigid
contractile vesicle. Some of them showed a very instructive
phenomenon. In such specimens vacuolar cavities containing
spherical masses of bacterial spores were still present. The re-
markable thing in reference to these was that in many instances
a development of a new generation of active bacteria had occurred
within them, active rods darting hither and thither in the peri-
pheral fluid of the vacuoles, and knocking and turning about the
persisting granular mass (Fig. 23), Interpreted in accordance
Fic. 23. Development of Bacteria within digestive vacuoles of dying
Ameba x 1000.
with current theories of disease, this phenomenon would indicate
that the Amcebe were dying, due to their infection with bacterial
organisms ; whereas, in fact, there can be no doubt that the
presence of the latter was really the result of processes of de-
velopment in the ingested spores occurring after the Amcebee had
been enfeebled or killed by the supervention of unfavorable con-
ditions in the medium. ‘The Amcebz, as usual, were apparently
slowly asphyxiated by insufficient access of air to the medium,
and the bacterial elements within them now underwent develup-
ment in place of digestion. They clearly had not invaded the
amcebal body subsequent to its death, being confined solely to
the digestive vacuoles of the interior, whilst the peripheral sub-
stance remained entirely free from them. Moreover, the Amebe,
in certain instances, appeared to be enfeebled rather than actually
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 281
dead, as faint changes in their form continued to manifest
themselves with more or less distinctness.
On the following day the cultivation continued to swarm with
huge Amcebe. The body-substance was denser and less trans-
parent than previously, and the nucleoli were very hard to dis-
tinguish, and in many cases indeed quite irrecognisable. In
some cases they had begun to form masses of epithelioid tissue
consisting of various numbers of more or less fused individuals.
The figure on a former page (Fig. 13), illustrative of conjugate
Ameebe, was taken from this cultivation, and shows an example
consisting of three individuals, each provided with a solitary
large rigid vacuole. The Amcebz in these masses were perfectly
motionless. ‘Twenty-four hours later the condition of the cul-
tivation remained much as before. In still, dilated Amcbe
which had passed into a condition of rigor in a preparation of
the previous day, the nucleus was in some instances very clearly
defined. It was here seen to form a distinct bilocular capsule,
which in the course of disintegration of the Amcebe to which it
belonged sometimes escaped entire into the fluid of the prepara-
tion (Pl. XVIII, fig. 15). Hach of the cavities contained one
sometimes two greenish discoid nucleoli of varying size. On
the next day isolated and aggregate Amcebe continued to be
present in extreme abundance in the cultivation. They were now
almost all characterised by the extreme indistinctness and very
small size of their nucleoli, so that these bodies m many cases
could not be detected even when specially sought for.
Two days later the aggregations of still Amcebe had become
so large in many cases as to form distinct irregular whitish
masses visible to the unaided eye on the surface of the medium,
and in many of. these there were considerable numbers of
smaller sporoid cells. Some of the large Amcebe were in the
flattened scale-like condition, and here the nucleus was almost
or entirely invisible. A large, slowly acting contractile vesicle
was, however, frequently present, which generally was formed
by the fusion of several originally independent vacuoles which
underwent fusion as they expanded. Some of the large ad-
herent Amcebe measured as much as40 x 37°5 uw and upwards.
The sporangioid bodies continued to increase in numbers and
size, and in the course of the next three days were entirely con-
verted into masses of spores, hardly a single large Amebe
remaining recognisable. The spores were somewhat larger, as a
rule, than those ordinarily present in the normal sporangia
developed on cow dung, but they varied considerably in size
in individual instances, ranging from 5 to 10 w in diameter.
Shortly after the sporangial masses were introduced into nutri-
tive fluid, zoospores began to emerge from them. Most of
VOL, XXI.—NEW SER. T
282 D. D. CUNNINGHAM.
these were of large size corresponding with that of the spores.
They swam about actively in the fluid, and in many instances
exhibited very free amceboid changes of form while doing so.
In all their characters they were quite indistinguishable from
similar bodies as encountered in fresh human excreta, and like
them were frequently observed to multiply by division. Due to
this and to the constant emergence of new individuals, the pre-
paration in the course of a few hours was swarming with active
zoospores. At this time a certain number of small active ame-
boid bodies was also present, which seemed in most cases to
emerge directly from some of the larger spores. The prepara-
tion was reserved and again examined on the following day.
The margins of the fluid still swarmed with active zoospores,
some of them of very large size, but otherwise agreeing with
their compeers in every respect. In many of them a contrac-
tile vesicle was clearly visible. Their movements varied greatly
from time to time, free swimming being alternated with caudal
adhesion, or with a crawling motion accomplished by means of
ameeboid protrusions of the body-substance.
The cultivation after this appeared to remain unchanged, no
further development occurring, and the surface continuing
covered with a thick layer of bacillar spores and of spore-cells
derived from the Ameebe. It remained throughout entirely free
of any fungal mycelium.
In the majority of similar cultivations the results closely
resembled those just described, but in one case, at all events, a
development of well-formed normal sporangia took place, and in
others various deviations in the form of arrested development
occurred. The series, taken as a whole, appeared unequivocally
to prove the identity of the organisms occurring in human and
vaccine excreta, and also that the zoospores are merely a form
which the reproductive bodies resulting from processes of divi-
sion in the Amcbe may assume, interchangeably with the
common amebal form directly developed in cultivations of
sporangia in cow dung. In showing this they also afforded a
ready explanation of the extreme frequency of the parasite in
the human subject, for they indicated the presence of a constant
source of readily transferable reproductive elements.
IV.—Relation of the Excretal Parasites of the Lower Animals
to those of the Human Subject.
We have already seen that the vaccine excreta furnish the
conditions for the continued existence and repeated reproductive
multiplication of the parasites external to the host-body, crops of
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 283
sporangia being apparently indefinitely produced so long as the
spore-cells obtain access to the medium while in a recent state,
if certain conditions of temperature and moisture be provided.
Further, we have ascertained that the reproductive elements are
capable of retaining their vitality for prolonged periods when in
a dry state, and that they are then also capable of resisting
influences which are fatal to them in activity, so that a constant
supply is always at hand for introduction. These may of
course obtain access to the body by various means. The
transfer in the case of cattle probably occurs by means of
fodder in which the sporangia are constantly liable to be
present. In the case of the human subject it, no doubt, occurs
in various ways, the great means of diffusion in all probability
being the air. That the air is the chief agent by which the
reproductive elements are diffused appears probable for several
reasons. ‘There can be no doubt as to the constant entrance
of the reproductive bodies into the air, both as isolated spores
and entire sporangia. The sporangia, when thoroughly dried
are detached by the slightest contact from their points of attach-
ment, and having been so, are so light as readily to be carried
about by air-currents. One of the difficulties encountered in
the study of dried sporangia is, in fact, dependent on their
extreme lightness and the ease with which they are swept away
by the air. This is not all, however; it is not only evident
that a possibility for constantly recurring diffusion of the
reproductive bodies by means of the air exists, but it also
appears probable that when thus diffused they are more likely
to undergo subsequent development than when diffused by the
only other medium which can be supposed to play an influential
part in the process—water. The more thoroughly dessicated
the sporangia and spores are, the more are they capable of
retaining their vitality under exposure to unfavorable con-
ditions. When active, or when without being so, they have
become softened and distended by immersion in passive fluids,
they readily suecumb to influences which, when dried, they are
capable of resisting with impunity for considerable periods.
Now, there appears to be little reason to doubt that in the acid
gastric fluids we have such unfavorable media, likely to act
prejudicially on the reproductive bodies entering the digestive
canal unless specially protected. Active or softened elements
will thus probably fail to reach a locality favouring their further
development, while those in a desiccated condition will pass on
unaffected to assume activity in the lower portions of the
digestive tube.
In so far as the observations here recorded justify us in
coming to a conclusion, the development of the parasite appears,
284 D. D. CUNNINGHAM.
as a rule, to follow a somewhat different, course according as it
takes place within or without a host-body. In media external
to the body the spore-cells generally give direct origin to
Ameebule, which in their turn produce a new generation of
sporangia. Now, certainly, any true sporangial formation never
occurs within the body, indeed, it is scarcely possible that it
should occur seeing that the constant movements of the medium
must mechanically tend to prevent the initial aggregation of the
formative units. It is notso easy to determine to what extent any
new spore formation takes place at all, or how far the entering
spores normally assume an amoeboid condition on emergence, or
whether the zoosporic condition replaces the amceboid one as it
does in certain cases external to the body. That they sometimes
do give origin to Ameebze, and that the latter, although failing
to produce sporangia, may, in some cases, develop a new
generation of reproductive elements, seems to be clear; but it
remains undetermined how far this is a normal event. The
question is, does an amceboid stage normally intervene between
the entering spore and the zoosporic elements abounding in the
lower portion of the intestinal tube? In other words, are the
zoospores there the products of spores developed in Amebe
derived. from the extraneous reproductive elements, or are they
directly derived from the latter? is the flagellate zoospore the
normal form assumed by the reproductive elements within the
body as the Ameeba is external to it? This is a question which
cannot, in the meantime, be definitely answered. There seems
to be no doubt that zoospores, in certain circumstances, are
developed as the normal product of the intra-intestinal Amebe ;
but this of course does not exclude the possibility of their
coincident development from extraneous spores also.
It now remains to consider the relation which the presence of
the parasite bears to cholera and other morbid conditions with
which it appears to be specially associated. It may be asked
why any special association should occur if the reproductive
elements of the organism are so generally diffused and so con-
stantly liable to be introduced into the digestive tube as they
appear to be. The answer to this question appears to be as
follows :—The special prevalence of the parasite in the excreta
in cholera and other intestinal disorders seems to be determined
by the abnormal characters of the intestinal contents.
With regard to this point it may be sufficient to recall the
fact that the alkaline choleraic fluids may be readily demon-
strated to be an efficient nutritive medium—a medium much
more favorable to the parasite than the material of normal
excreta is. They have frequently been employed as such in the
study of the parasite as present in normal excreta, and again
4
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 285
and again it has been observed that elements which in their
natural medium were in an inactive and seemingly dying con-
dition were rapidly roused to activity and multiplication under
their influence. Leaving the chances of excessive or repeated
introduction of extraneous reproductive elements entirely out of
account, the rapidity with which multiplication by division may
occur, under favorable circumstances, appears to be amply suffi-
cient to account even for the excessive multitudes of zoospores
present in certain specimens of choleraic excreta. As a matter
of observation, it is undoubted that processes of division may
recur at a rate of two per hour in the same zoospore, and a
calculation of the numbers which may thus be developed under
favorable circumstances, even within comparatively brief periods,
renders it evident that the numbers of parasitic elements present,
even where most excessive, do not necessitate the conclusion
that the parent bodies originally introduced must have been very
numerous.
Experiments on the artificial introduction of the sporangia
into the bodies of healthy animals have never been followed by
any special result. I have again and again caused a dog to
swallow large numbers of sporangia in all stages of develop-
ment and desiccation without the treatment producing the
slightest appreciable effect, and on one occasion introduced a
solution crowded with spores into the peritoneal cavity of a
guinea pig with as little result. The presence of morbid con-
ditions certainly determines the degree of development of the
parasite, but the presence of the latter seems to be incapable of
giving rise to disease. The result of these experiments is sug-
gestive, inasmuch as it shows how closely parasitic organisms may
be associated with disease without being causally related to it.
In many cases in which experiments have been supposed to
demonstrate the essential dependence of disease on parasitic
organisms, the procedure has not, as in the present case, con-
sisted in the introduction of these organisms per se, but in the
introduction of morbid fluids or other materials containing them.
For example, we find Lésch affirming the essential causation of
certain dysenteric conditions to lie in the presence of his Amada
coli, beeause in one instance where he injected dysenteric excreta
containing the parasite into the rectum of a dog, dysenteric
lesions and a development of the parasite ensued. Now, there
can be doubt that if in the present series of experiments morbid
fluids containing the parasite had been employed in place of
clean specimens of sporangia and spores, the results might have
been very different. If a solution of choleraic or normal ex-
creta containing the parasite had been substituted for the solution
of the spores per se, in the experiment on the guinea pig, it may
286 D. D. CUNNINGHAM,
safely be affirmed that septicemia leading to a fatal result would
have followed; and it is very probable that had the parasitic
elements in the excretal solution consisted of dried or encysted
spores, we should have had a coincident development of the
parasite parallel to that occurring in the blood cultivations pre-
viously described. Had this been so we should, following a line
of argument similar that adopted in reference to the relation of
Ameba coli to dysentery, have been led to conclude that the
parasite was the cause of death.
The phenomena presented by the parasite whose life-history
forms the subject of the foregoing pages, in the various stages
of its development, render it somewhat difficult to determine to
what group of organisms we ought properly to refer it. Inany
attempt at doing so, the question of its animal or vegetal nature
need not occupy us, as it appears certainly to belong to that
series of organisms which in the mean time, at all events, must
be included in the Protista, the intermediate kingdom to which
all doubtful organisms wanting in differentiated animal or vegetal
characters are conveniently referred. There are two groups in
this no-man’s-land to which it shows certain points of affinity,
appearing in some respects, indeed, to occupy an intermediate
position between them. ‘These are the Monadine, as they are
termed by Cienkowski, or the Protomonadina, as they have been
subsequently named by Heckel, and the Myxomycetes, which are
by some still regarded as an order of fungi. It appears to be
related to the Monadina in the absence of any definite plasmodial
stage interposed between the zoosporic and the sporangial one,
and in the fact that individual units developed from single spores
appear occasionally to proceed to spore formation. On the
other hand, the complex nature of the sporangia, which are de-
veloped as the result of the close association and more or less
complete fusion of distinct zoosporic elements, points to a close
affinity to the Myxomycetes. In some cases, indeed, the fusion
of the formative elements advances so far as practically to be
equivalent to plasmodial formation, but the occurrence of such
a phenomenon cannot be regarded as normal, the spores, as a
rule, being developed in groups corresponding to individual
units, and the fusion in any case being immediately antecedent
to spore formation. In characters, too, the sporangia closely
resemble those in certain forms of Myxomycetes. The organic
granules developed in the walls closely resemble those charac-
terising some myxomycete sporangia, and the ridging or reti-
culation of the inner surface of the membrane and the rudi-
mentary capillitium clearly correspond to myxomycete structures.
Taking all its characters into consideration, the organism appears
rather to represent a rudimentary form of the myxomycete group,
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 287
and it may, therefore, be conveniently distinguished by the name
of Protomyxomyces coprinarius.
It has already been pointed out that the different develop-
mental forms of the parasite exhibit a high degree of variability
under the influence of variations in the external conditions to
which they areexposed. Various forms of the zoospores are thus
encountered, replacing one another in different media and in the
same medium at different times. In some cases the flagellate
zoospores show a distinct contractile vesicle and nucleolar point ;
in others any differentiation of such structures seems to be want-
ing. The degree and character of movement, the consistence,
size, and outline of the body are also extremely inconstant ; and
a similar variability, although perhaps to a somewhat slighter
extent, prevails in the ameeboid stage. There is one very distinct
form of the flagellate zoospores which in many respects is so un-
like the common ones that it might readily be regarded as an
indication of specific difference, were it not possible to observe
its origin as a mere transition form. In this case the body is
characterised by a peculiar spathulate flattened contour, and ex-
hibits a peculiar type of movement, consisting in a hinge-like
flexion of the posterior slender portion of the body on the an-
terior broader part. In some specimens of choleraic excreta, as
was previously pointed out,! this variety almost entirely replaces
the normal one, but its occurrence is not limited to such media,
as it has more than once been observed to arise in cultivations
of cow dung. Variation in the size of the spores in the same
or in different sporangia is a phenomenon of constant occur-
rence, and one which runs through a wide range of develop-
ment. As we have previously seen, moreover, there is some
reason to believe that there are two distinct forms of spores,
which may replace one another more or less completely under
different circumstances, the commoner one being distinguished
by its spherical or biconcave figure, the other by its smaller
size, more or less fusiform outline, and well-marked nucleation.
So far as I have been able to ascertain, the occurrence within
the digestive canal of the human subject in this part of India of
zoospores or ameeboid bodies belonging to any other develop-
mental cycle than that which has been described above is very
rare and quite exceptional. It is different, however, in the case
of other animals in which the same parasitic forms occur. In
many specimens of fresh vaccine excreta smaller numbers of
various other organisms are also occasionally present. Some of
these are unquestionably specifically distinct, and others, while
not unequivocally so, still present certain characters requiring
? *Seventh Annual Report of the Sanitary Commissioner with the Go.
vernment of India,’ Appendix B, p: 189.
288 D. D. CUNNINGHAM.
that they should in the meantime be kept apart. Of the former
class of bodies one of the most frequently present is apparently
a species of Chlamydophrys, Cien.,! while as representatives of
the latter we have various zoosporic forms characterised by the
possession of a differentiated cell-wall, and by the fact that in
the process of multiplication the line of division is longitudinal
and not transverse to the original long axis of the body,.-
and starts from the point of emergence of the flagellum
(Fig. 24).
Fie. 24.—Maultiplication of Zoospores by longitudinal division x 1000.
Another characteristic organism, occasionally present in con-
siderable numbers, appears in the form of peculiar, somewhat
erescentic, colourless cells, which closely resemble certain
fungal conidia, and are frequently aggregated in linear series
(Fig. 25).
Fie. 25.—Fusiform cells from cow dung x 1000.
In some cases, too, a peculiar form of sporangioid structures
makes its appearance either on the same basis with the charac-
teristic sporangia, or apparently replacing them. In colour they
vary considerably, in some cases being pale buff, in others
salmon-coloured, and in others orange or red. ‘They are always
of relatively small size, of irregular outline, and unprovided with
a pedicle (Fig. 26).
Their texture is firm, and they have a more or less distinctly
1 “Ueber einige Rhizopoden und verwandte Organismen,’ ‘ Archiv fiir
mikrosk. Anat.,’ Bd, xii, s. 39,
MICROSCOPIC ORGANISMS IN INTESTINAL CANAL. 289
defined capsule. Within this, as a rule, we find a thin layer of
granular matter surrounding a dense mass of minute circular
Fic, 26.—A, Sporangoid mass x 44. B, Sporules x 1000.
sporoid bodies measuring about 1°8 « in diameter. The develop-
ment of these sporangia has not been followed out, so that their
true nature remains uncertain.
The principal conclusions which seem to be warranted as the
result of these investigations have been already stated in the
course of the narrative, but in concluding, it may be well to
bring them together into a continuous series. They are as
follows :
1. Special parasitic forms may be specially associated with
particular forms of disease without holding any causal relation
to them.
2. The monadic, amcebal and sporoid bodies, so abundant in
many choleraic excreta, are all developmental forms of one
species of parasite which I propose to call Protomyxomyces
coprinarius.
3. This parasite appears to be closely related to the organisms
included within the Protist groups of Protomonadine and
Myxomycetes, and in certain respects seems to represent a con-
necting link between them.
4. It is not confined to choleraic or even to human excreta
as a basis, and only attains its full development external to the
bodies of the animals within which it occurs.
5. Its immature forms occur parasitieally as normal inmates
of the digestive canal in certain of the lower animals.
6. In the human subject, both in health and disease, they are
very frequently present in varying numbers.
7. During health the number and activity are limited, due
to repressive influences exerted by the normal intestinal con-
tents as a medium.
8, Their excessive abundance in certain forms of disease is
290 D. D, CUNNINGHAM.
due to abnormal conditions of the intestinal contents, permitting
of the occurrence of processes of rapid multiplication.
9, Normal human excreta do not form a medium in which any
farther development of the parasitic elements outside the host-
body can occur.
10. On the contrary, the normal series of fermentative changes
through which the excreta pass after exit from the body ensures
the complete destruction of the parasitic elements.
11. No such destructive effect, however, is exerted by the
changes occurring during the decomposition of the excreta in
certain lower animals —specially cows and horses; and here the
parasitic elements on their escape from the body undergo farther
processes of development resulting in the production of repro-
ductive bodies securing the continuance and diffusion of the
species.
12. Such excretal matters, therefore, serve as a constant
source whence parasitic elements may be transferred to the
bodies of other animals.
13. Human excreta which have passed through the initial
processes of decomposition, and which have thus become alka-
line, allow of the continued existence and multiplication of
elements of the parasite which may then obtain access to them,
and may thus serve as a second centre of reproduction.
14. The introduction of the reproductive elements of the
parasite into the human body is mainly effected through the
medium of the air.
15. The introduction of the reproductive elements per se
seems to be quite innocuous.
16. The special association of the parasite with intestinal
disorders appears to be dependent on the abnormal condition of
the intestinal contents allowing of the rapid multiplication of
reproductive elements which may obtain access to them.
Catcutta ; November, 1879.
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS, 29]
REsFARCHES upon the DEVELOPMENT of STarcH-GRAINS.
By A. F. W. Scuimper. (Pl. XIX.)!
1. Tue formation of starch-grains in chlorophyll-corpus-
cles was investigated first by Nageli® and then by Sachs,?
and the conclusions arrived at were the same in both cases.
Both observers directed their attention principally to the
leaves of flowering plants, but Nageli further observed the
green ground-tissue of the stems of certain Cacti and also
the Characez. According to their accounts, which are essen-
tially the same, the starch-grains are formed, either singly or
several together, at various points in the chlorophyll-corpus-
cles; they then increase in size, and where several are
present, they become flattened along the planes of contact.
The chlorophyll-corpuscle also increases in size at first, but
it subsequently diminishes, and it frequently disappears more
or less completely.
Ican confirm the results of these observers as regards the
material which they used. This mode of the formation of
starch appears to be universal in the mesophyll, and it
occurs also in the green portions of the stems of many, but
not of all phanerogamous plants. The mode of the formation
of starch-grains in the stems of some plants differs con-
siderably from that which has been described. In these
cases the starch-grains do not originate at any indefinite
points in the chlorophyll-corpuscles, but always just beneath
their free surface (figs. 4,6, 9). The thin layer of the chlo-
rophyll-corpuscle which covers the starch-grains is soon rup-
tured, and the grains then project. ‘They frequently appear
to be quite superficial from the beginning.
If the chlorophyll-corpuscles are spherical and not
flattened, starch-grains may originate at all points of the
peripheral portion. If, however, and this is more frequently
1 This paper was published in the ‘ Botanische Zeitung’ for 1880,
No. 52. The author had no opportunity of seeing the paper by Dehnecke
on a similar subject, which was published earlier in the year, ‘ Ueber
nicht assimilirende Chlorophyllkorner” (Diss. Inaug. Bonn.,’ 1880).
Dehnecke shows that starch-grains may be formed in chlorophyll-corpuscles
otherwise than by assimilation.
+ ‘Zeitsch. fiir wiss. Bot.,’ Heft iii u. iv; ‘ Die Starkekérner,’ p. 398.
> “Ueb. den Hinfluss des Lichtes auf die Bildung des Amylums in den
Chlorophyllkérnern,” ‘ Bot. re 1862; “Ueb. die Auflésung und
Wiederbildung des Amylums in den Chlorophyllkérnern bei wechselnder
eae eee ‘Bot, Zeitg.,” 1864; ‘ Experimental Physiologie,’
S. 3 .
292 A. F. W. SCHIMPER.
the case, the chlorophyll-corpuscle is discoid, the localisation
is greater,so that the formation of starch-grains, is confined to
the equatorial zone. Chlorophyll-corpuscles of this kind
often produce six or more starch-grains, which form a girdle
in this plane, whereas the central portion and the flat sur-
faces of the corpuscles are free from them (figs. 4 and 5) ;
occasionally a minute grain may be formed in the flat
surface.
These peculiarities in the mode of development of the
starch-grains from the chlorophyll-corpuscles, and in the
mode of their nutrition, are intimately connected with
certain peculiarities in their structure.
The starch-grains which originate in the interior of a
chlorophyll-corpuscle and remain enclosed within it, have
a concentric structure (for instance those formed in the
cortical and medullary parenchyma of certain Cacti, such
as Cereus speciosissimus) ; in most cases such starch-grains
remain very small and exhibit no differentiation. The
starch grains of Vanilla planifolia' (figs. 1—3), which
are of this kind, deserve special mention. When mature
they are spherical completely colourless compound grains,
consisting of hundreds of small similar polyhedral grains ;
they closely resemble those of the endosperm of the
Caryophyllez and of the tuber of Mirabilis Jalapa. An in-
vestigation of their development shows that the small grains
arise as minute points in the chlorophyll-corpuscles; they
then increase in size, and become polyhedral in consequence
of mutual pressure; the substance of the chlorophyll-cor-
puscle becomes gelatinous, decreases in size, and finally
disappears.
Those starch-grains which originate in the second way,
that is, in the peripheral portions of the chlorophyll-corpus-
cles, usually attain a much greater size. Those which occur
in the stems of Begonia, Peperomia (e.g. P. stenocarpa),
Pelargonium, Ozalis Ortgiesu, Dieffenbachia Seguina, Costus
Malortieanus, and less markedly those which are present in
the stem of the Potato, are among the largest and the most
perfectly developed ; they exhibit a very distinct differentia-
tion of hilum and layers. Such starch-grains are all eccen-
tric, and the side which has grown the most is, without
exception, the one to which the chlorophyll-corpuscle is
attached (figs. 8 a, 10 and 12). From this fact it clearly
follows that the unequal growth of the two sides of the
starch-grain is a consequence of an unequally distributed
a For this material I am indebted to the kindness of Prof, E. Morren of
iége,
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS. 293
nutrition. This conclusion is further supported by the fact
that when the starch-grains come into contact with other
chlorophyll-corpuscles, prominences are developed upon them
at the points of contact (Peperomia stenocarpa, fig. 8 ; Oxalis
Origtesii, Dieffenbachia Seguina, fig. 13).
The different stages in the development of the starch-
grains, in so far as they are related to the chlorophyll-cor-
puscles, are essentially the following :—The starch-grains
which are produced by flattened chlorophyll-corpuscles are
at first wedge-shaped and flattened in the same planes as
the chlorophyll-corpuscle ; the side which is connected with
the corpuscle is truncated, often somewhat concave or
uneven, whereas the free end is rounded. When the for-
mation of starch is very considerable, the chlorophyll-cor-
puscle gradually assumes a nearly isodiametric form ; it
diminishes in density, and subsequently also in size, until
only a small residue of it is left, or it may disappear
entirely. Simultaneously the starch-grain becomes thicker,
and usually acquires an ovoid form. The growth of the
starch-grain ceases with the disintegration of the chloro-
phyll-corpuscle. ‘The process of development can be easily
observed in Peperomia stenocarpa (figs. 6—8), and in Ozalis
Origiestz (figs. 9 and 10); for observing the first forma-
tion the cortex of Philodendron grandifolium (figs. 4 and
5) may be recommended. ‘The starch-grains which are
formed in chlorophyll-corpuscles which are not flattened,
are, so far as can be ascertained from the scanty observa-
tions, at first hemispherical, the flat surface being in contact
with the chlorophyll-corpuscle.
In those chlorophyll-corpuscles which are capable of
producing starch in all parts of their substance, the starch-
grains may of course be formed near the surface and may
sooner or later project freely. In this case, which is by no
means rare in the mesophyll (e.g. Tradescantia, Begonia,
&c.), the starch-grains must be excentric. I have, however,
not succeeded as yet in finding grains of this kind exhibit-
ing evident differentiation.
2. The observation of fresh sections, not too thin, of parts
of plants which do not contain chlorophyll, shows that the
starch-grains which are in process of development are not
surrounded by ordinary protoplasm, but that they are con-
ained in, or attached to, peculiar refrangible corpuscles
which are usually spherical or spindle-shaped. These
bodies are very unstable. So soon as the surrounding fluid
penetrates into the cell they swell up considerably and
then dissolve. Close observation has shown that prolonged
294 A. #, W. SCHIMPER.
treatment, for days or weeks, with alcohol, causes these cor-
puscles to become smaller and more resistant. This effect
is immediately produced when they are treated with a
watery iodine solution, and this is the best means for
examining them ; they then become stained of a darker or
lighter yellow colour, according to the concentration of the
iodine solution. Millon’s reagent colours them, when coa-
gulated, a brick red, and nitric acid colours them yellow.
These reactions indicate that the bodies in question consist
of albuminous substances.
The investigation of the earliest stages shows that these
corpuscles are present before the starch-grains, and that the
starch-grains which are subsequently produced bear the
same relation to these corpuscles as regards their develop-
ment as the starch-grains which are developed in assimilat-
ing cells do to the chlorophyll-corpuscles which are present
in those cells. The starch-grains may be produced at any
‘points within these corpuscles, or their formation may be
confined to the peripheral portion.
The starch-grains which are developed in the peripheral
portion of these albuminous corpuscles, and which therefore
have one side free at an early period, have an excentric struc-
ture, and the hilum lies near to the free end (figs. 19, 23,
36—40, 48), just as in the excentric starch-grains which
are produced by chlorophyll-corpuscles. If the starch-
grains come into contact with other of the corpuscles
prominences of various forms are developed upon them. In
the cases in which I have as yet investigated, the starch-
grains which had been developed in the interior of one
of these corpuscles were compound; the minute grains
composing them rarely exhibited any perceptible differen-
tiation, but when they did it was always concentric (figs.
24-29). These corpuscles, like the chlorophyll-corpuscles,
become larger at first after the formation of the starch-
grains, and this is usually accompanied by a diminished
refrangibility ; they then become smaller and gelatinous,
and finally they altogether disappear.
The behaviour of these bodies indicates that they are the
starch-forming organs in cells which do not assimilate, that
is, that the conversion into starch of the assimilated sub-
stances which have been conveyed from other parts of the
plant is effected by means of them.
In the cases in which a starch-grain is formed in the
interior of one of these corpuscles its function is obvious.
In those cases in which the starch-grain is formed in the
peripheral portion of the corpuscle, and soon projects freely
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS, 295
from it, the function of the corpuscle is indicated by the
constant connection of the starch-grain with it, and by the
fact that the portion of the grain which is in contact with it
is the part which has grown the most rapidly. If the cor-
puscle were not a starch-former, it would only hinder the
access to the starch-grain of plastic substances, and in that
case the growth of the side of the grain in contact with the
corpuscle would be less than that of the other.
I shall call these bodies in the following pages “ starch-
forming-corpuscles” (Starkebildner).
I will now give a short account of the development of
these corpuscles and of the starch-grains in a few plants.
One of the most appropriate objects for observations of this
kind is the epidermis of the stem and petiole of Phzlo-
dendron grandifolium (figs. 14, 15). In young cells the
nucleus, which is either parietal or suspended in the vacuole
by threads of protoplasm, is seen to be surrounded by a con-
siderable number of glistening spherical bodies, which much
resemble the nucleoli. The development of these bodies is
essentially the following:—The nucleus of a young cell is
surrounded by a layer of dense protoplasm, which is at first
uniformly thick, but which subsequently becomes uneven.
The prominences, which are at first hemispherical, round
themselves off to form the spherical bodies mentioned above,
whilst the intermediate substance assumes the properties of
ordinary protoplasm. This process is probably to be inter-
preted thus: that a substance which is at first uniformly
distributed in the protoplasm investing the nucleus separates
out, and collects around certain centres of attraction. These
spherical bodies behave with reagents in the manner described
above; they are the starch-forming-corpuscles. They de-
velope numerous starch-grains close beneath their surface,
which remain small, especially in the petiole, and often form
a hollow sphere surrounding the central portion of the cor-
puscle. In this central position it appears that no starch-
grains are formed. The duration of these starch-grains is
limited ; in the mature thick-walled cells of the stem
1 The vesicles containing starch (Brutblaschen), which were discovered
by Nageli (‘ Zeitsch. f. Wiss. Bot.,’ i, S. 149, iii, p. 109), are doubtless the
same as our starch-forming-corpuscles. Trécul (‘ Ann. d. Se. Nat.,’ sér. 4,
t. x, ‘ Des formations vesciculaires dans les cellules végetales ”) observed
and correctly drew these bodies in the endosperm of certain Caryophyllee,
Chenopodiacere, Graminer, &c. The numerous new observations which
his paper contains have remained comparatively unknown in consequence
of the extraordinary theories which he builds upon them, and of remarkable
errors in matters of fact.
296 A. F. W. SCHIMPER.
nothing can be seen of them, or of the corpuscles which have
produced them.
The starch-forming-corpuscles of many plants have the
Same properties and are formed in the same way as those
which have been described above, but they differ from them,
more or less, in the mode in which they produce the starch-
grains. In many instances the starch-grains are produced
in the manner described above, but the number of them is
smaller, and they attain a more considerable size. This is
the case in the rhizome of Amomum cardamomum, which
supplies excellent material for investigation.
The starch-grains in the rhizome of 4A. cardamomum}
(figs. 16—20) are large and club-shaped when mature, and
they exhibit distinct internal differentiation. The hilum is
very excentric, and lies towards the thicker rounded end;
the other end is truncate. Compound grains, consisting of
two or three smaller ones, are not uncommon.
The starch-forming-corpuscles resemble those in the epi-
dermis of Philodendron in respect of size, form, and mode of
development, but they are paler and less stable. The starch-
grains are formed in them just under the surface, or even on
it, and are either solitary or two or three together. They
are at first hemispherical, attached by the flat surface to the
starch-forming corpuscles, which are flattened at the points
of contact ; they subsequently assume a club shape. The
hilum always lies towards the free end of the grain. When
two or three starch-grains are formed, compound grains are
produced. The starch-forming-corpuscles become at first
larger, and at the same time less dense; at a later stage,
when the starch-grains have nearly attained their definitive
size, the corpuscles can no longer be distinguished, or deli-
cate gelatinous remains of them can be made out by the use
of iodine solution. When the grains are mature it is im-
possible to detect any trace of the corpuscles.
The starch-forming-corpuscles in the rhizome of Colocasia
antiquorum differ from those which have just been described
only in that they give rise to starch-grains throughout their
whole mass. The very numerous grains formed in a cor-
puscle cohere to form spuriously compound grains. This
mode of the development of starch-grains is more fully de-
scribed in the following example, in which I have studied it
more closely.
The starch-grains in the endosperm of Beta trigyna
(figs. 30—32) are large, spherical, or somewhat elongated,
1 T obtained this from the Botanic Garden at Strassburg. As the plant
was not in flower at the time I cannot vouch for its identity.
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS. 297
and they consist of innumerable minute polyhedral grains.
In ripe seeds these minute grains have always become
separate.
Immediately before the first formation of the starch-grains
the starch-forming-corpuscles are spheres of rather larger size
and lower refrangibility than those in the epidermis of PAzlo-
dendron grandifolium. They are very numerous, and they are
especially collected on the lateral walls of the cells. The
mode of their development differs but little from that which
has already been described in other cases. In the youngest
cells the nucleus, which is usually suspended in the cavity
of the cell, is surrounded by a very thick layer of peculiarly
glistening protoplasm. This becomes paler, and a number
of bright points become apparent in it; these enlarge into
spheres, and the remainder assumes the appearances of ordi-
nary finely granular protoplasm. Some spheres also make
their appearance in the strands of protoplasm which connect
the protoplasm around themselves with the parietal layer,
and some appear also in this layer itself. The corpuscles
enlarge, their refrangibility diminishing at the same time,
and the protoplasm with the nucleus coalesce with the
parietal layer.
The first starch-grains are apparently formed in the peri-
pheral portion, but this has not yet been quite definitely
ascertained. ‘The corpuscle soon becomes turbid in con-
sequence of the presence of a number of minute granules
which increase in size and become starch-grains. The
whole body increases considerably in size, and it may either
retain its spherical form or become more or less elongated.
The substance of the corpuscle diminishes, and finally
disappears altogether, whilst the starch-grains fill up the
whole space, and become polyhedral in consequence of
mutual pressure. In this way the above-mentioned com-
pound grains are produced, which must therefore be regarded
as spuriously compound.
The starch-grains in the endosperm of Melandryum
macrocarpum (figs. 24—29) are large, spherical, or ovoid,
and consist of innumerable minute grains, which, as in
Beta, separate as the seed ripens.
The starch-forming-corpuscles which produce them are
moderately large, spherical, or spindle-shaped, and lie in the
parietal protoplasm upon the nucleus. They are few in
number. They differ from those which have been already
described in that they are formed at various points in the
protoplasm, which is, from the first, parietal. The process
isin other respects essentially the same in all cases, The
VOL, XXI,——NEW SER. U
298 A, F. W. SCHIMPER,
thin protoplasmic lining of the youngest cells is very dense
and glistening ; its surface is at first smooth, but it becomes
uneven. The prominences become rounded off and form
spheres or spindles, whilst the substance between them
becomes ordinary protoplasm.
The formation of starch-grains begins very early, even
before the complete differentiation of the starch-forming-
corpuscles. It is indicated, as in Beta, by a turbidity in
the corpuscle,and by its turning blue when treated with
iodine. The grains become gradually larger and more
numerous, and polyhedral in consequence of mutual pres-
sure. The substance of the corpuscle diminishes and dis-
appears.
' The young white tubers, surrounded by leaves, and the
roots of Phajus grandifolius, contain rather large starch-
grains of a triangular, much flattened form, and of definite
excentric structure (figs. 33—41).
The young starch-grains are attached by their posterior
ends to rod-shaped bodies which lie parallel to the broadest
sides of the starch-grains. These rods give the same re-
actions as the starch-forming-corpuscles, and the study of
their development shows that they are bodies of this kind.
When treated with water they become spherical vesicles and
then disappear.
Bodies of this kind, which are not attached to starch-
grains in older cells, are found in the epidermis, both of old
tubers which have become green and in young ones, col-
lected around the remarkably granular nucleus.’ In very
young cells they produce small starch-grains. I was able
to study the development of these peculiar starch-forming-
corpuscles, but the small amount of the material prevented
me from making out all the details with certainty. In the
youngest cells the nucleus is surrounded with a layer of
dense glistening protoplasm, as in the epidermis of Philo-
dendron. At a later stage numerous minute delicate spin-
dles are found lying in the protoplasm which now presents
its ordinary appearance. These spindles soon give rise
to small starch-grains which disappear. The corpuscles
enlarge and assume, even when the starch is being formed, a
rod-shape.
Exactly the same apparently takes place in the root (figs.
33—36), where it is easy to observe the starch-forming-cor-
puscles before the appearance of the starch-grains and to
follow the development of the latter. The corpuscles which
are collected round the nucleus, and which are at first
1 Gris, ‘Ann. d. Sci. Nat.,’ sér. 4, t, vii, pl. 8, fig. 4.
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS. 299
spindle shaped, form on their surface one starch-grain, or
sometimes two or three, which is at first conical; when it
has attained the thickness of the corpuscle, which has in the
meantime become rod-shaped, it increases in size almost
solely in a plane which is parallel to that of the corpuscle.
It appears from this that not only does the unequal growth,
which produces the excentric structure, depend upon the
mode of nutrition of the grain, but also the unequal in-
crease of its diameters which produces the flattened form.
The layer of the corpuscle which immediately invests the
grain is delicate, and is more or less swollen (fig. 41). The
further behaviour of the corpuscles is similar to that de-
scribed in other cases; they become less dense and stable,
are reduced to a small swollen gelatinous residue, and
finally disappear.
The formation of starch in the parenchyma of the young
tubers (figs. 37—40) takes place in essentially the same way
asin the root. I have not succeeded in observing the cor-
puscles in this case before the appearance of the starch-
grains: the apices of the minute spindles already contained
them. Both corpuscles and grains increase in size and
become much larger than in the root.!. Their further beha-
viour will be described in the following section:
The starch-grains in the rhizome of Canna gigantea (figs.
46—49) are very large, triangular, and flattened; they are
excentric, and are either simple or partially or entirely com-
pound, consisting of a few, seldom more than ten, small
grains which are usually arranged in a row.
The starch-forming-corpuscles resemble those of Amo-
mum Cardamomum in their development, and at first in
their form also; they differ from them only in that they
usually contain a tabular crystalloid, which is either octa-
hedral or cubical, and which only becomes apparent on treat-
ment with water. The first stages in the development of the
starch-grains are the same as in Amomum; they are formed
excentrically or even superficially in the corpuscle, and there
may be one, two, or three; they have at first a rounded form
which is somewhat flattened at the point of attachment.
The corpuscles now behave very differently from those
of Amomum ; they grow in one direction only and acquire
an elongated form. ‘The starch-grain grows, as in Phajus,
in a plane which is parallel to that of the corpuscle which
formed it, and the hilum lies towards the free end. The
crystalloid lies in a projecting portion of the corpuscle.
The further behaviour of the corpuscles is the same as it
! This is weil seen in sections which have been hardened in alcohol,
300 A, F. W, SCHIMPER.
is in the preceding case. They become gradually less dense
and resistant, and form only a delicate investment to the
posterior ends of the starch-grains by the time that they
have obtained one-half of their definite size.
In certain cells of the cortex! spindle-shaped bodies contain-
ing crystalloids are found, which are doubtless starch-forming-
corpuscles which have produced no starch (fig. 54). In
the external part of the cortex the corpuscles and the starch-
grains are small, and always present the same appearance as
the apical region in its earlier stages.
An account has now been given of all the. various modes
of the formation of starch which I have as yet observed.
They may be conveniently tabulated as follows :
1. Starch-forming-corpuscles spherical.
a. They are formed only in the protoplasm which
invests the nucleus:
(a) They form starch throughout their whole
mass ; Colocasia.
(8) They form starch only in their periphery ;
Philodendron, Amomum.
b. They are formed in the protoplasm surrounding
the nucleus, but to some extent also in other
parts:
(a) They form starch throughout their whole
mass ; Beta trigyna.
c. They are formed in all parts of the protoplasm :
(a) They form starch throughout their whole
mass; Melandryum.
2, Starch-forming-corpuscles, spindle-shaped.
a. They are formed only in the protoplasm which
invests the nucleus :
(8) They form starch only in their periphery ;
Phajus.
c. They are formed in all parts of the protoplasm :
(a) They form starch throughout their whole
mass ; Melandryum.
3. Starch-forming-corpuscles at first spherical, subse-
quently elongated.
a. They are formed only in the protoplasm which
invests the nucleus :
(8) They form starch only in their periphery ;
Canna gigantea.
1 This observation was made on Canna discolor, which in other respects
resemble the species referred to above.
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS. 301
Other starch-grains which I have studied cannot he
arranged under one or other of these types, inasmuch as I
have not been able to make out all the details of their develop-
ment. In many cases the development of the starch-forming-
corpuscles was not observed, though it could be inferred
from their position in the cell. In other cases it was
impossible to see the first appearance of the starch-grains.
The following conform to the type of Amomum Carda-
momum, namely, other Scitaminee such as Thalia setosa,
Elettaria Cardamomum, Costus Malortieanus ; the Potato, so
far as observations made on the cortical part of young
potatoes go (the more central portions were too opaque in
consequence of the presence of the starch grains); the
rhizome of Iris florentina, in which the starch-forming-cor-
puscles have a peculiar granular appearance ; the parenchyma
of the pith of Philodendron grandifolium. In the following
cases the same relation between starch-grain and starch-
forming-corpuscles was observed, although I was unable to
ascertain the mode of development of the latter; in the
bulbils of Ficaria ranunculoides ; in the cortical parenchyma
of the rhizome of various species of Peperomia; in the
cortical parenchyma of the scales of a Tydea; in the tubers
of Dioscorea alata ; in the root of Gunnera scabra.
Silene inflata and Lychnis dioica belong to the Melandryum
type.
The observations made on Phajus probably hold good
with reference to the other allied Orchidaceous plants—
Acanthephippium,! for instance.
The other species of Canna resemble Canna gigantea, and
perhaps Curcuma zedoaria does also; the minuteness and
indistinctness of the corpuscles in this plant made it im-
possible to observe them accurately ; in their first formation
and in their mode of development they resemble those of
Amomum, and at a later period they appear to become
elongated like those of Canna.
3. When we compare the starch-forming-corpuscles with
other bodies contained in cells their resemblance to chloro-
phyll-corpuscles at once suggests itself. In their composition
they appear to be essentially the same as the leucophyll-
corpuscles? which are found in the more internal cells of
etiolated stems, and which are quite colourless and very un-
stable. Further, there is a singular similarity in the mode
of development; the mode of formation of the starch-
1 Gris, loc. cit., p. 196. 3
? I prefer this term (which was suggested by Sachs) to the term “ etiolin-
corpuscles,” for these corpuscles appear frequently to contain no etiolin.
302 A, F. W. SCHIMPER.
forming-corpuscles in the endosperm of Melandryum agrees
in all important points with the mode of development of the
chlorophyll-corpuscles of many leaves, and their development
in the epidermis of Philodendron has its perfect analogue in
the formation of chlorophyll-corpuscles in many stems
(e.g. of Cereus speciosissimus!), and in the leaf of Vanilla
planifolia.2. Again, the starch-forming-corpuscles, like the
chlorophyll-corpuscles, produce starch-grains, although the
origin of the grains is different in the two cases, inasmuch
as in the latter they are the products of assimilation, whereas
in the former they are formed from organic substances which
had been assimilated elsewhere.
A distinct analogy appears in the relation in space of the
starch-grains to the point of their formation ; the same two
types which we found in the chlorophyll-corpuscles recur in
the starch-forming-corpuscles ; and, further, as has already
been pointed out, the behaviour of the starch-forming-cor-
puscles, after the formation of the starch-grains, is quite
similar to that of the chlorephyll-corpuscles.
But these relations may be extended much further. In
most cases the starch-forming-corpuscles may be actually
converted into chlorophyll-corpuscles under the influence of
light.
This conversion may take place normally and regularly in
the development of a plant-organ; this is the case when the
younger parts of the organ are protected from the light,
either by a thick covering of leaves or by the soil, and are
exposed to its influence at a later period (leaves of Iris,
tubers of Phajus grandifolius).
In organs which remain, as a rule, permanently in the
dark, the conversion of starch-forming-corpuscles into
chlorophyll-corpuscles takes place as soon as they are
exposed to light; in this way the false chlorophyll-cor-
puscles are produced which have been known, in the potato
for instance, for so long.
Certain parts of some organs are exposed to light, whereas
others are more or less protected from it; this is the case,
for instance, in stems, the bases of which are buried in the
soil (e.g. Peperomia, Begonia, &c.), and in thick opaque
organs of which only the external cells are affected by light
(e.g. Philodendron grandifolium). In such cases all pos-
sible intermediate stages between starch-forming-corpuscles
and chlorophyll-corpuscles can be found.
This conversion always takes place in the same way ; the
? From my own observation.
2 Gris, loc. cit., p. 188.
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS, 803
starch-forming-corpuscles increase considerably in size, the
contained starch-grains undergo partial or complete absorp-
tion, and at the same time a formation of pigment takes
place.
I will content myself with briefly describing a few
instances.
The conversion in question which accompanies the
normal development of an organ appears to be of very
general occurrence. The young leaves of Iris florentina
contain no chlorophyll, but the parenchymatous cells which
abut upon the fibrovascular bundles contain starch-grains
which are attached to large starch-forming-corpuscles ; these
portions of the leaves subsequently become green in conse-
quence of the conversion of the starch-forming-corpuscles
into chlorophyll-corpuscles.
The behaviour of the starch-forming corpuscles in the
tubers of Phajus grandifolius (figs. 42, 43) is very remark-
able. The tuber is at first surrounded by a dense invest-
ment of leaves, but, in consequenee of its growth, it gradu-
ally emerges and the leaves die off. The tuber is at first
quite white, but it soon turns bright green after exposure to
light. Close observation shows that the starch-forming-
corpuscles increase considerably in size, that the contained
starch-grains are partially absorbed, and that they develope
into rod-shaped chlorophyll-corpuscles ; bodies of this kind
can be found especially well-developed in the bundle-
‘sheaths of the upper parts of the tuber. Even when the
starch-forming-corpuscle has been reduced to a small
gelatinous residue, it becomes green in the manner de-
scribed. In the external cells of the cortex only a partial
conversion of the starch-forming-corpuscles takes place, and
it is confined to that part of the corpuscle to which the
starch-grain (which is in this case always very small) is
attached ; it becomes a somewhat elongated chlorophy]ll-
corpuscle, the starch-grain undergoing partial or complete
absorption, which remains attached to the portion which has
remained unaltered. In this way very curious bodies are
formed, which Gris! has already observed in Phajus and
Acanthephippium.
In subterranean organs which are exposed to light the
effect is the same. The outer cortical cells of the potato are
especially instructive. The cells which lie immediately
1 Gris, loc. cit., p. 195. I have never been able to observe the spherical
bodies which he describes, in uninjured cells; but they always appear under
the action of water.
804: A, F. W. SCHIMPER.
beneath the cork, contain, according to Wiesner,! etiolin-
corpuscles which become chlorophy!l-corpuscles under the
influence of light. These bodies, which are really starch-
forming-corpuscles, and which, as in all other cases, pro-
duce no starch in the cortical cells, become converted, as far
as I could observe, into very small and only slightly
coloured chlorophyll-corpuscles, whereas those which are
situated in the more internal cells and which contain starch-
grains become converted into large and brightly coloured
chlorophyll-corpuscles. When the contained starch-grains
are very small they undergo complete absorption. In the
still more internal parts of the tuber, where the starch-grains
are very large, the starch-forming-corpuscles are reduced to
a small gelatinous residue, they can naturally only become
delicate ill-defined chlorophyll-corpuscles.
These facts can be very readily made out in the rhizome
of Canna (figs. 5|0—53) ; here, in correlation with the form
of the starch-forming-corpuscles, the chlorophyll-corpuscles
are sickle- or spindle-shaped (spherical in the outer cells)
and contain crystalloids.
The investigation of the following gave the same results ;
the rhizome of Iris florentina, of Costus Malortieanus, the
scales of a Trevirania, the roots of Gunnera scabra, and of
Phaus grandifolius, which resemble the tubers (fig. 45).
Not all starch-forming-corpuscles, however, are capable of
being converted into chlorophyll-corpuscles, even when
their whole development goes on in the presence of light
(epidermis of Philodendron and Phajus, endosperm of
Caryophyllee).
It is evident, from what has been stated above, that there
is a complete resemblance between starch-forming-corpus-
cles and leucophyll-corpuscles, and even with chlorophyll-
corpuscles in their first stages of development; the question
naturally suggests itself as to whether or not these cor-
puscles are identical. The only obvious difference between
them is the former can produce starch-grains from assimilated
substances, whereas the latter cannot produce any starch
at all, so far as is at present known.
A more careful investigation shows, however, that even
this difference is by no means constant; and that, on the
contrary, these corpuscles completely resemble each other in
this respect also.
It is well known that the mesophyll of etiolated plants,
which have not yet exhausted their reserve materials, con-
tains no starch, although it is present in quantity in their
1 Wiesner, ‘ Uester. Bot. Zeitschr.,’ 1877.
RESEARCHES ON THE DEVELOPMENT OF STARCH-GRAINS, 805
stems and petioles, and in the bundle-sheaths of their leaves.
This starch, which is obviously not a product of assimilation,
is produced by the leucophyll-corpuscles. Examples of this
can be found in the Hyacinth (bundle-sheath), in the stem of
Begonia cucullata (figs. 55, 56), and of Ozalis Ortgiesiz, in
the cortex of the stem of Philodendron grandifolium.
These leucophyll-corpuscles are very faintly tinged with
yellow, if at all. They gave rise, to the cases observed, to
starch-grains in their periphery, just like the chlorophyll-
corpuscles which would have been produced there under or-
dinary circumstances. In those cases in which the starch-
grains have a definite structure, as in the stem of Begonia
cucullata, they are excentric, and the more developed side
is the one which is in contact with the leucophyll-corpuscle ;
this naturally removes any doubt as to the physiological
significance of the corpuscles.
The question now arises as to whether or not the property
of forming starch out of assimilated materials is peculiar to
the leucophyll-corpuscles and to the starch-forming-cor-
puscles, and is not possessed by the chlorophyll-corpuscles ;
and, further, whether this property is lost when these cor-
puscles become converted into chlorophyll-corpuscles.
In order to obtain an answer to this question a root-stock
of Tradescantia rubella was kept in the dark until the large
starch-grains which were present in the mesophyll had
entirely disappeared ;' it was then exposed for some time to
light, which was sufficiently intense to effect the formation
of normal chlorophyll-corpuscles, but not sufficiently intense
to cause any formation of starch in consequence of assimila-
tion.” The investigation of the axillary branches which
were produced from it under these conditions (the apices of
the branches were carefully removed before the commence-
ment of the experiment) showed that there was no starch in
the mesophyll, but that it was present in considerable
quantity in the chlorophyll-corpuscles of the bundle-sheaths
of the leaves and of the parenchyma of the stem.
These observations are not, as might appear at first sight,
by any means adverse to Sach’s theory, that the starch-grains
found in chlorophyll-corpuscles are products of assimilation.
On the contrary, they confirm this theory in certain points.
The fact that the formation of starch in the mesophyll de-
pends upon the same conditions as assimilation, whereas it
' Sach’s method (‘ Exp. Phys.,’ p. 322) for the detection of very small
quantities of starch was made use of.
* That no assimilation took place was shown by the fact that the chlo-
rophyll-corpuscles of the mesophyll produced no starch.
306 A. F. W. SCHIMPER.
is independent of light in other parts of plants so long as
there are reserve materials to draw upon, can only be ex-
plained by the assumption that starch can be formed in the
chlorophyll-corpuscles of the mesophyll only by assimilation,
and that in the other cases it has a different origin. The
chlorophyll-corpuscles of the parenchyma of the stem and
of the bundle-sheaths of the leaves can form starch, both by
assimilation and by the conversion of assimilated substances
conveyed to them from other parts. In other words, these
chlorophyll-corpuscles combine the functions which are
peculiar to chlorophyll-corpuscles with those which are per-
formed by starch-forming-corpuscles. This assumption is
further justified by the fact that the mesophyll is the prin-
cipal seat of the assimilatory function, whilst the bundle-
sheaths of leaves and the parenchyma of petioles and of
stems are conducting tissues for starch; the parenchyma of
stems is also to some extent a reservoir in which it is
deposited.t
It is evident that the starch, which makes its appearance
as the first visible product of assimilation, is not directly
formed from carbon and water, but that a number of inter-
mediate products must be formed.”
We may assume that the substances which are conveyed
to the chlorophyll-corpuscles in question are nearly allied to,
or even identical with, these intermediate products; hence
the conversion into starch of the substances which have been
formed in the chlorophyll-corpuscle itself, and of those which
have been conveyed to it from other parts is really one and
the same process.
The results of this investigation tend to show that there
is no such great difference between assimilating and non-
assimilating cells, as was thought to exist. In a cell which
contains no chlorophyll there are certain organs which pro-
duce starch, and these organs are nothing more than im-
perfectly developed chlorophyll-corpuscles, which may
develope into perfect chlorophyll-corpuscles under the in-
fluence of light. On the other hand, chlorophyll-corpuscles
are not always merely assimilatory organs ; they perform in
the conducting tissues and in the reservoirs of material the
same functions as the starch-forming-corpuscles in cells
which do not assimilate; that is, they produce starch from
assimilated substances which are conveyed to them from
other parts of the plant.
1 Sachs, ‘ Exp. Phys.,’ p. 380 395 e¢ passim.
2 Sachs, ‘Exp. Phys.’ Pringsheim has recently discovered such an in-
termediate product, and has termed it hypochlorin (‘Monatsbericht d.
preuss. Akademie in Berlin,’ 1879).
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE, 807
Upon the Cause of the Striation of VoLuntary Muscunar
Tissuz. By Joun Berry Haycorart, M.B., B.Sc., F.R.S.E.,
Senior Physiological Demonstrator in the University of
Edinburgh. [Communicated to the Royal Society, of London,
December Ist, 1880.]
Tue structure of striated muscular tissue has occupied the
attention of many histologists, and various, often antagonistic,
have been the views held from time to time since Schwann first
investigated this difficult subject.
I bring forward with much caution and hesitation any
opinions of my own, nor should I venture thus far, did I
not consider my views susceptible of direct proof, or disproof,
not being matters of mere speculation, which may or may not
be true, and which would tend, by their introduction to the
literature of the subject, to make confusion worse confounded.
In this paper an attempt will be made to account for many of
the observed structural phenomena of muscle on simple laws of
geometrical optics, which will, if it be successful, reduce the
subject to comparative simplicity. I shall commence by giving
a sketch of the views of those physiologists who have especially
written upon the structure of muscle. This must not be looked
upon as a complete history, for I shall leave out entirely points
which do not concern us here.
A short historical sketch of the views held upon the structure
of striated muscle.—The writings of Mr. Bowman form the most
important and brilliant contributions to the literature of this
subject, and taking him as a landmark, it is convenient to speak
of investigators before or after his time. Among the former
Schwann, quoted; by Miiller (‘ Physiology,’ translation by
Baly, vol. ii, p. 878), describes the striated voluntary fibre, in-
dicating its shape and size. The cross markings were observed
by him, and, indeed, with one or two remarkable exceptions, by
all the early observers (Lauth and Wagner, in Miiller’s ‘ Archiv
fir Anatomie und Physiologie, und Wissenschaftliche Medicin,’
pp. 4 and 318 of the year 1835). Schwann, with Bauer,
Krause, Miiller, Home, Valentin, and Milne Edwards recognised
the important fact that each fibre is composed of a number of
threads or fibrillz, packed side by side and joined together by a
transparent tenacious fluid (Krause), and, moreover, that these
threads or fibrille are cross striated, as is the fibre itself.
Although Schultze describes the fibrille as being uniform fila-
ments, he is alone in this opinion, most of his contemporaries
808 JOHN BERRY HAYCRAFT.
recognising the beaded appearance.1_ The beaded thread was the
cause of some dispute, for the question arose, Was it a linear
series of globules or a moniliform filament? and the final settle-
ment of this must, indeed, have been a matter of great difficulty
to those older savants, when we consider the imperfect lenses at
their disposal. Krause and others maintained the former view,
while Schwann held that which subsequent investigators have
shown to be the correct one. The fibrille, according to Schwann,
present a very regular succession of bead-like enlargements,
darker than the very short constrictions which lie between.
Thus, before the time of Bowman, the following important facts
had been made out, namely, that the fibre is composed of a
bundle of beaded fibrillee cemented together, and that the fibrille
are cross striped, giving the whole fibre a like appearance of
striation. Erroneous views had often, it is true, been advanced,
but these had never received general acknowledgment. Mr.
Skey (‘ Phil. Trans.’ of 1837), for instance, considered the fibres
to be tubes filled with a soluble gluten, the strie surrounding
and binding them together. Leeuwenhoek had a somewhat
similar view of the construction of the cross strie, and Proch-
aska considered them as depressions caused by the clasping of
neighbouring capillaries and thready tissues.
Mr. Bowman communicated to the Royal Society, in 1840, a
paper “On the Structure and Movements of Voluntary Muscle,”
in which he confirmed many of the opinions of his predeces-
sors, adding, at the same time, much of what was fresh to our
store of knowledge. He it was who first described the thin
elastic membrane (sarcolemma) covering and ensheathing the
fibres, showing how easily to demonstrate its existence, and giving
figures of it, which have been copied into most modern histo-
logical works. The nuclei of the sarcolemma he also figured,
but what most concerns us is his description of the cross stria-
tion. Mr. Bowman, I believe, first pointed out that not only can a
fibre be split up longitudinally into fibrille along certain dark
lines which may generally be seen, even in fresh preparations,
but that it splits up transversely along the dark stripes. Hach
fibrilla may, therefore, be split up into tiny segments across the
dark strie. ‘‘On the whole, little doubt remains in my mind
that the fibrillaee consist of a succession of solid segments or
beads connected by intervals generally narrower, and I believe
the beads to be light, and the intervals the dark spaces when the
fibrilla is in exact focus.” His idea of a fibre naturally follows
from that just given of a fibrilla, and, quoting again from him,
1 Consult a drawing by Allen Thomson in illustration of Dr. Martin
Barry’s paper on the “Structure of Muscular Fibrils,” ‘ Phil. Mag..,’ ser.
4, vol. 6, plate v, fig. 2.
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 309
we find “a fibre consists of sarcous elements (so he termed the
little segments or beads) arranged and united together endways
and sideways, so as to constitute in these directions respectively
fibrillee and discs, either of which may in certain cases be
detached as such,” and “‘ the dark longitudinal striz are shadows
between fibrille, the dark transverse strie shadows between
discs.”
It will be seen that in one particular Bowman disagreed with
Schwann and the older writers, and at the same time with those
of more recent date. According to him, the bead was light and
the constriction dark, when the muscle was in exact focus, a
description at variance with everyone. In the same paper he
mentions this remarkable fact, that on altering the focus the
stripes were reversed ; he must have examined it—this bears in
a most important way on our investigations, to be afterwards
described—in the reverse focus of what it is ordinarily figured
in. His view of the form, and the splitting of the fibre, was
probably correct, for he described the cleavage as occurring in
the narrow part, which appeared to him, focussing as he did, to
be dark, and indeed it is often difficult to say which it is,
whether dark or light, for, as we shall more particularly mention
afterwards, the slightest alteration of the focus is sufficient to
reverse the appearance of the fibre. Bowman, moreover, ac-
counted for these light and dark parts of the fibrille, comparing
a muscular filament to a glass rod with alternate swellings and
depressions, which, when viewed with transmitted light, gives
just the same appearance, and from a study of his paper, although
it is here somewhat indefinite, I judge that he concluded the
moniliform shape to be a cause of the striping.!
Now, this last-named and important discovery of Bowman’s
has, I believe, completely been lost sight of, for no mention of
it can be found in any modern monograph nor in any systematic
text-book that I have examined. ‘The striking points in the
paper and in the figures he gives, is the splitting up of the fibre
into transverse discs and the demonstration of the sarcous
elements as before quoted. This, together with the sarcolemma,
every one connects with the name of Bowman. Modern inves-
tigators have worked mostly at the cross striping of muscle,
and have found it more complicated than Bowman described,
owing, no doubt, to the use of better glasses; while he ex-
plained the phenomenon as due simply to the shape of the
fibres—believing, however, probably that it was due also to
1 Bowman, nevertheless, seems to consider the dark stripe of a different
structure from the light, not so much from the shading, but from the
transverse cleavage. He is not quite definite here, but this is the impres-
sion I have gained from a careful perusal of his paper.
310 JOHN BERRY HAYCRAFT.
structural differences—modern investigators have introduced
hypotheses to account for it, which entirely imply differences of
structure along the filament. The reason of this is, if I may
express an opinion, that his theory has been completely lost
sight of, and that it was followed by the discovery of startling
facts, which at first sight seemed to set it on one side.
In discussing the views of modern inquirers, I shall not, in
all cases, consider them in the order of their priority, and illusion
will not be made to much that has been written upon this
subject, which, indeed, may safely be put on one side.
The light stripe—dark stripe of Bowman—has been shown by
Dobie, Busk, and Huxley, to be traversed by a very fine dark
band, or rather line “ Querlinie” dividing it into two equal parts.
We shall speak of this as Dobie’s line, or the dark stripe in the
centre of the light. (Fig.1, p, woodcut.) Then, again, the
dark stripe is traversed in its centre by a lighter band called
Hensen’s stripe.’ (Fig. 1, #, woodcut.) Other bands border
this stripe, but as they are certainly not to be seen in all speci-
mens, however well prepared, and as we shall presently account
for them, they need not trouble us here.
As early as the year 1839, Boeck showed that muscle refracts
light doubly, which statement was, however, modified in 1857
by Briicke. The latter examined muscles prepared in alcohol
by polarised light, and found that the dark stripe (dark in
ordinarily non-polarised light) appeared luminous in the dark
field of the microscope, and that the light stripes were dark
when the Nicols were crossed. The dark stripes, therefore,
appeared to be doubly refracting (anisotropous), and the light
stripe singly refracting (isotropous), the fibre consisting of
singly and doubly refracting discs alternating one with another.
These observations he verified by an examination of the fibre
with thin plates of selenite and mica. The views of Briicke
have, in their turn, received considerable modifications which
will be understood by reference to a diagram. Fig. 2 expresses
very well the results of my own observations, which are in accord-
ance, | find, with those of other observers. (See the ‘Handbuch
der Physiologie,’ by Dr. L. Hermann, 1879, p. 20.) The black
part of the diagram corresponds with the portion of the muscle
which singly refracts light (isotropous), while the light shaded
parts correspond with the anisotropous substance.
This diagram does not, it will at once be seen, correspond
with the views held by Briicke, for the great mass of the light
stripe, with Dobie’s line in the centre of it is anisotropous, the
1 This stripe was also described by Dobie in the ‘Annals of Natural
History for 1849,’ and it may be called Dobie’s light stripe. as
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE, 311
dark band, as with Briicke, being anisotropous. The most
recent view is, then, that both the light and the dark stripes
doubly refract light, but that there are bands which lie between
them and which are singly refracting. With the appearance
Fic. 1.—This represents diagramatically a fibre viewed with a very high
power. The borders are wavy, and the cross stripes correspond with
these irregularities. (D) marks the position of Dobie’s lines placed in
the centres of the depressions seen at the border. (H) represents
Hensen’s stripes or Dobie’s light stripes placed on the summits of the
ridges in the centres of the dark bands.
Fic. 2.—This shows the appearance of the fibre with crossed nicols. The
shaded parts are seen on the slopes between the ridges and depressions.
They are explained fully in the text.
Fic. 3.—A fibre is represented as seen with three positions of the lens.
In (A) the lens is elevated, and the depressions appear dark. In (c)
the lens is fully depressed, when the stripes are reversed, the depres-
sion being now light with Dobie’s line in the centre, and the crests
dark with Dobie’s light stripe in the midst. In (B) the intermediate
stage is seen.
which would partially warrant such a conclusion, I can entirely
agree, but I shall endeavour to show hereafter how this may
most satisfactorily be explained. It will readily be seen how
Briicke’s view, until quite recently accepted, would drive one
to the conclusion that the light and dark stripes represent two
different structures alternating in the length of the fibre, and
this is corroborated by statements as to the action of staining
agents on the tissues.
Picric acid stains muscle very readily, but it is but faintly
tinted by carmine, logwood, or eosine, although Ranvier, in his
‘Traité Technique d’Histologie,’ states that he has obtained
312 JOHN BERRY HAYCRAFT.
very beautifully stained preparations of insects’ muscle, when
using Boehmer’s solution of logwood. According to this observer,
the dark stripes as well as Dobie’s lines are stained, while the
rest of the fibre remains colourless. Klein, in his ‘ Atlas of
Histology,’ figures the sarcous matter of the dark band clearly
tinted, while that of the light stripe is absolutely colourless.
The statement will not be far wrong, that every one at the pre-
sent time considers the dark and light stripes as representing
two different structures, distinct one from another in their phy-
sical properties, for the dark stripe is spoken of as possessing a
higher refracting power than the light, and chemically, for their
compositions have already been hinted at by more than one ob-
server. The dark stripes are looked upon by most as the true
contracting part of the fibre, and they are termed the sarcous
discs, or ‘ Muskelprismen,” “ Hauptsubstanz,” or masses of dis-
diaclasts, and the light stripes as merely connecting matter (Zwis-
chensubstanz), or “ Muskelkistchenfliissigkeit.”? Dobie’s line—
more especially from the dipping down and attachment of the
sarcolemma in insects’ muscle at this point—has been looked
upon (Krause, ‘ Allgemeine und Microscopische Anatomie,’ sec-
tion “ Muskel System,” pp. 80—90) as a delicate transverse mem-
brane. ‘This view has received the assent of such microscopists
as Klein and Ranvier, but not of Wagener (‘ Jahresberichte der
Anatomie und Physiologie, Hofmann and Schwalbe) and
Rutherford (‘Text-book of Physiology,’ p. 128), who describe
Dobie’s line as consisting of a row of dots. Engelmann, indeed,
describes a row of dots on either side of this line.
Krause would have us believe that the fibre is divided by these
membranes into a linear series of little boxes, each box or casket
“Miiskelkistchen’’ containing a dark stripe with (as the membrane
lies in the centre of the light stripe) one half of that on either
side. Merkel (‘ Lehrbuch der Gewebelehre,’ Stuttgart, 1877,
p- 83), to make the Miskelkastchen self-containing, affirms that
the membrane of Krause is double. As to the stripe of Hensen,
this is by very many looked upon as still another structure lying
in the centre of the dark stripe ; it is in many fibres very clearly
to be made out, its border being well defined, and in stained
preparations (logwood) it has decidedly a lighter tint than the
rest of the stripe. Still, some (Krause) look upon it as an in-
dication of the highly refracting power of the dark stripe, com-
paring the appearance with the light centre of an oil globule.
The other cross strie, of which there are many described by
some observers, but none at all universally accepted, are, as a
rule, considered as indicating further complications in the muscle
fibre ; indeed, the Miskelkistchen, by most advanced micro-
scopists, although not +1, of an inch in length, consists of
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 313
some ten or twelve different parts. We may postpone, I think,
indefinitely the consideration of these details.
While there is great unity as to the appearance of a fibre
during a state of rest, the changes which the fibre undergoes
when passing into the contracted condition are not at all under-
stood. Not only does one fail to find among histologists agree-
ment as to the changes in appearance, but the interpretations of
these are as numerous as the investigators themselves. All are
agreed that, during contraction, the fibre asa whole shortens and
thickens, but the changes in form which the cross strize undergo
are not understood so well.
Klein, in his ‘ Atlas of Histology,’ maintains the broadening
of both stripes transversely, the dark stripe becoming thinner in
the long axis, and the bright stripe more opaque. Ranvier
(‘Traité Technique d’Histologie,’ p. 459) states that the only
points one can conscientiously observe in the contraction of a
living fibre are, that a knot or bulging forms, in which the dark
bands approximate, being only separated by Dobie’s line. This
led him to believe that the dark bands are the true contracting
part of the fibre. Ranvier worked especially with osmic acid,
fixing the fibres when at rest and during contraction. W.
Krause (‘ Allgemeine und Mikroscopische Anatomie,’ p. 92)
describes the contraction as follows:—The thickness (in the
length of the fibre) of the dark stripe or an isotropous substance
remains the same as far as can be seen, while the thickness of
the isotropous substance “ Zwischensubstanz’’ becomes less.
From this he argues that the substance of the clear stripe, which
he considers as fluid “ Muskelkistchenfliissigkeit,” passes between
the little elements of the dark stripe, causing their lateral sepa-
ration, and therefore broadening and shortening the fibre. Hn-
gelmann (“Neue Untersuchungen iiber die Microskopischen
Vorgiinge bei der Muskelcontraction,” in ‘ Pfluger’s Archiv,’
Band xviii) is certain that the light stripe durig complete
contraction becomes darker than the dark stripe, and that there
is a period, as naturally follows from this observation, when
the fibre is quite unstriated. The stripes are, in fact, reversed,
the bright one becoming the darker, and vice versd. Both
stripes narrow, but especially the bright one. Engelmann ad-
vances a theory to account for this, holding that the cause of
contraction is the passage of fluid from the isotropous clear -
stripe into the anisotropous substance; the former shrinks and
the latter swells. Most startling is the view of Merkel (‘ Hof-
mann und Schwalbe,’ vol. i, p. 116), who believes that the dark
stripe shifts its position, arranging itself by Dobie’s line, while
the light stripe passes to the centre.
It is, as will readily be admitted, somewhat difficult to know
VOL, XXI,—NEW SER. x
314. JOHN BERRY HAYCRAPFT.
what to believe, for there is such entire disagreement among
physiologists as to simple facts, to say nothing of any conclusions
which may be drawn from them. Thinking that there must be
some simple clue which would solve the whole problem, I com-
menced to work at the subject in the summer of 1878. At the
onset the clue was discovered, and the substance of the present
paper was written by the end of that year, before I had read for
the first time the paper of Mr. Bowman’s, in the ‘ Transactions’
of this Society. My astonishment was indeed great to find in
it the first glimmerings of my own opinions, for although the
subject had then been worked out but in the rough, and he had
a much simpler problem to deal with, yet undoubtedly he held
the same views in the main. My obvious course was, therefore,
entirely to rewrite my paper, making every acknowledgment to his
already published work. Mr. Bowman considered, as far as I can
make out, that the light stripe was to be compared with the
cement seen in longitudinal fibrillation between the fibrille, yet
he looked upon the striz as being due to the shape of the fibre.
From the history of the subject, which has just been given, it
will be seen that all observers are not agreed as to the actual
appearances of a striped fibre, and especially the changes which
occur during contraction, and we hold that they have fallen into
great and unwarrantable error in the conclusions (these, indeed,
are all contradictory) drawn from these appearances. A fibre
has been observed in the field of the microscope, which is marked
transversely, as already described, and all modern investigators
have concluded that the transverse bands mark the positions of
discs (seen on edge) of tissue of different refractive indices and
chemical composition, alternating in the long axis of the fibre.
This is, however, purely an assumption which in no way
follows.
We can also account for all these cross markings in a way
which involves no theory, and requires for its appreciation but a
knowledge of most elementary geometrical optics.
If a small fragment of muscle be teazed out in water, salt
solution, or almost any other fluid, and examined in the ordinary
way with a power of 300 diameters or more, the important fact
may be made out which is the basis of all these future observa-
tions, that the borders of the fibres are not smooth, but undulate,
presenting wavy margins (Fig. 1).
In the fresh unstained preparation there is a halo around the
edge of the fibre which masks this appearance, yet by carefully
adjusting the mirror so as to obtain oblique light, or by search-
ing fora fibre partly in the shade of another, the crenulated border
may be made out ; in the case of insects’ muscle this is, however,
always easy to demonstrate, for the fibres are much coarser, in-
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TIssuE. 815
deed, the appearance has been often figured in the works, even
of recent histologists. If the preparation be stained by any of
the ordinary dyes, perhaps most readily by picro-carmine, the
border is in all cases very distinct, and the regularly sinuous
margin is unmistakable. Now, what is the significance of the
wavy outline? It is, as will readily be understood, that the
fibre is ampullated, the wavy outline being but the optical ex-
pression of such a figure. A muscular fibre is, then, not a
smooth cylinder, but is like the turned leg ofa chair, or like the
transversely ribbed neck of a common water bottle in shape. If
the fibre be broken up into fibrille, which is very easy, after
maceration in alcohol, these are seen to have just the same cha-
racters ; indeed, a small bundle of fibrils is most convenient for
study. It may be well to remark that the ultimate fibrille often
show but little cross marking, and appear almost filamentous ;
that is, however, only due to their small size; a good lens will
bring out both points.
The above described appearances may be observed in all the
varieties of muscle that I have as yet examined, e.g. those ob-
tained from man, the dog, cat, rabbit, guinea-pig, mouse, frog,
mussel, crab, bee, wasp, Dytiscus, Hydrophilus, common house-
fly, &c., &c.
The transverse stripings of the fibre are related to and cor-
respond with the inequalities of the surface (Fig. 1). The little
elevations at the borders correspond, of course, to the little ridges
which run round the fibre, while the dips at the borders are the
optical expressions of little valleys running between them. In
the ordinary position the dark stripe marks the position of the
ridge, and the light stripe lies in the little valleys, as will be seen
on reference to fig. 1. ‘Then, again, Dobie’s line (Krause’s mem-
brane), which is a faint dark band in the very centre of the bright
stripe, runs along the bottom of the valleys (p in the diagram), and
Hensen’s stripe in the centre of the dark band, lies on the exact
summit of the ridges. (un, fig. 1.)
This position of the stripes in a normal muscular fibre is the
invariable rule, and the idea at once suggested itself, may not
the shape of the fibre itself cause the cross stripings ?
Any student of natural philosophy would at once affirm that
a structureless fibre of such a shape must be cross striped, and a
glance at the neck of the ribbed water bottle on the table will elicit
the same answer from any one.
The question we must now determine is, are the appearances
seen in the fibre just the same in all their details, as would be
produced by a piece of glass, or any other homogeneous trans-
parent substance of the same shape?
Before, however, entering into theoretical grounds, it may be
316 JOHN BERRY HAYCRAFT.
as well to give a full description of what is actually to be seen,
for this has yet not been stated.
With a structure of complicated figure, such as the one we
are considering, it is obvious that there is no one focus in which
it may be described. ‘There is one pretty definite focus for a
single speck or thin film, but even when examining a simple
cylinder, it is evident that when the borders of it are clear and
distinct, the upper surface is slightly out of focus. We shall
see, that in the case of the muscle, although there is one
position of the lens when the parts are very distinctly seen, and
in which they have mostly been described, yet that on slightly
altering the focus, the appearance is changed. These changes
we must carefully study.
For this purpose we may select the large muscles of the thigh
of arabbit; stretch them ever so little upon a piece of wood,
and place them for some days in 50 per cent. alcohol. A high
power is required for their examination; I have been in the
habit of using a 3; inch of Gundlach, a very perfect lens; a
=}; Inch will, however, do. A small bundle of fibrils should be
selected in preference to a whole fibre for examination.
On focussing it becomes at once apparent that on varying the
adjustment ever so little, you may bring into focus the tops of
the ridges or the bottoms of the valleys which lie between them.
Now this slight alteration is sufficient entirely to change the
optical appearances.
First raise the lens until the fibre be out of focus and is only
to be seen as a dim streak running across the field, then bring
it down until its form and the cross markings are distinctly to
be seen (the border is now not quite distinct on a level with the
horizontal axis of the fibre). In this position alternating light
and dark bands are made out, but no vestiges of Hensen’s
stripes or Dobie’s lines. (Fig. 3, a.) The dark band corres-
ponds with the valley and the light one to the ridge, or crest.
‘This was the focus in which Bowman described his preparations
as far as I can gather from the paper. If the lens be now
lowered ever so little, the stripes are reversed, a most curious
point, which was noticed by Bowman, but afterwards lost sight
of. The dark band now corresponds with the ridge, and the
bright band with the valley. (Fig. 3,c.) This is the focus-
sing in which it is usually described, and in this position Dobie’s
line and Hensen’s stripe are to be seen as a rule in uncontracted
fibres. .
Between these two positions of the lens there is generally a
well-marked intermediate one, which is depicted in Fig. 3, B.
The crests and valleys are both bright and equally so, although
‘the slightest movement of the fine adjuster will make either one
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE, 317
or the other the darker; on the slopes, as it were, there are,
however, narrow shaded bands, which are shown in Fig. 3, B.
The fibre is now quite clear and distinct, and the longitudinal
fibrillation is now best made out—if it can be seen at all—and
yet there is no sign of either Hensen’s or Dobie’s stripes.
These being the observed appearances (and they may be verified
without much trouble), we will calculate theoretically the
appearances which a homogeneous fibre of such a shape should
present when examined by transmitted light, so as to see
whether our observed effects tally with what may be theoretically
calculated. Parallel rays of light pass upwards through the fibre,
and in their course are altered in direction (see Fig. 4). The sub-
stance of the fibre being of higher refrangibility than the fluid in
which it is mounted, the thicker parts which correspond to the
ridges will act like converging lenses, causing the rays of light
to come to a focus (A A’ a”), diverging again. The thinner
parts (the valleys) will, on the other hand, act as diverging
lenses, causing the rays to spread out, as may be seen on refer-
ence to the diagram. Now it is evident that when the objective
is arranged to focus those rays which have passed through the
fibre and converge over the ridges, at that same position the
rays above the valleys will be diverging (see Fig. 4). This will
produce a difference in the appearance, for the converging rays
will give a bright band, while the position of those rays which
diverge will appear darker. Alter the focus by screwing the
lens up or down, and, provided the fibre can still be seen, this
state of matters will be reversed; for after converging, the rays
above, the position of the ridges will now be diverging, while at
the same time those over the valley will be converging and will
appear bright.
The condition seen in Fig. 3, 4, which is intermediate between
the low and high focussed picture of the fibre, would be obtained
by shifting the lens half way between these two positions.
Hensen’s stripe is no doubt due to rays passing through the
centre of the ridges suffering little refraction in their course,
and thus causing a brightness. Dobie’s line might, of course,
be the reverse of this, no rays at this point coming to the eye
of the observer; but we shall speak of this more hereafter, when
we shall show that there is some reason for suspecting at this
point a distinct structure.
Although it is indispensable to account theoretically for these
appearances, yet to most persons a simple demonstration will
carry more conviction than any proof deduced from the laws of
optics, however well they be understood. Instead of showing
“what should be,”’ we will study “ what is.”
For this purpose we will imitate as nearly as possible the
318 JOHN BERRY HAYCRAFT,
figure of a muscular fibre on a small scale, and it shall be made
out of a substance of uniform consistence throughout. What
appearances shall we see on microscopic examination? This has
been accomplished in the following manner: A glass rod is
Fic. 4.—This shows the passage. The convex parts converge the rays to
focus 4’ A” al”, after which they diverge. The lens shifted up or
down (vertically) over the ridges, and depressions will focus on the
retina alternately, converging and diverging rays.
heated in a spirit-lamp and plunged into a bottle of Canada
balsam ; it is then withdrawn, and a little drop of the balsam is
allowed to fall on a glass slide, or a thread of it may be laid out
on the surface of the glass. Before the drop or thread has
solidified it is indented with the milled head of a fine screw,
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 319
and examined with a power of from twenty to fifty diameters,
when cross shadings are to be observed. ‘These are seen, more-
over, to correspond with the surface impressions, and not only
so, but they are reversed on altering the focus. Hensen’s stripe
is generally very well seen. The most beautiful and convincing
object to study in this connection is a scale of the Lepisma.
They are oval in shape, transparent, and single refractile through-
out, and beautifully ribbed in their length, these ribbings or
groovings being indeed so fine that a power of at least 500
diameters will be required to make out those points to be here
described. You would think on looking at one of these scales
that a piece of muscle was flattened out before you on the field :
no rough balsam model, but a perfect illustration taken from
the back of a tiny insect.
The appearances it is needless to describe, for they are, almost
to the minutest detail, those of a muscular fibre. The bright
and dark stripe interchanging with every alteration of focus,
Hensen’s stripe, and Dobie’s line (Krause’s membrane) are all to
be seen. In the case of the Lepisma scale the line of Dobie
is in the centre of a bright band, which is broader than the
dark band with Hensen’s stripe. This is, of course, the other
way in the case of the muscular fibre.
We sce, therefore, that a muscular fibre presents just those
Fic. 5.—Muscular fibre described by Messrs. Geddes and Beddard.
Fic. 6.—On the right a nucleus is moulded on the fibre and is striped, the
stripes corresponding to the depressions on its surface.
Fie. 7.—This shows the muscular fibres of the heart.
appearances which a transparent body of uniform texture and of
similar shape would possess. However conclusive these proofs
3820 JOHN BERRY HAYCRAFT.
may have been, it is well to collect all evidence possible to show
that these markings are nothing more than optical effects, to
which end a very testing experiment was suggested to me by
Professor Tait. It is evident that if these cross bands are seen
when parallel, or nearly parallel, rays of light are passing through
the fibre, by using converging or diverging rays the appearance
will be altered, and it will be possible by careful adjustment of a
lens to cause a total reversal of the striping. If a fibre be care-
fully focussed and a strong biconcave diverging lens be placed
between the stage of the microscope and the mirror, and cate-
fully moved about with the fingers, it will be possible entirely to
alter the fibre, causing a total reversal of the cross bands. On
withdrawing the lens, of course the fibre resumes its normal
appearance. I may mention that several lenses were tried
before one was found which would in at all a satisfactory
manner show this phenomenon; when successful the experiment
is very striking.
In opposition to my view is the one generally accepted,
namely, that the cross stripings are produced by differences
along the fibre of chemical composition, and refrangibility.
Now, suppose that there were along the fibre two alternating
structures, A ands. Let a represent the bright stripe and B
the dark stripe. If a has a higher or lower refractive index
than B, it is evident that although they were immersed in any
number of fluids of refrangibility varying from the lowest to
the highest, yet a would always be distinguishable from B, and
the striping would always be apparent. Then, again, by placing
the fibres in fluids of indices near to that either of « or B, the
most striking would be the contrast. If, however, the fibre
were homogeneous throughout, the striping being merely due to
the form, then if the fluid and the fibre have the same refrac-
tive index all striping will disappear. On Professor Tait’s
suggestion, I tried a series of fluids formed by mixing, in
various proportions, alcohol, whose refractive index is low, with
oil of cassia, which is high. In this way I have prepared
specimens showing almost no cross striz, ‘the fibre appearing
uniform until after most careful examination.
Dr. Klein has since shown me some muscular fibres of an
insect. They were quite smooth and cylindrical, and were un-
striated. In these specimens there were, on very close exami-
nation, cross lines separated by comparatively wide intervals,
It is possible that they represented Dobie’s lines.
1 More recently my friends, Messrs. Geddes and Beddard have demon-
strated a very curious condition in the muscular fibres of the Echinus, which
my views entirely explain. They noticed that in the same fibre some parts
were cross striped, while in parts no striation was to be seen, Hearing of
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 321
But it may well be asked, What about the action of staining
agents, such as logwood, which is stated to tint the dark stripe
and Dobie’s line? Does this not show a difference of structure
along the fibres ?
Once having the clue it will be understood that just as the
unstained fibre will modify and change the direction of rays
passing through it, so will also a stained fibre produce what are
apparently modifications of the staining effect. It is generally
stated that the dark band and Dobie’s line are stained by log-
wood and carmine, while the bright bands remain unaffected ;
also that Hensen’s stripe in the centre of the dark stripe is
stained only to a slight degree; whence it follows that if stain-
ing action is to be the criterion, this stripe differs in structure
from the dark stripe.
We, however, affirm that the whole fibre is stained, and
equally stained throughout. The bright band is undoubtedly
stained, although it appears not of the deep blue of the dark
stripe when coloured by logwood; and this conclusion is drawn
not only from an examination of my own specimens, but also
from some of great beauty shown to me by Dr. Klein. Why
the bright band does not appear of so dark a blue is, that the
apparent shading of the latter is added to the blue tint, pro-
ducing a depth of colour. The most conclusive proof of this is,
that one can often reverse the colouring on readjusting the
focus, and that Hensen’s stripe or the bright part of the dark
stripe is only of a faint light blue, like that of the bright stripe.
Picric acid stains muscle very readily, and colours it through-
out. The fibre to the naked eye is yellow and uniformly
so, but when examined by the microscope, alternating yellow
and shaded yellow bands are to be observed, which reverse
their position on changing the focus. With a high focus—
when the crests are bright in the unstained preparation—they
are of a bright yellow, while the valleys are of a deeper yellow
tint.
To show the effects which a fibre of this shape can produce
when transmitting monochromatic light, nothing can be more
conclusive than the following experiment :—A slip of coloured
blue glass is held obliquely between the reflector and the stage
of the microscope, so that blue rays pass through the fibre. It
does not appear of a uniform tint, but beautiful blue stripes ase
seen corresponding with the crests and valleys, and varying with
alterations of focus. If a piece of red glass be substituted for
the blue slip, red cross stripes are seen in corresponding places.
my explanation of the markings, they re-examined their specimens (which
T have also seen), and found that when the stris were visible there, and
only there, the fibre was ampullated, (See Fig. 5.)
822 JOHN BERRY HAYCRAFT,
For this experiment the fresh fibres of insects’ muscle should be
examined, for, with fine mammalian muscle, the light is not so
good, owing to the higher power required. This experiment
has been introduced here with the description of stained muscle,
not that it can be strictly compared with an ordinary staining
process, but simply to show what an influence the fibre’s shape
must have upon the tinting, supposing, as we do, that this is in
reality uniform.
An investigation such as this is beset with many difficulties
and fallacies, and I may mention one which befel me in this
stage of my work.
I had stained a few muscular fibres of a rabbit with picro-
carmine, and on examination, what was my surprise to find that
in some of them the light stripes (valleys) were most brilliantly
stained with carmine. I was long puzzled at this, when it was
last discovered that the picro-carmine had dried somewhat on
the preparation, and the carmine had mechanically precipitated
along the valleys, filling them up. At the end of one or two
fibres this precipitation had partially peeled off, showing
undoubtedly the true nature of the phenomenon.
_ I have in my possession very beautiful alcoholic preparations
stained with logwood. At first sight, from a study of many of
the fibres, one would be led to beueve that the bright stripe is
wholly unstained, while the dark stripes are of a beautiful violet.
A careful examination, however, reveals the fact that such
fibres are broken up transversely, looking like piles of coins, a
very common occurrence, especially in preparations that have
been long mounted. The coins, lying close to one another,
with narrow chinks between, of course revealed transverse
unstained tracts, which could well be mistaken for the bright
stripe.
Mae interest and discussion has hitherto accrued to the
action of muscle on polarised light than to the effects of stain-
ing reagents. We have seen that much difference of opinion
exists; Briicke has maintained that not only is the dark stripe
(ridge), as all are agreed, doubly refracting, but that the whole
of the light stripe is isotropous. I myself was led to modify
this, discovering that on careful focussing with a fibre not at all
sheared in its length, the central part of the light stripe was
undoubtedly anisotropous. ‘This I have afterwards seen figared,
as before mentioned, in Hermann’s ‘ Physiology,’ and have
introduced the diagram into Fig. 2. It is a point of some
practical difficulty to mark exactly the positions of the cross
bands while turning the analyser, and thus changing the char-
acter of the field. ‘This difficulty has been overcome completely
by a suggestion of Professor Tait’s, who has helped me much in
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 323
this part of the work. Very fine emery powder should be
sprinkled over the preparation before covering it; for then, on
examination, numberless little black specks will be seen in the
field. A cross band of a fibre is selected for examination which
is exactly opposite one of these little specks, then when you
rotate you can definitely affirm, having the little black speck for
your guide, what change has occurred.
Rabbits’ muscles are very satisfactory objects for examination,
as they do not cleave across at all readily. The adductor muscles
of the leg should be excised, slightly stretched on a piece of wood,
and placed in 50 per cent. alcohol until they split readily into
fibrils. They may then be mounted in any ordinary fluid, a pinch
of emery powder having been sprinkled over the preparation
before covering.
It is necessary to use a power of 800 or 1000 diameters in the
investigation of mammalian muscle, while in the case of the insect
one of 800 diameters is quite enough.
In the living and dead muscular fibre the whole of its substance is
doubly refracting. The observations of some modern observers
entirely agree with my own, in that with crossed Nicols the
crests (dark bands) and the centres of the valleys (bright stripes)
appear bright and therefore refract light doubly, and that there
are two dark bands on the slopes between them (see diagram,
p. 5, Fig. 2). It does not foilow, however, that these two dark
bands represent tracts of isotropous substance. This is the point
at issue. The dark lines between the valieys and ridges which
appear when tie Nicols are crossed have been interpreted as
marking the positions of cross bands of singly refracting sub-
stance, but this is a fault of reasoning. Ifthe fibre were smooth
and cylindrical it would then follow, but the fibre is not, as we
have already insisted. These bands lie just on the sloped parts
of the fibre; those sections, in fact, which are oblique to the
passing rays; and the explanation is now quite easy, for the
extraordinary ray passing through the fibre is naturally deflected
at these parts, and does not reach the eye of the observer.
Hence the body appears not to transmit them at all at these
parts.
It is not difficult to explain the discrepancies between Briicke’s
description of the bright stripe and my own.
It is essential to be very scrupulous in the selection of a fibre
for examination. It must not be at all twisted, nor sheared in
the slightest degree, for then the cross stripes are not at right
angles to the long axis, and as their width 1s several times their
thickness (in the length) overlapping will to some extent occur.
This wilk certainly lead to very confusing results, and the bright
centre of the bright stripe (valley) may well he overlooked,
324 JOHN BERRY HAYCRAFT,
Moreover, the fibre should be slightly stretched, and as small as
possible.
It has also previously been mentioned that in many prepara-
tions the fibres split up transversely in a most regular manner,
and, unless the cover-glass be pressed upon, the little discs
remain in position with narrow chinks between them. These
chinks will be filled with the isotropous fluid used for mounting,
which will lead to very anomalous appearances, and which may
perhaps help to account for some of Briicke’s statements. These
fallacies may be avoided by a study of the fresh fibres of insects’
muscle. Dytiscus and hydrophilus muscle has received a large
share of the attention of histologists, but that from the wasp or
blue-bottle fly is quite as good. A leg should be pulled from
the trunk of a blue-bottle fly, and this again forcibly separated
at the middle joint. A piece of muscle will project from one of
the segments, which may be cut off and examined in a drop of
fluid expressed from the thorax of the fly. The polariscopic effects
may then be made clearly out in the still contracting fibres. I
have tested all these points by a careful examination of insects’
fibres with thin plates of selenite and mica. This method is not
so satisfactory, nor do the differences of colour seem to give
such reliable evidence as may be obtained by the crossed Nicols
alone.
The fibre during contraction.—Living insects’ muscle may be
examined and the changes observed when the waves of contrac-
tion pass along the fibre, or, perhaps better still, they may be
fixed with osmic acid. The muscles from the leg of an insect
are rapidly separated out on a slide, and a drop of weak osmic
acid added, which kills the fibres instantaneously, fixing them
in the position that they happen to be in. On examination one
generally finds fibres which in part of their course are contracted,
and in other parts relaxed, when the differences in appearance
may readily be studied. It may here be observed that the
fibres bulge at the contracted part, so that if the surfaces be
examined the focus of the microscope must be accommodated.
The cross stripes are nearer one to another and correspond, as
before, with the ridges and valleys seen at the margin, which are
much more prominent and bolder in outline.
In the contracted fibre the striping is practically the same as in
the stretched condition. The contracted fibre exhibits just the
same reversing of stripes on alteration of focus, and Dobie’s line
and Hensen’s stripe can both be seen in the same positions as in
the uncontracted muscle, provided the fibre is suitably placed for
‘examination, and not sheared in its length. We must entirely
deny the common statement, first introduced, we believe, by
Engelmann, that in the contracted state the bright band becomes
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE, 325
the darker. If good specimens of insects’ muscle be examined,
which have been treated with osmic acid, and if the fibre be not
sheared, the valley is always bright in the ordinary or deeper
focus. I have verified this point in very many cases. Passing
along a fibre from the relaxed end to a part where the contraction
is fullest, the appearances vary in degree, but not in kind. The
main features are in both cases the same, but the stripes are
now narrower, and often it is not so easy to see Dobie’s and
Hensen’s stripes. It follows, from the statement of Engelmann’s,
“the bright stripes become darker than the dim,” as he himself
notices that at one point, or phase, in the contraction, no striping
is to be made out. We agree with Ranvier that this is not
true ; indeed, it would be impossible for a muscular fibre with
its configuration not to be marked across its length.
This subject will call up to the mind of every working his-
tologist appearances which he must have met with in other fields
of research. Many tissues naturally, or after clumsy manipula-
tion, present ampullations which always coexist with cross striz.
The fibres of the crystalline lens are wavy in outline, and when
many of them are bound together and seen on edge with the
wavy outline towards the eye of the observer, cross bands are
seen which in chance preparations (especially those of the frog’s
lens) simulate muscle in a wonderful manner. Ordinary non-
striped muscle, which may be so well seen in the frog’s bladder,
is often faintly ampullated, especially, perhaps, in chloride-of-
gold preparations. Cross stripes may also here be seen. The
fibres of Tomes, when a section of softened tooth is teazed, are
pulled out of the dentinal tubules, and, being of a soft and some-
what elastic nature, on breaking they become often very beauti-
fully ampullated, and it would be impossible to distinguish them
from muscular fibrille. In the class of practical histology, on
more than one occasion students have asked me the meaning
of beautiful cross shadings seen on nerve fibres; a slight
ampullation, which fully accounted for it, was always found.
Many more instances of a like nature will be recalled in the
experience of every one; it is needless to enumerate further.
In the winter of 1879-80, while examining fibres of the
muscles of a newly-born child, a very curious: discovery was
made. A nucleus adhering to the sarcolemma was seen beau-
tifully striped. It was not in close apposition to the fibre, a very
narrow chink intervening. On focussing with great care, it
was seen that the cross bands upon it corresponded with those
of the adjoining fibre, a dark one, however, for a light one, and
vice versa (fig. 6). Now, the curious point was that the nucleus
had evidently been impressed by the fibre, moulded upon it,
as it were, and on being pulled apart had presented a perfect
326 JOHN BERRY HAYCRAFT,
cast of the surface. One would hardly believe in sarcous
elements here. Last summer (1880) my friend Mr. Priestley
communicated to me a similar and independent observation of
his own, as a contribution towards the maintenance of my views
upon the formation of the stripes.
The position that we have reached is this:—A muscular fibre
presents such cross markings, varying with shifting the lens up
or down, as a filament of homogeneous structure and similar
shape. I have shown this experimentally, and have illustrated
with simple experiments, which it is in the power of any one to
test. This being the case, I have searched to find if there be
reason to assert any want of uniformity along the fibre, using
various methods of staining. ‘This I have failed to do, and have
shown that the views commonly held are to be explained simply
by the shapes of the fibres. As to the action of muscle on
polarised light, I saw reason to dissent from the views of
Briicke, and subsequently found my own in accordance with
those of other recent observers. I differ from them in the ex-
planation I offer of the two dark bands seen with crossed Nicols,
for here, again, the shape of the fibre explains their presence
without looking for any special structure.
So far we are led to consider the fibre as made up of many
ampullated fibrils, packed side by side, forming an ampullated
fibre, these fibrils being uniform throughout, and joined together
by some cementing material, the nature of which we will not
hazard. The only point which would suggest a definite structure
along the fibril is the attachment of the sarcolemma in insects’
muscle to Dobie’s lines. There is no doubt that this membrane
dips down and seems prolonged into Dobie’s lines in a most
beautiful and regular manner. The significance of this is very
obscure, and is quite beyond me. ‘There are many possibilities.
It may be, although there is no proof of it, that a membrane
exists here continuous with the sarcolemma; it may be that there
is nothing but some cementing substance more soluble in alcohol
than the sarcous matter; it may be that there is a little minor
crest at this point to which the sarcolemma is attached. This
little crest I have certainly seen in some fibres, and it has
already been figured by more than one writer, yet in others,
whose outlines are wonderfully distinct, no trace of it is to be
made out. ‘The fibres can hardly be said to break across in
the line of Dobie; all that can definitely be affirmed is that
they cleave in the thinnest part, or the light stripe. The in-
vestigation of this point is one of great difficulty, owing to the
haze around the broken points, and I can never make up my
mind to any definite statement. This transverse cleavage is not,
of course, a point of very much weight, as the fibre would
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 327
naturally tend to split across in or near Dobie’s lines, as here it
is thinnest.
The striping of muscle can be easily explained, as shown
before, which leads us to our final statement. A fibril is struc-
tureless throughout its entire length, except that, perhaps, there
may be membranes, or lines of fission, or layers of cement at
the positions of the lines of Dobie; this we leave an open
question. In using the word “structureless,” I must not be
misunderstood ; structureless membranes and tissues are fast
losing their place in histology, and once simple protoplasm is
now most complex. What I infer is that the stripes do not
mark the positions of alternating layers of different structure,
the presence of which are ordinarily maintained. The compli-
cated Muskelkistchen of the Germans does not exist.
The muscular tissue of the heart presents many peculiarities
which it is needless here to enumerate, for the cross striping
alone concerns us. All those cross bands which have been de-
scribed in ordinary voluntary muscle may here also be seen,
and they are placed in the same relations with the turned surface
of the fibre. The dark stripe corresponding to the crests, or
ridges, the light bands to the depressions between them. (Fig. 7.)
Dobie’s lines may be made out with great ease, and as there is
no sarcolemma here, they may be accounted for also purely
from the shape of the fibres. I have often thought that Dobie’s
lines marked the positions of tiny ridges in the valleys, but this
is a point more difficult to decide perhaps than in the case of
the skeletal muscles. Transverse cleavage takes place here also
in the thinner part of the fibre, namely, in the bright stripe,
but whether or not exactly in Dobie’s line I have not yet definitely
made out.
A curious appearance, often presented by insects’ muscle, and
sometimes also by that of the mammalia, has been described and
figured by Mr. Schiifer. A paper descriptive of these he com-
municated to the Royal Society of London (1873), which came
out later on in the ‘Transactions’ of this Society, and his
observations are published also in the eighth edition of Quain’s
‘Anatomy.’ These have been almost entirely overlooked by
French and German physiologists, yet in many English labora-
tories his observations have been verified, and his conclusions
taught.
They are well illustrated in a representation of the muscular
fibre of a Dytiscus, which may be seen in Quain’s ‘ Anatomy.’
The dark stripes are traversed longitudinally by dark rods, which
end at both extremities in little knobs. These knobslie in the border-
land between the bright and dark stripes. The only point which
I would add to his figure is this, that the knobs are joined across
828 JOHN =SRRY HAYCRAFT,
the clear stripes or valleys by lines, just as they are so joined
across the dark stripes, although the lens must be depressed
ever so little to make this out. These lines are, in fact, nothing
more or less than the longitudinal strize described many years ago
as lying between the fibrillee of which the fibre is composed,
these little knobs lying in their course. This can, perhaps,
most conclusively be made out in the following way :—Allow a
piece of insect’s muscle to remain in a drop of water for some
hours (which will vary with the temperature) until it has par-
tially putrefied. Then cover and examine, when many of the
fibres will have separated towards their ends into fibrille. One
can then distinctly trace the chinks between the separated fibrillee
as being continuous with the striz, on which the knobs are still
seen in the centre of the fibre. I think that the following is a
feasible explanation of these knob-like enlargements of the
cementing substance seen as longitudinal strie. These knobs
occur, as will be beautifully seen on referring to the woodcut in
Quain, on the slopes between the valleys and the ridges. The
cementing substance dips down here with the fibre itself, and if
there be the slightest lateral obliquity it will appear larger.
You see the cementing matter on edge, and differing as it does
from the muscle-substance in refrangibility, a distortion occurs,
giving rise not toa dark line as on the surface, but to a dark knob.
This is, in fact, but an optical delusion, for the striz are quite
uniform, and were the fibre cylindrical would appear so. This
may be proved by the fact that very often if the rays of light
from the reflector are oblique, but one set of dots appears, which
shift over to the other side on twisting the mirror. By shifting
the preparation about, or by twisting the tube of the microscope
obliquely, the dots disappear from one part of the fibre to appear
in another, showing that it is but an optical effect, and that no
structure here exists.
Before concluding I must gratefully acknowledge much help
and sympathy which I have received in this investigation.
To Professor Tait I have gone when in any difficulty, for an
observer in a case such as this must have the aid of an ex-
perienced physicist, otherwise grievous error is but courted. To
him, as has been seen in the text, I owe many suggestions, and
he has kindly entirely looked over my paper. Dr. Klein has
shown me great kindness in carefully examining wy preparations
from the histological point of view, and as has before been men-
tioned, in showing me preparations to corroborate my views.
My thanks are due to my friend Mr. Priestley for many useful
hints, especially concerning the literature of the subject.
CAUSE OF STRIATION OF VOLUNTARY MUSCULAR TISSUE. 329
Addendum.—An assertion has been lately made which if
true would be entirely fatal to my views. It was, that in the
fresh condition the fibres are cross striped, but at the same
time their borders are quite smooth. That this is erroneous is
easy of demonstration with any fresh fibre, but especially with
that of an insect. It is true that often from the manipulation,
or their own contraction, they are twisted, when the convex
border will on a careless inspection appear as a distinct line.
The stripes at this point are not at all distinctly seen, but yet can
always be made out, as well as the crenulated border. Indeed,
this has been figured by more than one observer (Krause), and
it was in the fresh muscle of the crab that I first observed it.
Dr. Klein informs me that there is no doubt as to the transi-
tional stage in the contraction of a muscle described by Engel-
mann. It will be remembered that this is intermediate between
the contracted and relaxed part, and that here the fibre is non-
striated. Dr. Klein from a study of one of Hnglemann’s pre-
parations was able to give the true explanation of this. The
part which was non-striated was perfectly smooth in outline,
passing at either end into the striped and crenulated fibre.
Probably the intermediate part is a piece of the fibre stretched
by its contraction, the two ends being fixed.
VOL. XXI.—NEW SER, ¥
330 PROFESSOR JOSEPH LISTER.
On the Reiation of Micro-oreanisms to Diszase. By
JosEPH Lister, F.R.S., Professor of Clinical Surgery
in King’s College, London.!
Tue relation of micro-organisms to disease is a subject of
vast extent and importance. If we compare the present
state of knowledge regarding it with that of twenty years ago,
we are astonished at the progress which has been made in
the interval. At that time bacteria were little more than
scientific curiosities; whether they were animal or vegetable
few people knew or cared, but most regarded them as animals
on account of the active movements which they often ex-
hibited. That they were causes of’ putrefaction, or other
fermentative changes, was a thing scarcely thought of; and
the notion that they had special relations to disease would
have been regarded as the wildest of speculations. Now,
however, a mass of information has been accumulated re-
garding all these points, of which it would be hopeless for
me to attempt to give even a brief sketch in the time at my
disposal, and all that I can do is to present to the pathlo-
logical section a few examples illustrating the progress which
is being made in this department of research.
First, I will mention some examples of the labours of Dr.
Koch, of Wollstein, in Germany. Though a hard-worked
general practitioner, Koch has contrived to devote an im-
mense amount of time and energy to his investigations, and
by a combination of well-planned experiments, ingenious
methods of staining bacteria out of proportion to the tissues
among which they lie, a beautiful adaptation of optical
principies to render the coloured objects discernible by the
human eye, and, further, by a most successful application
of micro-photography, he has succeeded in demonstrating
the presence of these minute organisms in a manner never
before attained.
The Bacillus anthracis is now universally recognised
among pathologists as the cause of splenic fever, so fatal
among cattle in this and other countries, and capable of
being communicated to various other animals, and, among
the rest, to the human species, as has been lately illustrated
by the so-called woolsorters’ disease, in the North of
England. The Bacillus anthracis is a large form of bacte-
1 An address delivered before the Pathological Section of the British
Medical Association at Cambridge, August 12th, 1880.
THE RELATIONS OF MICRO-ORGANISMS TO DISEASE, 331
rium, as is shown at @ in the accompanying woodcut. It is
( ~
oe _) F yy
there represented magnified 700 diameters, along with red
blood-corpuscles of a mouse, and the rods of which it is
composed are seen to be in diameter nearly one fourth of
that of the red corpuscles. Koch’s method of staining the
sections shows in the most beautiful manner that these
bacilli are not only present in the spleen and some other
organs, but that they people the blood in the minute vessels
of all parts. Koch has thus added to our conviction that
the bacillus is the cause of the symptoms, seeing that, as he
remarks, it is impossible to suppose that an organism can
develop in such enormous numbers at the expense of the
vital fluid without exerting a serious influence upon the
system.
But the most striking and important results of Koch’s
methods of investigation are those which relate to organisms
of much smaller dimensions. He found that, if putrid
liquid is injected under the skin of a mouse, the animal
may die in the course of a short time, as the result of the
chemically toxic effects of the products of putrefaction ab-
sorbed into the circulation; but, if it survive this primary
disorder, it may succumb in the course of about two days to
blood disease. If the point of a lancet be dipped into the
blood of the heart of a mouse which has died in this way,
and a scratch be made in the skin of a healthy mouse with
the envenomed instrument, the second mouse dies with
similar symptoms to those of the first, the poison being
absolutely certain in its virulent operation; and the same
thing may be continued indefinitely through any series of
animals. If now sections of the tissues be made and stained,
and examined by Koch’s procedures, it is found that the
entire blood of the diseased animal is peopled with bacteria,
resembling those of the Bacillus anthracis in the enormous
multitudes in which they are produced, and also in their
rod-like form, but differing from them in being exquisitely
minute and delicate, as is shown at 6 (drawn on the same
scale as @, as is indicated by the accompanying outlines of
red corpuscles), where it is seen that the diameter can only
332 PPOFESSOR JOSEPH LISTER,
be represented by a slender streak not one eighth of the
diameter of the Bacillus anthracis, and such as, before the
introduction of Koch’s method, would have escaped notice
altogether. Now, this disease is totally distinct from pyzmia,
being not accompanied with multiple abscesses or embolism;
and thus it has been shown by Koch that septicemia may
© )
ree
:
OO
exist as a deadly blood disease, caused by the development
of micro-organisms, equally distinct from pyemia and from
the chemically toxic effects of septic products.
On some occasions, as the result of the introduction of
putrid fluid under the mouse’s skin, Koch found, besides
septicemia, a local affection of the seat of inoculation, in the
form of spreading gangrene; and, on investigating the part,
he discovered in it, exactly corresponding with the extent of
the local affection, another organism very differently formed
from that of the septicemia, viz. a micrococcus, consisting
of minute spherical granules arranged in linear series, like
strings of exquisitely minute beads, as represented at ¢ in
>
the woodcut. Believing that this locally developing or-
ganism must be the cause of the gangrene, he tried to sepa-
rate it from the bacillus of the septicaemia, and succeeded
through an accidental observation of great interest. Having
till that time employed the house mouse in his experiments,
he happened to try the inoculation of a field mouse. This
animal, though so closely allied, proved not susceptible of
the septicemia. The bacillus of that disease was unable to
grow in the blood of the field mouse, but the micrococcus of
the gangrene could develop among its tissues. The new
organism was thus obtained in an isolated form, and, when
now inoculated into the house mouse, produced in that
animal gangrene pure and simple, extending for an inde-
finite period among its tissues.
Thus the animal body, which had previously been an
obscure field of labour in this department, in which the
THE RELATIONS OF MICRO-ORGANISMS TO DISEASE, 339
pathologist did little more than grope in the dark, was con-
verted by Koch into a pure cultivating apparatus, in which
the growth and effects of the micro-organisms of various
infective diseases could be studied with the utmost sim-
plicity and precision.
One more example I must take from Koch’s work. On
one occasion, as the result of inoculating putrid liquid into
a rabbit, he observed a spreading inflammation having all
the clinical characters of erysipelas; and, on examining
stained sections of the part, he discovered another exqui-
sitely delicate bacillus resembling the micrococcus of the
gangrene in being local in its development, while its exact
correspondence in extent with that of the disease led fairly
to the conclusion that it constituted the materies morbi.)
I will next refer to a disease occasioned by a micro-
organism discovered by the eminent pathologist, Professor
Toussaint, of Toulouse, whom I am proud to see present in
this Section to-day. This disease has been somewhat in-
appropriately termed Cholera des poules, or fow) cholera,
for it is not attended with diarrhoea or any other of the
symptoms of cholera; but, as it happened to be extremely
destructive among the poultry-yards of Paris at the same
time that an epidemic of cholera was raging in the city, the
disorder that prevailed among the fowls was also given the
name of cholera. The lesions by which it is chiefly cha-
racterised are great swelling of the chains of lymphatic
glands in the vicinity of the trachea, pericarditis accom-
panied with great effusion, and congestion, and it may be
ulceration, of the mucous membrane of the duodenum. It
is a blood disease, and highly infectious. If some of the
blood of a chicken that has died of it be mixed with the oats
with which healthy chickens are fed, a considerable propor-
tion, perhaps four out of six, are affected and die; and
similar results are produced by mixing the intestinal ex-
creta of diseased fowls with the food. It is an interesting
question how the virus thus administered enters the circu-
lation. The invariable affection of the lymphatic glands of
the throat suggests to M. Toussaint the idea that some
accidental abrasion of the epithelium in the mouth or
pharynx is probably the channel; and this view is con-
firmed by the fact that a similar affection of the lymphatic
glands, together with other symptoms of the disease, is pro-
duced by inoculating the chicken in the mouth; and fur-
‘See ‘Untersuchungen iiber die Atiologie der Wundinfectionskrank-
heiten, von Robert Dr. Koch, Leipzig, 1878. . A translation has just been
issued by the Sydenham Society.
334 PROFESSOR JOSEPH LISTER.
ther, by the circumstance that such chickens as fail to take
the disease when fed with the infected food are liable to it
when inoculated, implying that it was merely some acci-
dental circumstance which secured their previous immunity.
This disease has been made the subject of special investiga-
tion by M. Pasteur. He found that the micro-organism
could be readily cultivated outside the body of the fowl. It
was, indeed, somewhat particular as regards the fluid in
which it would grow; thus yeast-water, in which the
Bacillus anthracis grows readily, proved an unsuitable
medium for this organism, but it grew luxuriantly in
chicken broth, and, indeed, in infusion of other kinds of
meat; but chicken broth proved peculiarly convenient for
the purpose. M. Pasteur has been so kind as to send me
some tubes in which the organism has been cultivated, and
a drop of the liquid has been placed under a microscope on
the table. It will be seen that the organism is a minute
form of bacterium, oval-shaped, tending to multiplication by
transverse constriction, and very frequently seen in pairs,
and occasionally in chains. Its transverse diameter is from
1-50,000th to 1:25,000th of an inch, so that it resembles very
closely the Bacterium lactis. The woodcut d represents a
camera lucida sketch of the organism sent by M. Pasteur.
So far as I am aware, this is the first time this bacterium
has been shown in this country. Now, it was found by
Pasteur that the organism could be produced in chicken
broth in any number of successive cultivations, and to the
last retain its full virulence, so that, if a healthy chicken be
inoculated with it, the fatal disease was produced as surely
as by inoculation with the blood of a fowl that had died of
the complaint. This was pretty conclusive evidence that
the organism was the cause of the disease, and that it con-
stituted the true infective element ; because any other mate-
rial that might be supposed to accompany it in the blood of
the diseased animal must have been got rid of by the suc-
cessive cultivations in chicken broth.
The growth of the organism occasions no putrefaction in
the liquid; so that this is a good example of a bacterium
which is most destructive as a disease, but which is at the
same time entirely destitute of septic property, in the primi-
tive sense of that term as equivalent to putrefactive. After
THE RELATIONS OF MICRO-ORGANISMS TO DISEASE, 335
the bacterium has grown for a certain time in a given por-
tion of chicken broth, it ceases to develop further ; and when
this is the case, although the broth has lost only a very
small proportion of its substance by weight, and although,
as aforesaid, it has not undergone putrefaction, and still
constitutes an excellent pabulum for ordinary forms of
bacteria, the bacterium of the fowl-cholera, though intro-
duced from some new source, is incapable of growing in it.
This fact seems highly suggestive of an analogy with the
effects of vaccination, or those of an attack of measles or
scarlatina in securing immunity from the disease for the
future. Here we have a certain medium invaded by a virus
capable of self-multiplication, as is the case with those dis-
eases in the animal body; the medium itself little affected
chemically by the growth of the virus within it, but never-
theless rendered unfit for the development of that virus for
the future. But something more than the suggestion of
analogy with vaccination has been effected by M. Pasteur.
By cultivating this bacterium in a particular manner, which
he has not yet published, he enfeebles the organism, as he
believes, and produces such an alteration in it that, when
inoculated into a healthy fowl, it produces only a modified,
and no longer fatal form of complaint, but the bird is
thereby rendered secure against taking the ordinary form of
the disease. It has been really vaccinated, if we adopt M.
Pasteur’s extension of the term vaccination to other similar
cases ; for just as we speak of an iron milestone, we may, if
we please, apply the term vaccination to the use of a virus
other than the vaccine obtained from a heifer. But though
the vaccination with the modified bacteria of the fowl-
cholera does not occasion the fatal disease, it produces
pretty severe local effects. If inoculated on the breast of
the fowl, it causes a limited gangrene of the pectoral muscle,
the affected part falling off in due time as a dry slough.
Through the great kindness of M. Pasteur, I have now the
opportunity of showing to the Section a hen which has
been treated in this way. You observe a slough on the
breast of the bird about as large as a penny piece ; it is dry,
and obviously old. The fowl has been some days in my
possession subsequently to its journey from Paris; but
though more than enough time has elapsed since the inocu-
lation to have caused its death, had the dieease been in the
ordinary form, it is, you see, in good health, bright and
active, and it both eats and sleeps well.!
' M. Pasteur’s researches on this subject are related in the ‘Comptes
Reudus de l’ Académie des Sciences,’ February, April, and May, 1880.
336 PROFESSOR JOSEPH LISTER,
I will now return to the Bacillus anthracis, with regard
to which I shall have again to refer to the labours of M.
Toussaint. First, however, I must allude to the work of
some of my own countrymen. In March, 1878, an experi-
ment was made at the Brown Institution, at the suggestion
of Dr. Burdon Sanderson, of inoculating a calf with the
blood of a guinea-pig which had died of splenic fever, which
is exceedingly fatal to rodentia. The result was that the
calf took the disease, but in a mild form, and recovered
from it; and a similar fact was observed in two heifers
treated in the same way.
This line of inquiry has since been followed up by Dr.
Sanderson’s successor at the Brown Institution, Dr. Green-
field, with a view of ascertaining whether the milder form of
the disease in cattle, resulting from inoculation with the
blood of rodentia affected with it, confers upon the cattle
immunity from the complaint in its fatal form; or, to use
again M. Pasteur’s expression, whether the cattle have been
vaccinated with reference to anthrax. And I have great
pleasure in being able to inform the Section, by Dr. Green-
field’s permission, that the question has been answered in
the affirmative; and that one bovine animal, inoculated
seven months ago with virus from a rodent, has proved
itself, on repeated inoculations, entirely incapable of con-
tracting splenic fever, remaining free from either constitu-
tional or local manifestations of it.
And now to return to M. Toussaint, who has made obser-
vations with regard to this same subject of vaccination
against anthrax fraught with the very deepest interest.
The question arises with regard to effective vaccination,
using the term in Pasteur’s general sense: Is it essential
that micro-organisms should develop in the blood of the
animal in which immunity from further attacks of the dis-
ease is to be secured? Or is it possible that the necessary
influence upon the system may be exerted by merely chemi-
cal products of the growth of that organism in some other
medium? With the view of approaching the solution of
this question, M. Toussaint has performed experiment of
injecting into the blood of healthy sheep blood taken from
an animal affected with splenic fever, but deprived of the
Bacillus anthracis. Taking blood from a sheep just on the
point of death, when the bacillus has presumably produced
all its possible effect upon the vital fluid, M. Toussaint pro-
ceeds to deprive it of the living bacillus in either of two
1 See “ Report on Experiments on Anthrax,” by Dr. Sanderson (‘ Journal
of the Royal Agricultural Society of England,’ vol. xvi, s.s., part i).
THE RELATIONS OF MICRO-ORGANISMS TO DISEASE. 337
ways—by filtration, or by destroying the vitality of the
organism. The former he effects by mixing the blood with
three or four parts of water, and then passing it through
about twelve layers of ordinary filter-paper. ‘The bacillus,
in consequence of its large dimensions, is entirely retained
by this form of filter, as is proved by the fact that the
filtrate no longer gives rise to the organism in a cultivating
liquid or in a living animal. Nevertheless, if injected in
considerable quantity into the circulation of a healthy sheep,
it produces a true vaccinating influence, that is to say,
secures immunity from splenic fever. But, what is further
extremely interesting, in order that this change in the con-
stitution of the sheep may be brought about, the lapse of a
certain time is essential. If a vaccinated sheep be inocu-
lated with anthrax within a few days of the operation, it
will die of splenic fever ; but if from twelve to fifteen days
be allowed to elapse, complete immunity is found to have
been produced. Similar results followed from the injection
of anthrax blood treated by Mr. Toussaint’s other method,
which consists of maintaining it for a considerable time at
a temperature of 55° C. (131° F.), which has the effect of
killing the bacillus; after which one half per cent. of car-
bolic acid is added, to prevent putrefaction of the liquid.
The blood treated in this way having been proved to be
free from living bacilli by negative results of an experiment
upon a rodent, about four cubic centimétres are injected into
the venous system of a sheep, with the effect of producing
the same protective influence against splenic fever as is
ensured by the filtered blood. ‘These experiments are still
in progress; but M. Toussaint informs me that he has
already ascertained the existence of immunity against an-
thrax for three months and a half in both sheep and dog
treated in this way.
I need hardly remark on the surpassing importance of
researches such as these. No one can say but that, if the
British Medical Association should meet at Cambridge again
ten years hence, some one may be able to record the dis-
covery of the appropriate vaccine for measles, scarlet fever,
and other acute specific diseases of the human subject. But
even should nothing more be effected than what seems to be
already on the point of attainment, the means of securing
poultry from death by fowl-cholera, and cattle from the
terrible destructive splenic fever, it must be admitted that
we have an instance of a most valuable result from the much-
reviled vivisection.
I have yet one more example to give of researches in this
338 PROFESSOR JOSEPH LISTER.
domain of pathology; and this also has reference to the
Bacillus anthracis. ‘The investigator in this instance is Dr.
Buchner, assistant physican in Munich. It is well known
that the Bacillus anthracis is morphologically identical with
an organism frequently met with in infusion of hay,
which may be termed hay-bacillus. Such being the case, it
occurred to Dr. Buchner that they might be merely one
and the same organism modified by circumstances. For my
own part, I am quite prepared to hear of such modifying
influence being exerted upon bacteria, having made the
observation several years ago that, when the Bacterrum
lactis had been cultivated for some time in unboiled urine,
it proved but a feeble lactic ferment when introduced again
into milk. Its power of producing the lactic fermentation
had been impaired by residence in the new medium. In the
case before us, indeed, the physiological difference between
the two organisms seems, at first sight, so great as to forbid
the idea of anything other than a specific difference. The
Bacillus anthracis refuses to grow in hay-infusion, in which
the hay-bacillus thrives with the utmost Inxuriance; and
conversely, the hay-bacillus is utterly incapable of growing
in the blood of a living animal, whether introduced in small
or in large quantities. ‘The hay-bacillus is remarkable for
its power of resistance to high temperatures, which is not
the case with the Bacillus anthracis. The latter is destroyed
by a very slight acidity of the liquid of cultivation, or by
any considerable degree of alkalinity, whereas the former
survives under such conditions. Both will grow in diluted
extract of meat, but their mode of growth differs greatly.
The hay-bacillus multiplies rapidly, and forms a dry and
wrinkled skin upon the surface, while the Bacillus anthracis
produces a delicate cloud at the bottom of the vessel, in-
creasing slowly. Nothing daunted by these apparently
essential differences, Dr. Buchner has laboured with indo-
mitable perseverance, by means of experiments carried on
in Professor Nageli’s laboratory, to solve the double problem
of changing the Bacillus anthracis into hay-bacillus, and the
converse. Having devised an ingenious apparatus by which
a large reservoir of pure cultivating liquid was placed in
communication with a cultivating vessel, so that any culti-
vation could be drawn off by simply turning a stop-cock,
and further cultivating liquid supplied to the organisms
remaining in the vessel by a mere inclination of the appa-
ratus, Buchner proceded to cultivate the isolated Baczllus
anthracis in extract of meat for several hundred successive
generations. As an early result of these experiments, he
THE RELATIONS OF MICRO-ORGANISMS TO DISEASE. 339
found that the bacillus lost its power of producing disease in
an animal inoculated with it. Up to this point he is con-
firmed by Dr. Greenfield, who has found that, when the
Bacillus anthracis is cultivated in aqeous humour, after about
SiX generations it loses its infective property. Then as
Buchner’s experiments proceeded the appearance of the
growing organism was found to undergo gradual modifica-
tion. Instead of a cloud at the bottom of the vessel, a
scum began to make its appearance-—at first greasy-looking
and easily broken up—constituting, so far as appearances
went, an intermediate form between the two organisms ; and
in course of time the scum became drier and firmer, and at
length the modified Bacillus anthracis was found to be
capable of growing in an acid hay infusion, and to present
in every respect the characters of the hay-bacillus. The
converse feat of changing the hay-bacillus into the Bacillus
anthracis proved very much more difficult. A great number
of ingenious devices were adopted by Buchner, who was,
nevertheless, continually baffled, till at last he attained suc-
cess in the following manner :—Having obtained the blood
of a healthy animal under antiseptic precautions, and defi-
brinated it also antiseptically, and having arranged his
apparatus so that the pure defibrinated blood, which was to be
the cultivating medium, should be kept in constant move-
ment, so as to continually break up the scum, and also keep
the red corpuscles in perpetual motion so as to convey
oxygen to all parts of the liquid—in this way imitating, to
a certain extent, the conditions of growth of the Bacillus
anthracis outside the animal body, within which the hay-
bacillus could not be got by any means to develope—he
proceded to cultivate through numerous successive genera-
tions. A transitional form soon made its appearance; but
the change advanced only toa limited degree, so that further
progress by this method became hopeless. The modified
form hitherto obtained failed entirely to grow when injected
into the blood of an animal. On the contrary, it was in a
short time completely eliminated from the system, just like
the ordinary hay-bacillus. It had, however, been observed
by Buchner that spores had never been formed by the
bacillus growing in the defibrinated blood; and it occurred
to him that, perhaps, if it were transferred to extract of
meat, and induced to form spores there, the modified
organism might yet grow in the blood of a living animal.
The carryiug out of this idea was crowned with success ;
and, by injecting various different quantities of the liquid
containing the organism into different individuals, Buchner
340 PROFESSOR JOSEPH LISTER.
at length succeeded, both in the mouse and in the rabbit, in
developing true Bacillus anthracis out of the progeny of the
hay-bacillus. When large quantities were introduced, the
animals died rapidly from the merely chemical toxic effects
of the injected liquid; but, in some instances in which a
smaller amount was injected, after the period for these pri-
mary effects had passed, a fatal disease supervened—attended,
as in anthrax, with great swelling of the spleen, the blood
of which was found peopled, as in that affection, with newly
furmed bacilli; and the spleens affected in this way were
found to communicate anthrax to healthy animals, just
like those of animals which have died of ordinary splenic
fever.)
Supposing these results to be trustworthy (and the record
of them bears the stamp of authenticity) I need scarcely
point out tou a meeting like the present their transcendant
importance as bearing upon the origin of infective diseases,
and their modifications as exhibited in epidemics.
I trust that these examples may suffice to convey some
idea of the work now going on with reference to the rela-
tions of micro-organisms to disease.
Since the address was delivered M. Pasteur has published
the method by which he produces the “ attenuation ” of the
virus, or in other words, the enfeeblement of the organism of
fowl-cholera which fits it for securing immunity from the
fatal form of the disease. This method consists in cultivat-
ing the organism, pure and nnmixed,in chicken broth, to
which access of air is permitted while dust is excluded, and
simply allowing some months to elapse before it is employed.
If the period does not amount to more than about two
months, the organism retains its virulence little abated, but
if the period is extended to three or four months it is found
that animals inoculated with the organism take the disease,
but have it in a milder form, and a considerable proportion
recover ; and if the time is made still greater, as, for ex-
emple, eight months, the organism has so far lost its potency
that though chickens inoculated with it still go through an
attack of the disease all recover. If the period is sufficiently
prolonged, there comes a time when the organism is found
to have lost its vitality altogether, so that it will no longer
give rise to new development when introduced into fresh
cultivating liquid.
In considering by what agency this enfeeblement of the
organism and ultimate extinction of its vitality was brought
1 See ‘ Ueber die experimentelle Erzeugung des Milzbrandcontagiums
aus den Heupilzen,’ von Hans Buchner, Miiuchen, 1880.
THE RELATIONS OF MICRO-ORGANISMS TO DISEASE, 341
about under the circumstances referred to, it occurred to M.
Pasteur that it might perhaps be the oxygen of the air
admitted to the vessels. Oxygen is essential to the growth
of the organism, but it might, as M. Pasteur thought, be,
nevertheless, in long-continued action upon it, a cause of
weakness. With a view of testing this idea he instituted culti-
vations of the bacterium in broth contained in tubes partially
filled with the liquid, that is to say, containing a certain
proportion of their volume of air, but sealed hermetically.
The result was a growth of the organism, indicated by tur-
bidity of the clear fluid, attaining a degree proportioned to
the amount of air present in the tube, but soon coming
to an end when that air was exhausted, so that the little
organism, no longer growing throughout the liquid, fell to
the bottom of the vessel, leaving the fluid again clear. The
organism having now exhausted all the free oxygen, was
from this time forth presumably protected from the influence
of that element, and, in exact accordance with M. Pasteur’s
theory, it was found that no matter how long these closed
tubes were kept, the organism retained not only its vitality,
but its full virulence, as tested by inoculation of healthy
chickens.!
These facts are certainly fraught with the deepest interest,
and the medical world must for ever remain deeply indebted
to M. Pasteur for eliciting them. Doubts may, however, be
entertained regarding the interpretation of the phenomena.
Thus Dr. Greenfield, whose own researches have had special
reference to the modifying influence exerted upon bacteria
by the medium in which they grow, has thrown out the
suggestion that the enfeeblement of the organisms of fowl
cholera grown with free access of air may be due to altera-
tions in the fluid which they inhabit rather than to the
effect of oxygen upon them. When free access of oxygen is
permitted, the organism, he contends, will continue to grow
till all the material suitable for its nutrition is exhausted,
and as the nutriment becomes defective the progeny will be
feeble. At the same time this exhaustive development of
the organism will be attended by the full measure of possible
alteration in the quality of the liquid which the growth of
the organism can effect, and this alteration will naturally
involve the production of substances which may exert a
prejudical influence upon the organism itself. On the other
hand, the bacterium, when growing in a sealed tube with
limited supply of oxygen, has its development brought to a
stand by the exhaustion of that gas, while the organism is
1 See ‘Comptes Rendus,’ 26th Oct., 1880.
342 PROFESSOR JOSEPH LISTER.
in full vigour and in a fluid but slightly changed from its
original wholesome condition. It thus remains like a vigorous
seed, ready to start into energetic growth when the con-
ditions for its germination are supplied.! The essential
difference between the two views may be stated shortly
thus: M. Pasteur regards oxygen as a slow poison of the
bacterium ; Dr. Greenfield seeks for the slow poison in the
products of the fermentative agency of the organism.
The time which has passed since the delivery of this
address, has brought out facts which have led M. Toussaint
to take a different view of the nature of the liquid used in
his “ vaccinations ” against anthrax above referred to. In
a letter which he had the kindness to write to me on the
subject, he informs me that on two different occasions in-
jections of anthrax blood treated by one of his methods has
led to the death of the animal from anthrax; and in one
instance, a similar injection induced a local affection which
appeared to have the characters of malignant pustule. He
has hence been led to the conclusion that the diseased
blood treated by his methods, instead of being (as he at
first believed) free from the living bacillus, contained the
organism in an “attenuated ” form.
Thus it would appear that the observations of Pasteur,
Toussaint, and Greenfield, agree in ascribing the “ vacci-
nating” influence to a modified form of the disease
concerned. .
At the same time some other observations have been made
which tend to justify the original line of inquiry pursued
by Toussaint. Chauveau has found thatif ewes inoculated
with anthrax in the last months of gestation recover from
the disease, not only are the mothers no longer susceptible,
but the lambs enjoy similar immunity.? Further, it has
been ascertained by others, including Dr. Greenfield, that
the blood and tissues of the foetus of an animal dying of
anthrax contain no bacilli, while those of the mother swarm
with them. Putting these two observations together we are
led to the inference that while the integrity of the placental
vessels prevents the bacilli from entering the fcetal circula-
tion, the foetus is so dosed with soluble products of the
development of the bacilli in the maternal blood as to be
rendered proof against the disease.
1 See “The Brown Lectures,” by W. S. Greenfield, &c.; Lecture II,
‘The Lancet,’ Jan. Ist, 1881.
2 See Dr. Greenfield’s lst “Brown Lecture,” ‘The Lancet, 18th
Dec., 1880.
APPENDAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS. 3409
Oxsservations and Reriections on the ApPENDAGES and on
the Nervous System of Arus caNncrirorMis. By E.
Ray Lanxester, M.A., F.R.S., Jodrell Professor of
Zoology in University College, London. (With
Plate XX.)
APUS CANCRIFORMIs is in many respects one of the most
important of the Crustacea. Not only is it of exceptionally
large size for one of the Entomostraca, and therefore suited
to anatomical investigation, but it possesses peculiarities of
organisation which mark it out (together with its immediate
congeners, the Phyllopoda) as an archaic form, probably
standing nearer to the extinct ancestors of the Crustacea
than any other living members of the group.
The almost world-wide distribution of the genus Apus
(Greenland, Tasmania, New Zealand, Australia, Europe,
North America, West Indies, Affghanistan, China), and its
fresh-water habit, tend to confirm the conclusion as to its
high antiquity.
But it is not only for such reasons that Apus has claims
on our special attention. Its great abundance in certain
localities renders it especially suitable for study as a type
or standard of the organisation of the lower Crustacea, and
it is on this account especially to be desired that an accurate
account of its structure should be accessible. Strange as it
appears, it is yet the fact that such an account does not
exist, and that recent writers of authority have given diver-
gent and erroneous accounts of such prominent features in
the structure of Apus as the antenne, jaws, and thoracic
appendages.
In 1841 E. G. Zaddach published a memoir entitled ‘ De
Apodis cancriformis anatome et historia evolutionis,’ which
is a most carefully worked out and admirably illustrated
monograph, worthy to be placed alongside the similar studies
of Arthropod anatomy, which were produced at about the
same period by George Newport.
Zaddach’s most valuable observations refer to the internal
anatomy and to the development of Apus from the egg, but
the problems relative to the morphology of the appendages
and the reciprocal relationships of the great groups of Ar-
thropoda which now occupy attention had not in 1841 come
into prominence, and accordingly we do not find his observa-
tions upon the various appendages altogether equal in value
to the rest of his work.
Since the date of Zaddach’s monograph the only writers
344 PROFESSOR E. RAY LANKESTER,
whom it is necessary to cite who have dealt with the struc-
ture of Apus are: Grube (*‘ Bemerkungen iiber die Phyllo-
poden’’), in the ‘Archiv f. Naturg., 1853; Baird, in his
‘ British Entomostraca,’ Ray Soc., 1850; Claus, in a paper
published in the ‘Gottingen Abhandlungen,’ vol. xvii,
1873, entitled “Zur Kentniss des Baues und der Entwick-
lung von Branchipus stagnalis und Apus cancriformis ;”
Huxley, in his ‘ Anatomy of Invertebrate Animals,’ 1877,
p- 281; Gerstaecker, in Bronn’s ‘ Classen und Ordnungen
des Thierreichs,’ “ Crustacea,” p. 860, &c., plates xxx, xxxil,
1879; and again, Claus, in the last edition (now in course
of publication) of his ‘Handbuch der Zoologie,’ p. 527,
1880.
Having made a careful examination of the appendages
of Apus cancriformis, of which I have received numerous
specimens from the neighbourhood of Munich, from Prag,
and from Padua, through the kindness of Professor von
Siebold, of Professor Fricz, and of Professor Pavesi, respec-
tively, as also of a specimen of Apus Dukii from Affghanistan,
which I owe to the kindness of Surgeon-Major Day,’ I was
surprised to find that neither Zaddach nor any one of the
authors above cited gives a full account of these structures.
Moreover, I found my results to be at variance on one or
more important points with the statements of each of my
predecessors, who also differ from one another as to the in-
terpretation of some portions of the series of limbs.
The most complete set of figures is that given by Professor
Gerstaecker of the appendages of Apus productus, which are
incorporated with reproductions of the figures of Zaddach,
Claus, and Brauer,? in the plates of his valuable treatise
on “ Crustacea’ (Bronn’s ‘ Thierreich’).
These original drawings, and the interpretation put upon
them in the explanation to the plate, appear to me to be so
inaccurate that I think that my sketches, reproduced in the
plate (Plate XX) accompanying this paper, and the following
observations, may be found of value as a contribution
towards a true history of the “‘ Krebsartige Kieferfuss” of
Schaeffer.
DeEscRIPTION OF THE APPENDAGES.
The modified limbs or lateral appendages of Apus may be
divided into four series, according to their position, viz.—l.
1 This form, recently described by Mr. Day, is perhaps the 4. Himalayanus
cited in Gerstaecker’s list.
3 *Sitzungsber. der Akad.,’ Wien, Bd. lxix.
APPENDAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS, 545
Two pairs in front of the mouth—* przoral appendages.” 2.
Three pairs of jaw-legs, more especially related to the pur-
poses of the mouth as jaws, and immediately following it—
“oral appendages.” 38. Eleven pairs of variously modified
but essentially locomotor legs, placed one on each of the eleven
body segments, in front of and inclusive of the segment car-
rying the genital apertures—“‘ thoracic appendages.” 4.
Kifty-two pairs of locomotor legs, gradually diminishing in
size, and posterior to the genital apertures (less numerous in
incompletely-grown specimens)—‘“‘ abdominal appendages.”
They are more numerous than the annulations of the integu-
ment of this region of the body, which are only seventeen in
number, but they correspond in number with the ganglionic
enlargements of the nerve cord.! There are four annulations
of the body posterior to these appendages, and devoid of a
continuation of the nervous axis, as well as of appendages.
A fifth post-pedal segment is perforated by the anus, and
carries a pair of jointed setose appendages, which may or
may not be equivalents of the legs of the anterior region.
The two pairs of appendages in front of the mouth—Both
these pairs of appendages are of small size—relatively very
much. smaller than they are in the newly-hatched larva.
The second pair is much smaller than the first, although
in the larva the reverse relation obtains. Moreover, the
second pair, like the first, are simple filamentous tactile
organs; although in the larva they are powerful biramose
swimming legs. In the adult Apus, therefore, not only with
reference to their homology with the corresponding appen-
dages of the lobster, but alsoin view of their function, these
two pairs of appendages are entitled to the names anten-
nules (1st) and antennz (2nd) respectively.
It appears to be desirable, in order to arrive at true con-
clusions with regard to the homologies of the limbs of the
Arthropoda, to abandon altogether the use of such terms as
“antenna,” “ mandible,” and “‘ maxillipede,”’ as homological
categories, and to apply them merely as descriptive terms
proper to the particular case under examination. In the
consideration of homologies the appendages should be re-
garded simply as first, second, third, and so forth, without
the introduction of terms calculated by their reference to
function to prejudice the argument as to homology. The
first appendage of an Arthropod A. may be homologous
with (or homogenous with) the first appendage or with the
’ The first four post-genital body-rings carry five pairs of legs, the next
four carry ten pairs of legs, the next four thirteen, the last five leg-bearing
hody-rings carry twenty four, as nearly as can be estimated.
VOL, XXI,——NEW SER. | z
346 PROFESSOR E. RAY LANKESTER.
second or third of another Arthropod B., and so on; but
ambiguity is inevitably introduced if we attempt to indicate
this homology by the use of such terms as antennule and
antenna, to be applied in both cases alike, for in such cases
as the parasitic Copepoda, the various Arachnida, and the
living and fossil branchiate scorpions (Merostomata), these
descriptive terms, and others like them, are found to be
absolutely contrary to fact in their implications, and in-
volve also debatable assumptions in reference to ancestral
primitive forms.
The first pair of appendages of Apus cancriformis may,
therefore, be described as functional antenne. Hach con-
sists of two segments, separated by a joint or soft ring of
the chitinous cuticle, which allows the bending of one joint
upon the other ; but there does not appear to be any muscular
band entering the appendage in the adult Apus. A variable
number (two to four) of sets’ are set upon the free end of
the appendage.
The second pair of appendages is alsoantenniform. Hach
consists of a single filament, the base of which is attached
to the under surface of the head, not far from the first.
The filament is strongly curved but possesses no joint,” nor
does any muscular fibre penetrate its axis. It tapers
towards its free extremity which is setiform. Its total
length is about one third of that of the first pair.
In the adult Apus cancriformis and in Apus Duki, from
Affghanistan (? 4. Himalayanus), this second pair of preoral
appendages, although reduced to a rudimentary condition, is
always present, so far as my observations go. I have found
them always present in full-grown specimens of Apus can-
criformis from Munich, from Prag, and from Padua.
Their existence in the adult has recently been denied.
Zaddach states that they are generally absent in A. cancri-
formis, but were found by him in two cases; Huxley states
that he was unable to find them in Apus glacialis examined
' The sete of Crustacea are in distinction from the bristles of Chetopods,
which are also often called “sete,” superficial prolongations of the con-
tinuous chitinous cuticle which is produced by the epidermis, and are not,
as are the bristles of Chetopoda, formed in open or closed follicles each as
the cuticular excrescence of one specialised cell of the epiderm. It wouid
be well to distinguish the follicle-formed sete of Chatopoda as ‘ chete ”
or ‘‘ cheetomes.”
? A comparison with Zaddach’s and Claus’s figures of Apus larve leads to
the conclusion that the part of the larval second antenna which thus sur-
vives is the base and short prowimal ramus (neither exopodite nor endo-
podite); all beyond this forming the larger part of the larval antenna
ppears to atrophy completely.
a
APPENDAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS, 347
by him, whilst Claus, whose statements have the very
greatest weight, both on account of his extended investi-
gation of the morphology of the Crustacea and of his special
observations on the development of Apus and Branchipus,
brings forward the total absence of the second pair of
preoral appendages in Apus as a special characteristic of
the family Apuside. He says, in the fourth edition of his
‘ Grundziige der Zoologie,’ 1880, p. 527, ‘* Die Tastantennen
sind kurz zweigliedrige Fadchen, die hintern, welche bei der
Larve einen zweiastigen Ruderarm bilden, fallen ganz aus.”
A similar statement occurs on p. 523. Gerstaecker offers
no original observation on the subject, nor does he figure
either the first or second pair of appendages of the Apus
productus, which he has illustrated in his Pl. xxx, but con-
fines himself to quoting the statement of Zaddach.
The complete suppression of a pair of appendages is a
matter of some importance, and in this particular case the
presence or absence of the pair in question has a special
interest in relation to the condition of that part of the
nervous system by which they should be supplied. The fact
is that, though rudimentary, the second pair of preoral
appendages (so-called antenne) is present in the adult Apus
of at least two species.
Abdominal appendages: appendages behind the generative
apertures.—It will be most convenient to pass next to the
description of this group of appendages, since they appear to
present the least specialised form of the whole series.
It has been customary to regard the higher Podophthal-
mata as a standard for the morphology of Crustacean
appendages, and to interpret the parts seen in other Crus-
tacea by reference to them, and to apply to those parts the
analysis indicated in the terms protopodite (including coxo-
podite and basipodite), endopodite, exopodite, and epipodite.
When, however, the question is looked at from the point of
view of evolutional morphology, there appears to be no
ground for expecting that the analysis applicable to the
special adaptations of the Podophthalmata should also be
applicable to the lower Crustacea, and it will be best to
consider the parts of the appendages of Apus merely in
reference to one another and to the appendages of closely
allied forms, deferring for the present the consideration of
the homologies or agreements of these parts with those of
widely separated forms.
Taking the first post-genital appendage of the right side
(seventeenth of the whole series), we find it to be a leaf-like
plate attached by one end to the body, so that its flat sur-
ie)
348 PROFESSOR E, RAY LANKESTER,
faee is vertical to the ventral surface of the animal, and at
right angles to the antero-posterior axis. It is provided
with numerous lamelliform processes. The median portion
may be spoken of as the axis or corm, whilst the processes
may be called “ phyllites” or “apophyses,” those ranged
along the ventral or neural border of the corm being called
“ endites,”’ and those given off from the dorsal border being
called “ exites.” There are six endites, and two exites much
larger than any of the endites, whilst in front of (distal to)
the two large exites is a less strongly marked outgrowth of
the corm, which it will be convenient to call the “ sub-apical
lobe.” The corm is devoid of segmentation or jointing,’ its
chitinous cuticle forming one continuous investment to it;
and moreover, no muscles are inserted into the corm in such
a way as to cause it to bend upon itself, and so call into
existence functional, if not structural joints.*
The cuticle is thin at the base of the corm, where it
becomes continuous with that of the ventral surface of the
body, and the movement upon the joint so constituted is
provided for by powerful muscles, which enter the appendage
and are inserted into its walls.
Of the six endites the proximal is somewhat isolated and
pushed towards the middle line. Its surface is beset with
powerful sete, and it clearly has the function of assisting,
by means of apposition to its fellow of the opposite side, in
seizing and moving particles which may be introduced into
the mouth. It is a jaw process, and may be spoken of as
the “‘ gnathobase,”’ It is a fact of no little significance that
a gnathobase is developed on every one of the sixty-three
postoral appendages of Apus, especially when we remember
that a similar feature is characteristic of Limulus, the most
archaic representative of the Arachnida.
The gnathobase of the appendage under consideration is
provided (as is the rule throughout the whole series) with
powerful special muscles inserted into the corm (see figure),
but it is not possible to define any arthrodial thinning of
the cuticle which marks it off from the corm as a distinct
segment.
1 Zaddach describes the corm as three-jointed, and Huxley states that
in Apus glacialus it consists of coxopodite, basipodite, and ischiopodite. I
cannot find any evidence of these joints in the specimens studied by me
in any of the appendages excepting the first two of the thoracic series.
2 Such functional joints not indicated by any thinning of the chitinous
cuticle to form an arthrodial membrane appear to exist at the bases of manv
of the phyllites in limbs from various parts of the body, and are indicated
by the insertions of the muscles in the appendages of various erustacean
Nauplil, as well as in those of the remarkable Rotifer, Pedalion. oe
APPENDAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS, 349
On account of its possessing muscles capable of moving it
upon the corm, the gnathobase may be distinguished from
such outgrowths of the corm as are devoid of muscles or not
jointed at their base. Such outgrowths or apophyses pro-
bably are phylogenetically antecedent to outgrowths capable
of flexion, or actually jointed at their base ; accordingly, the
simpler early condition may be indicated by the term “lobe,”
whilst the later flexible condition is indicated by the term
“* arthrite.”
Mere lobes tend in various regions of the arthropod body
to become arthrites, e.g. the spines on the abdominal cara-
pace of Limulus, or, again, the carapace of some Entomo-
straca and the wings of insects.
Further, an arthrite may be monarthrous, or, as we shall
see exemplified in other appendages of Apus, may become
polyarthrous.
The four endites distal to the gnathobase are oval, leaf-
like bodies, of which the proximal is somewhat broader than
the others, and is, by exception in this and other appendages
of the post-genital region, devoid of a special muscular slip,
and therefore in the condition of a lobe instead of an arthrite.
The three apophyses distal to it (3, 4, 5) are true arthrites,
each being connected at its base with a muscular slip, which
unites with its fellows to form a powerful muscle traversing
the corm and inserted into the body wall. The arrangement
of setze on these endites is characteristic, and is best under-
stood by reference to the figures.
The distal endite (6) is much larger than the preceding,
and is attached at the point, which is practically the apex of
the corm. It spreads both ventrally and dorsally from its
point of attachment, so that a dorsal process may be distin-
guished from a ventral. It is provided with a muscle dis-
tinct from that of the other endites which traverses the
corm.
Next in order we come to the sub-apical lobe, which may
be regarded either as the termination of the axis of the
corm or as the distal lobe of its external or dorsal border.
In the appendage under description (the first post-genital),
the subapical lobe is exceptionally large, but it is here as
always a lobe-—devoid of muscular supply, and not in any
way jointed.
Passing midward along the dorsal border of the limb, we
come to the largest of all the outgrowths of the corm—the
pee exite (counting the proximal as the first) the flabellum
or fan.
It has been usual with authors to speak of this exite as a
850 PROFESSOR E. RAY LANKESTER,
branchia, and to distinguish it from the next exite as the
“lamelliform branchia,” whilst the latter is termed the
“bottle-shaped branchia.”” But the fact is, that it is
possible with justice to attribute a respiratory function to
any such broad lamelliform structure, although it may
have other important functions. The flabellum is moved
by three muscular slips arising from the corm, and is first
of all a swimming or fanning plate. It is more highly
developed as an “arthrite” than any other of the out-
growths of the corm. It is somewhat triangular in shape,
attached by one angle to the corm, and has a setose
margin.
The proximal or first exite is not really vesicular although
frequently described as being so. It is somewhat thicker
than the flabellum—oval in shape, with a very narrow and
short pedicle, by which it is connected with the corm. It is
devoid of seta, and not provided with any muscles. It must
be regarded as a “ lobe ” (in the sense above defined) rather
than as an “arthrite.” Throughout the series of limbs where
present this proximal exite has much the same shape, it is
always without sete and is invariably devoid of muscular
connections, although strongly emarginated and attached by
but a slender neck to the corm. It can therefore have no
locomotor function, and is, in virtue of negative qualities, the
branchial outgrowth. On account of its passive character,
as contrasted with the active fanning flabellum, it may be
called the dract (bractea—a weather-cock).
In form the abdominal appendages which follow the first
post-genital pair agree closely with the latter in all respects,
except in the reduction of the relative size of the subapical
lobe.
In size they undergo a gradual and very great reduction,
so that the proportionate size of the last of the series is
represented by the small fig. 13, of Pl. XX. The whole
appendage is little bigger than the gnathobase of the first
post-genital limb.
Gerstaecker’s figure of the thirtieth truncal appendage in
Apus productus (his Pl. xxx, fig. 10) appears to me to be
inaccurate. These minute processes are easily mutilated in
removing them from the body, and such has probably been
the case with the appendage figured by him. The “ flabel-
lum” appears to have been broken away in Gerstaecker’s
specimen, and what he marks as flabellum (d7.) is in reality
the subapical lobe.
Abnormal appendage-—Any abnormality ina Crustacean
appendage is of interest, as showing possible directions of
APPEN DAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS, 351
new development or recurrence of ancestral conditions of
form. In Pl. XX, fig. 12, an abnormal specimen of the
fortieth appendage, right side, is drawn. The abnormality
consists in the development of a second flabellum nearer the
base of the corm than the first, and this is accompanied by
an almost complete reduction of the bract. The additional
flabellum is much smaller than the normal one, but has a
similar form, and is supplied with a muscular slip.
Thoracic appendages, or appendages at and in front of the
genital apertures and behind the specialised oral appendages.
—It will be most convenient to examine these appendages
by proceeding from behind forwards.
Oostegopods.—The pair which are attached to the segment
in which the genital ducts open in female specimens of Apus
are, as is well known, modified so as to form receptacles for
the eggs. Inthe males, as shown by Brauer (‘ Wiener Sitz-
ungsber,’ vol. lxix), the appendages of this segment are in
nowise different from those of the segments immediately in
front of them.
The oostegopods, or brooding-legs (as the eleventh pair of
the thoracic appendages may be called), present the following
peculiarities as compared with the appendages in the region
posterior to them. The gnathobase and four succeeding
endites are normal (Pl. XX, fig. 10), and resemble those of
the next posterior appendage (PI. XX, fig. 11), but the sixth
endite is greatly modified. It is expanded and confluent with
the subapical lobe (p). The subapical lobe is widely pro-
duced in the form of a hemispherical cup. On to this ex-
pansion the flabellum (F/) fits as a lid—an emarginated
aperture being formed posteriorly to its short peduncle by
the notching of its border (Pl. XX, fig. 10, ov).
The great development of the subapical lobe and modi-
fication of the flabellum seems to have entailed an atrophy
of the bract (Br), which exists in a rudimentary filamentous
condition (compare the abnormal appendage drawn in
fig. 12).
The general form of this appendage has been described by
many previous observers, and the relations of its parts to
those of neighbouring appendages correctly pointed out. The
correspondence of the immovable, cup-like portion, developed
from the axis or corm, with the conjoined sixth endite and
subapical lobe (which is relatively large in the next following
appendage posterior to it, fig. 11), has not, however, been
insisted upon. Zaddach correctly identifies the movable lid
with the flabellum, and figures the limb in an immature con-
dition with the rudimentary bract present. He states that
352 PROFESSOR E, RAY LANKESTER.
usually the rudimentary bract is absent in the full-grown
condition, but I have, on the contrary, never failed to find
it. Claus (loc. cit.) likewise figures this appendage from a
larval Apus, and correctly identifies its component parts and
the rudimentary bract which does not enter into the compo-
sition of the egg box. Huxley also (loc. cit.) describes the
adult oostegopod, but without mentioning the rudimentary
bract ; he, however, identifies the movable lid as the flabellum
(his “‘ exopodite’’), and the fixed cup-like portion as an out-
growth of the axis (his ‘‘ endopodite”). Gerstaecker, how-
ever, having missed the rudimentary bract (which may or
may not be present in the Apus productus figured by him),
proceeds to identify the fixed portion of the egg box with the
flabellum (his “lamelliform branchia”), and the movable
lid with the bract (his vesicular (blasenformiger) branchia).
Gerstaecker’s being the latest study and identification of
these organs, it is of some importance to point out emphati-
cally that the movable lid is not the bract, but the flabellum,
whilst the bract exists in Apus cancriformis in a rudimentary
condition in the adult appendage, as exhibited in Pl. XX,
fig. 10.
I have not had an opportunity of examining, in the living
state, the exact disposition of the muscles and the mechanism
of the egg box, but I must point out that the cireular
muscles described by Zaddach have no existence. The
modified flabellum alone has a muscular supply, which does
not differ from that of the other flabella.
Appendages next in front of the oostegopods.—A marked
difference in the proportions of the outgrowths of the limbs
in front of the oostegopods is observed, as compared with
those posterior to those specialised appendages.
In Pl. XX, fig. 9, the ninth of the thoracic (pregenital)
series of foot-like appendages is represented. Whilst the
gnathobase (endite 1) and the four next endites (2, 3, 4, 5)
present no peculiarity for notice, the sixth endite is remark-
able for its firmly chitinised walls, its denticulate ventral
margin and its ex-axial lobe, which projects beyond the point
at which the endite is articulated to the axis, and works in
a notch of that portion of the limb.
The subapical lobe (p) is well developed and acutely an-
gular. The flabellum is more elongated than in the
abdominal (post-genital) appendages, being developed on
either side of its point of attachment to the axis, instead of
being quadrate or oblong. The two regions of the flabellum
may conveniently be spoken of as “the distal lobe’ (that
apexwards in relation to the muscular attachment), and
APPENDAGES AND NERVOUS SYSTEM OF APUS CANCRIFORMIS, 353
‘the proximal lobe” (that basewards, in relation to the same
attachment).
It is important to note this development, since in some
Phyllopods and other Crustacea it is very greatly exagge-
rated, and the flabellum practically divided into two moieties
(see woodcut, fig. 1, XIX, XIV, and VI, Fd).
The muscles distributed to the endites and the flabellum
are more strongly developed in the pre-genital than in the
post-genital appendages of the locomotor series, as may be
seen by comparing Pl. XX, fig. 9, with fig. 11. Whilst in
the post-genital appendages endite 2 ceases to have a distinct
muscular slip supplied to it, this endite, like all the others,
has in the pregenital series a muscular slip from the great
muscle of the axis, which is distributed to the five distal
endites. The sixth endite has, in addition, a separate
muscle, which runs parallel with the common muscle of the
endites, and the first endite or gnathobase has also its own
special muscles. The muscular supply of the sixth and first
endites is the same in all the thoracic aud abdominal appen-
dages, excepting the first two of the thoracic series (two
anterior thoracic feet of authors).
The bract is in all cases devoid of any muscular supply—
a fact which is not without importance in the determination
of its homologue in other Crustacea.
The appendages in front of the ninth of the thoracic
series have a form closely similar to that drawn in Pl. XX,
fig. 9, the endites becoming slightly more elongated in form,
and the axis also elongated, so as to separate the endites
from one another in those nearest the first two thoracic
feet.
The first two thoracic feet require special description.
Second thoracic foot.—This appendage is drawn in Pl. XX,
fig. 8. The most important feature which it presents, as dis-
tinguished from those behind it which have been already
considered, is the jointing of the corm or axis. The corm
is divided into two segments or pieces by a soft fold of its
chitinous cuticle, and muscles are attached to the distal
segment so as to move it upon the basal segment. To the
basal segment (Az!) are attached the two proximal endites
(en! and en*), whilst the four distal endites, the flabellum and
the bract, are attached to the distal segment (Adz). The
endites are much elongated and notched at their margins,
retaining, however, a flat or lamelliform character. The
terminal endite (en®) is strongly denticulate and has its ex-
axial process markedly developed, whilst the notch in the
axis into which this process fits is peculiarly constructed, as
354 PROFESSOR E, RAY LANKESTER.
may be best understood from the figure (Pl. XX, fig. 8, p 2),
and from the similar structure more definitely developed in
the thoracic appendage (fig. 7 a.). I am not able to suggest
what may be the significance of this lobe and notch, which
has not been hitherto noticed by those who have described
Apus, but it in some degree suggests a comparison with the
peculiarly modified lobes on the first thoracic foot of the
male Limnetis brachyurus (as described by Grube, Wieg-
mann’s ‘ Archiv,’ 1853).
The sub-apical lobe is relatively small, the flabellum and
bract similar to those of hinder appendages.
First thoracic foot.—This appendage is more strikingly
modified than any one of the locomotor series, excepting the
oostegopods, the remarkable feature being the elongation
and jointing of the four middle endites in the form of fila-
mentous flagella. The axis or corm of this appendage is
divided into four successive segments, which are marked in
the figure respectively Aw, Ax, Axv®, Ax* (Pl. XX, fig. 7).
These segments are movable upon one another, the chitinous
cuticle being soft so as to form an “arthrodial membrane ”
between the successive joints. This is the only one of the
truncal series of appendages (those following the oral appen-
dages) which presents four joints to the corm, whilst the
second thoracic foot is the only other appendage of the
truncal series which presents a joint in the corm at all and
in it only two segments exist. The literature on the development of the spermatozoa is
very copious, more particularly that which treats of the
development in Mammals, as may be seen by reference to
the papers of von la Valette St. George in the ‘ Archiv fir
Mikr. Anatomie.’
I do not propose to consider every individual publication,
but to mention those who have put forward plans of sperma-
togenesis capable of application to the whole, or at any rate
large, divisions of the animal kingdom; but before doing
this I may briefly state what my own views on the sub-
ject are.
A cell whose future destiny is male (spermatospore) com-
mences to undergo changes which fit it for its new function,
and by a process of multiplication gives rise to many ferti-
lising elements. The first steps are division and multipli-
cation of the nucleus, and a corresponding constriction of the
surrounding plasma, till a multicellular mulberry-like mass
(sperm-polyplast) is produced, which may be solid or hollow,
consisting of young spermatozoa or spermatoblasts. During
this process some portion or portions of the original cell
cease to undergo further change and remain behind to
support and nourish the developing spermatozoa (blasto-
phoral cell). t
The nucleus of the spermatoblast forms the head of the
spermatozoon, and the tail is formed by the centripetal or
centrifugal elongation of the plasma. When fully formed
the spermatozoa are supported on the blastophoral cells till
required and then shed off, leaving their supports to atrophy
and decay.
How far this view holds good for the Mammalia I am not
able to say precisely, but the abundance of figures confirm-
ing the above account in papers treating on this subject,
justifies the idea (compare the account below of Meyer’s
paper) that spermatogenesis will be found to be essentially
the same in that class.
Many of the figures show the blastophoral cell under
various names, and represent stages which seem in most
THE DEVELOPMENT OF THE SPERMATOZOA. 425
respects comparable to those found in the spermatogenesis
of Helix.
Kolliker (‘Zeit. fiir Wissen. Zool.,’ Bd. vii, p. 201) seems
to have been the first to give a plan of spermatogenesis.
He gives figures of developmental stages from the bull,
pigeon, frog, and carp; at the same time noting that the
account holds good for all animals.
He believed that the spermatozoa were developed by a
direct metamorphosis of the nuclei of the cells of the testis.
This change takes place in what he calls “ Blaschen,” which
are probably nothing more, as Meyer suggests, than poly-
plasts modified by the fluid (Miller’s) with which he
treated them. THe conceived that the tail as well as the
body originated from the nucleus.
He very shortly describes the process in the frog, but with
the exception of the figures, which show well the bundles of
spermatozoa united by the blastophoral cells, there is little
agreement between my account and his.
V. la Valette St. George has, in his fifth communication,
“On the Development of the Spermatozoa,” to Max Schultze’s
‘Archiv, Bd. xv, p. 261, given an account of sperma-
togenesis in general.
The paper commences with an exhaustive résumé of
previous observations and papers published in connection
with the subject, and then gives an account of the process
as he has observed it in many Mammalia—bull, ram, stallion,
rabbit, &c., and ends with a summary which embodies his
ideas of spermatogenesis based on his former papers. He
recognises in the testis tubule two kinds of cells. Of the
first, he says, ‘* Peculiarly like young ovarian cells they are
destined to multiply as Ursamenzellen or Spermatogonia ;
in a similar manner by division and by transformation of their
descendants (the Spermatocytes) they are destined to give
rise to the’spermatosomes (Samenkorperchen). They pro-
duce a mass of cells which either by an arrangement of the
peripheral cells develop a special cover—Keimkugeln, Sa-
menkugeln, Spermatocysten (Insects and Amphibia), or
remains coverless—Samenknospen, Samensprossen, Sperma-
togemmee, whilst the protoplasm which belongs to each cell
is more or less segmented. In many cases one of the cells
resulting from the division or its nucleus is preserved at the
foot of the Spermatogemme.”
“The second kind of cell which I call follicle cells are
bound together into a tissue which, while it embeds the
Spermatogonia, also covers and protects the Speratom-
gemme in their multiplication by division.”
426 J. E, BLOMFIELD.
From this it will be seen that he recognises the cell which
is formed at the base of the Spermatogemme as being part
of the original cell which has been left behindin the growth
and multiplication of the others, but he does not appear to
recognise the similarity between this cell and those which
are found in the Spermatogemme or Samenkugeln of the
frog which is formed in the same way, and has a similar
function.
In Semper’s “ Monograph on the Urogenital System in
Elasmobranchs” (‘Semper’s Arbeiten,’ Bd. ii), he gives an
account of the development of the spermatozoa. The section
of a mature ampulla, with its bundles of spermatozoa, is
very like that of the frog; each bundle is connected with a
nucleated mass which rests on the wall of the ampulla, and
which he calls, from its protective function, ‘ Deckzelle,”
though he recognises it as being the remains of the Mut-
terzelle. He traces the fate of these bodies after the sperma-
tozoa are shed, and finds that they undergo fatty degenera-
tion, the nuclei fall together and are only held together by
a granular detritus, while the ampulla itself collapses. This
he compares to the formation of the corpus luteum in the
ovary. In Elasmobranchs there is a continuous development
of spermatozoa in the testis from within out, so that we get
degenerated ampulle, full ampulle, ampulle with sperma-
tozoa developing, and the formation of ampulle in the same
testis, not coming as in Rana in successive crops from the
same ampulla. The spermatozoa do not develop as in Rana
from vesicles (hollow polyplasts), but on a plan more like
that of the snail. He calls the young immature sperma-
tozoa spermatoblasts, and says that he was unable to make
out the origin of the tail.
Klein, in his ‘Atlas of Histology,’ gives an account of
spermatogenesis based on researches on man, rabbit, mouse,
&c. In the contents of the seminal tubules he recognises
two kinds of cells, the inner and outer seminal cells. The
latter present two kinds according to the state of the
nucleus; in one kind the nucleus is finely granular, in the
other it is devoid of a limiting membrane, and has rods or
filaments twisted in many directions in its interior.
Nearer the lumen of the tubule are the inner seminal
cells, which are seldom limited to one or two layers. They
do not directly touch each other, but are joined by an
‘interstitial substance. These cells are polyhedral from
mutual compression, and their nuclei are similar to the
second type of the outer seminal cells, that is, they contain
rods or filaments variously arranged. Their nuclear rods
THE DEVELOPMENT OF THE SPERMATOZOA. 4.27
vary in shape and arrangement, which he considers indica-
tive of division and multiplication. Nearer still to the
lumen of the tube the cells are loosely connected, and they
may be seen dividing each into two daughter nuclei. These
small cells, the daughter cells, undergo changes leading to
the formation of the spermatozoa, and for these he uses
Sertoli’s term spermatoblasts. The first change is seen in
the nucleus, which becomes finely granular and assumes a
membrane. This kind of nucleus he calls the resting
nucleus. At the same time it moves to one pole of the
cell, which is itself elongated, and constitutes a “ granular
mass,” separated from the nucleus by a “ clear bag.” When
the young spermatozoa are in this state they assume a defi-
nite arrangement, and become placed in fan-shaped groups
along the tubule, with the handle of the fan sunk among
the seminal cells; their further progress consists in elonga-
tion. He then goes on to mention the views of Ebner and
Neumann, who consider that the groups of spermatozoa are
formed in a single cell which consists of a base, which has
(Ebner) or has not (Neumann) a nucleus next the membrana
propria, a peduncle, and a broad mass at the end of the
peduncle in which the spermatozoa are produced.
He regards the head, as well as the “ middle piece,” as
formed from the nucleus.
In Rollett’s ‘ Untersuchungen aus dem Institut fur Phys.
und Hist.’ for 1871, there is a paper by v. Ebner, in which
he gives an account of the development of the spermatozoa
in the rat and mouse, referring to other mammals, and a
series of drawings illustrating that process in the first-named
animal.
He divides the processes into eight stages, which I will
not enumerate, but try to epitomize his account. The funda-
mental idea in which he differs from other writers is in the
existence of a “ Keimnetz,” in which the spermatozoa are
developed. This consists of a welded mass of cells next the
tunica propria of the tubule in which two kinds of nuclei are
discerned, the one pale, nucleolated, with distinct outline; the
other granular, dark, with anindistinct outline. On taking a
* superficial view of this layer it has the appearance of a net-
work. From it processes project towards the lumen of the tu-
bule which, when first formed, are nothing but plasma; then
nuclear hardenings commence at its inner extremity, which
soon unmistakably assume the appearance of spermatozoa
heads, in this case being pointed at one end, which end is
directed towards the periphery. The tails are formed from
the plasma. At the base of this process, which he calls a
VOL, XXI.—NEW SER, F F
428 J. E. BLOMFIELD.
spermatoblast, there is often a nucleus, which can be distin-
guished by its slightly irregular shape, and from its being
elongated in the direction of the spermatoblast, but he gives
no account of the origin or fate of this nucleus.
The spaces between the processes of the “ Keimnetz” are
filled up with cells of various sizes and in various states of
multiplication. These he regards not as in any way con-
cerned with the formation of the spermatozoa, but only
present to assist the growth by supply of nutritive material
to the young spermatozoa ; and he traces their origin to their
having wandered from the lymph spaces of the testis. As
regards their fate, he believes that they form the coagulated
particles, or ‘‘ Kiweisskugeln,” which are to be found in the
lumen of the tubule of a ripe testis. Sometimes these bodies
contain crumpled-up semilunar nuclei.
It is obvious from this that part of the ‘‘ Keimnetz”’ cor-
responds to my testicular epithelium, the outer seminal cells
of Klein, and the “ Ursamenzellen ” of other writers ; more-
over, the two kinds of cells which Klein mentions as being
in an active or passive condition, according to the condition
of the nucleus, are here clearly indicated.
As regards his spermatoblast, he says that, as far as his
observations went, it arose without any division of a nucleus,
but in this I believe he will be found to be mistaken. And
it is my opinion that the nucleus at the base, and the nuclei,
as he says, newly formed at the other end, are due to a
division of one cell...
As regards the cells which lie in the meshes of the net-
work, and which, he thinks, are only of use for the nourish-
ment of the spermatozoa, the opinion of almost every other
writer is that they are concerned in the formation of the
spermatozoa and represent various stages of the process.
These are the inner seminal cells of Kiein, the Spermato-
gemme and Samenknospen of v. la Valette St. George, and
the idea that they form the “ Eiweisskugeln,” and similar
bodies found in the lumina of the tubules, is untenable.
I think these bodies will be found to owe their origin to
the breaking up of blastophoral cells which, as in the frog,
after the spermatozoa are ripe and have dropped from their
supports, themselves are thrown off and undergo fatty dege-
neration.
It may be mentioned that he considers the middle piece
to arise from the same consolidation of plasma as the
nucleus. |
In the ‘ Archiv fiir Mikr. Anatomie,’ vol. xviii, p. 233,
Prof. Flemming has a paper in continuation of his researches
THE DEVELOPMENT OF THE SPERMATOZOA. 429
on cells and nuclei, in which he gives an account of the
formation of the spermatozoa in salamander. ‘The interest-
ing point for our purposes is that which refers to the forma-
tion of the head of the spermatozoon, not, as has been sup-
posed since the observations subsequent to Koiliker’s paper
appeared, from the whole nucleus, but from that part of it
which he calls the “ chromatin.” This collects into a spirally
folded mass, which becomes more closely folded as it in-
creases in length, till the whole head may be seen coiled up
in the nucleus. The origin of the tail he traces to the cell
plasma. These observations agree with those of Kolliker if
we substitute spermatozoon head for the whole sperma-
tozoon.
I have not worked with sufficient detail to determine the
exact origin of the spermatozoon head, but I must confess
that my ideas agreed with those of previous observers that
the whole nucleus took part in the formation of this struc-
ture, though, since the publication of Flemming’s paper, I
should not like to say that it was so, and can only hope to
make some observations on its exact origin in the Mammalia.
In the earth-worm it is not possible to distinguish in the
nucleus ‘‘ chromatin” from other constituents, and hence
the head of the spermatozoon cannot be traced in this case
to such an element.
The most recent utterance on this subject is by Meyer,
in the ‘ Memoirs of the St. Petersburg Academy,’ tome xxxii,
1880, and as it contains many figures confirmatory of my
views, I purpose to give a slightly more lengthy account
of it.
His observations were made on the dog, cat, rat, mouse,
bear, rabbit, and guinea pig. In a testicular tubule next
the wall are found the Ursamenzellen, which consist of two
kinds of cells, one small, often darkly granular, which he
calls follicle cells, the other larger, with large nucleus, each
containing a nucleolus, the nucleus itself being surrounded
by a clear plasma.
These would be the outer seminal cells of Klein, or what
I have called the testicular epithelium and its interstitial
cells.
The first change which an Ursamenzelle undergoes is
division. This takes place in a tangential direction, and
the cell which is directed towards the lumen of the tube
takes on the characters of a spermatocyte, which consists in
the nucleus and plasma becoming darker and more granular
(cf. his Taf. ii, fig. 94). The spermatocytes thus formed by
division from the Ursamenzellen gradually increase in size
430 J. E. BLOMFIELD.
and assume an oval form. The next stage consists in a
multiplication of this nucleus, apparently by its breaking up
and a reappearance of the pieces in two or three places, pro-
ducing a corresponding number of nuclei. By a repetition
of this process the Spermatogemme is produced (figs. I—29,
Taf. i). These bodies he regards as fundamentally a collec-
tion of several cells, and in support of this view adduces the
fact that a single spermatocyte may run its course to a
mature spermatozoon without presenting this form, never
possessing more than one nucleus. ‘These bodies have a
radial arrangement in the testicular tubule and an elongated
shape from the pressure of the surrounding cells, but they
are generally spherical when isolated and floating free in a
liquid.
The last stage is the change of the nucleus to form the
head and the division of the plasma of the Spermatogemme
into tongue-like processes which form the tail. The first
ehange varies according to the animal examined, that is, to
the shape of the spermatozoon head. He regards the middle
piece as derived not from the nucleus, but from the plasma.
The rest of the plasma which has taken no part in the for-
mation of the spermatozoa remains behind for a time to
support them, but finally undergoes a kind of fatty degene-
ration.
He recognises the existence of v. Ebner’s spermatoblasts
under the name of “ Samenahren,” and says that “ interme-
diate forms may be seen from the spermatocyte to the mature
‘Samendhren’ connected with the Ursamenzelle, to which
they owe their origin, by a process of plasma (figs. 35, 36,
38, 40).”
He disagrees with v. la Valette St. George in thinking
that the interstitial cells do not multiply at the same time
as the Ursamenzellen, and form layers round the spermato-
cytes and Samensprossen as the last named observer does.
From this account it will appear that his Samenahren
are the bases of v. Ebner’s spermatoblasts, and correspond
to the cell which is left at the foot of the Spermatogemme
described by v. la Valette St. George.
The foregoing papers of which I have given an account
are few out of many, but they embody the results of those
which I have not mentioned, and taking into consideration
the facts and drawings given in them it seems possible to
reconcile to a large extent the different accounts of sperma-
togenesis in mammals in the following short résumé,
omitting as far as possible the particular terms used by each
author. ‘The wall of the testis is lined on the inside with a
THE DEVELOPMENT OF THE SPERMATOZOA. 431
testicular epithelium, in which the true testis cells are sup-
ported by interstitial cells. One of these testis cells divides
tangentially, giving rise to two cells which are held together
by a common plasma; the cell next the lumen of the tube
grows and the nucleus multiplies, giving rise to several (8—
12, according to v. Ebner) nuclei embedded in a plasma;
or, according to Meyer, the cell and its nucleus may pro-
ceed to form a single spermatozoon without multiplication.
These nuclei form the heads of the spermatozoa, and the
plasma the tails. When nearly mature the young sperma-
tozoa are supported on the plasma, but when they are ripe
they are cast off from it and enter the lumen of the tube.
After the spermatozoa have left it this body itself is thrown
off with its nucleus, which has remained at its base, and
undergoes fatty degeneration, being found in the lumen of
the tube in this state.
For convenience I append a list of synonyms which are
used by various authors in describing the process of sper-
matogenesis.
1. Spermatospore = Spermatogone (St. George, Meyer).
la. Spermatocyte, intermediate form (St. George).
2. Sperm-polyblast = Blischen (Kolliker), consisting of the following :
3. Spermatoblasts = Spermatoblasts of Semper, Klein, Sertoli, or Samen-
sprossen or Spermatogemme (St. George, Meyer).
4, Mature spermatozoa, united into bundles by blastophoral cells (sperma-
toblasts, v. Ebner). Samenahren (Meyer).
5. Spermblastophor = Deckzellen of Semper.
. Testicular epithelium = Ursamenzellen (St. George).
. Interstitial cells = Follikelzellen (St. George, Meyer).
No
4.32 ADAM SEDGWICK.
On the Harty Devevopment of the AntERIorn Part of the
Wotrrtan Duct and Bopvy im the CuxicK, together with
some RemarKs on the Excretory System of the VERTE-
BraTa. By Avam Sepewicx, M.A., Fellow of Trinity
College, Cambridge. With Plate XXVI.
Tue following paper is divided into two parts. The first part
contains an account of observations on the development of the
Wolffian duct and anterior Wolffian tubules in the chick, being
supplementary to my paper on the “ Kidney of the Chick.’”!
The second part is devoted to a discussion of the vertebrate
excretory system in general.
I. Early Development of the Wolffian Duct and Anterior
Wolffian Tubules in the Chick.
The first trace of the Wolffian duct is visible in an embryo
with eight protovertebre as a slight projection from the inter-
mediate cell mass towards the epiblast in the region of the 7th
and 8th protovertebre. The projection also extends back
behind the region of the protovertebre for a short distance.
In a chick with nine or ten protovertebre a similar condition
is found, z.e. a projection from the intermediate cell mass
towards the epiblast in the region of the 7th, 8th, 9th, and 10th
protovertebre, and for a short distance behind the region of
the protovertebree.
In a chick with ten protovertebre the projection is beginning
to show signs of separation from the intermediate cell mass at
certain points. The appearance presented by the rudiment of
the Wolffian duct m the 10th segment of a chick with ten seg-
ments is shown in fig. 1.
In a chick with eleven protovertebre the rudiment of the
Wolffian duct is still present as a projection from the inter-
mediate cell mass in the region of the 7th, 8th, 9th, 10th, and
11th protovertebre ; but behind the region of the protovertebrz
it has grown back for a short distance between the epiblast and
mesoblast as an irregular cord of cells not connected to the
peritoneal epithelium. A partial separation of the Wolffian
duct from the intermediate cell mass is now effected in the
region of the 7th to the 10th protovertebre. This separation
is not, however, complete; but the Wolffian duct remains connected
' «Development of the Kidney in its relation to the Wolffian Body in
the Chick,” ‘ Quart. Journ. Mic. Sci.,’ vol. xx.
WOLFFIAN DUCT AND BODY IN THE CHICK, 433
to the peritoneal epithelium at certain intervals by short cords
of cells.
In a chick with twelve protovertebre the separation of the
Wolffian duct from the intermediate cell mass in the region of the
7th to the 11th protovertebre inclusive is as complete as it ever
will be, z.e. it has separated for the greater part of its length, but
remains attached to the peritoneal epithelium at certain points,
by cords of cells (fig. 2) derived from the cells of the inter-
mediate cell mass connecting the rudiment of the Wolffian duct
with the peritoneal epithelium. ‘These cords of cells are the
commencing Wolffian tubules of the anterior part of the Wolffian
body, and are more numerous than the segments in which they
are placed. Behind the region of the protovertebre in a chick
of this age (twelve protovertebre), the Wolffian duct has grown
back as an irregular cord of cells (fig. 6), independent of the
intermediate cell mass, for a short distance, thus repeating the
feature of the last and succeeding stages in this particular. In
the region of the last (12th) protovertebra, however, the cord of
cells constituting the Wolffian duct at this stage is now con-
tinuous with the intermediate cell mass at certain intervals.
Comparing the sections through the 12th segment of this stage
with those just behind the 11th protovertebra of the previous
stage, it is seen that the Wolffian duct has enlarged, and by a
downgrowth of cells from it, with which probably is connected
an upgrowth from the intermediate cell mass, has become in
certain places connected with the intermediate cell mass. These
secondary connections constitute the commencing tubules of this
part of the Wolffian body.
In a chick with thirteen protovertebree an advance precisely
similar to that characterising the previous stage has taken place,
i.e. the Wolffian duct has become connected with the inter-
mediate cell mass in the 13th segment (fig. 7), and behind
this point is free from adjacent structures.
In a chick with fourteen or fifteen protovertebre the process
of development remains the same. So that im a chick with
fifteen segments the following is the condition of the Wolffian
duct :—It extends from the 7th to the 15th segment as a solid
cord of cells, connected at intervals with the peritoneal epithe-
lium by the commencing Wolffian tubules; behind the 15th
segment it extends for a short distance asa free cord. The further
development differs from that just recorded in this important
particular ; the duct does not become connected with the inter-
mediate cell mass of the newly-formed last segment, but remains
separate for a considerable interval of time (till towards the end
of the third day) from it. In other words, the formation of
434: ADAM SEDGWICK.
the Wolffian tubules and their connection with the Wolffian
duct is deferred behind the 15th segment.
To sum up the developmental changes above recorded, the
Wolffian duct arises as a continuous ridge of cells projecting
from the intermediate cell mass towards the epiblast in the
region of the 7th to 11th protovertebre inclusive. This ridge
separates from the intermediate cell mass from before backwards,
remaining, however, connected with it at intervals by the rudi-
mentary Wolffian tubules. Meanwhile, from the hind end of it
there grows back a cord of cells independent at first of the
adjacent structures, but immediately on the formation of the
hinder segments becoming connected with the intermediate
cell mass of each segment in turn. This happens as far. back
as the 15th segment; behind this point it grows back as a
solid cord, which does not become connected with the inter-
_mediate cell mass until the tubules of the Wolffian body have
made considerable advance in their development.
Figs. 1—7 are meant to illustrate the above method of develop-
ment. Figs. 1—5 are from the 10th segment of chicks, with
ten, twelve, thirteen, and fourteen protovertebre respectively.
They are all taken through points where the Wolffian duct remains
attached to the peritoneal epithelium, z.e. through a rudimentary
tubule, excepting fig. 4, which is from a section close to fig. 3,
and shows the condition of things in one of the intervals between
the points of continuity.
Fig. 6 is taken from a section just behind the last segment of
a chick with twelve segments, and shows the complete inde-
pendence of the Wolffian duct.
Fig. 7 is from the 13th segment of a chick with thirteen seg-
ments, 7.e. from the same region as fig. 6, and it shows the con-
nection which has become established between the Wolffian
duct and the intermediate cell mass by a mutual growth of these
structures. val
Fig. 8 is from the 16th segment of a chick with twenty-two
protovertebre, and is illustrative of the fact derived from an
inspection of all the sections of the segment, that the Wolffian
duct is independent of the peritoneal epithelium. From the
15th segment the Wolffian duct grows back independently to
the cloaca, into which it eventually opens, and a lumen appears
in it from before backwards.
In fig. 11, taken from a chick at the end of the third day, it
is still distinct from the now considerably developed Wolffian
tubule (w.?.).
For purposes of description I shall divide the Wolffian body
into three regions—(1) The part found within the limits of the
7th—11th segments inclusive ; (2) the part found within the
WOLFFIAN DUCT AND BODY IN THE CHICK, 435
12th—15th segments inclusive ; (3) that found behind the 15th
segment.
In a previous paper! I have described at some length the
early development of the Wolffian body behind the 16th segment,
and I have there shown that that part may be divided into two
parts, each characterised by a peculiarity in the early develop-
ment. In this paper I shall make but little reference to the
development of the Wolffian body in this region, confining
myself almost entirely to that part lying within the area of the
7th to the 15th segments inclusive.
Development of Wolffian Tubules in region of 1th—11th
Segments.
The Wolffian tubules and Wolffian duct in this region attain
but a slight development. They may almost be said to have
reached their highest point at the stage with fourteen proto-
vertebre, the only difference in later stages being the develop-
ment of a lumen in them. The lumen in the tubule may
acquire an opening into the Wolffian duct in some cases. In
this case the string of cells seen in fig. 5 becomes very short,
and the Wolffian duct appears as a narrow groove in the peri-
toneal epithelium. This state of things is usually found in
chicks with from nineteen to thirty-two protovertebre.
The Wolffian duct in this region exhibits great variations in
calibre, and in later stages parts of it appear to atrophy, and
isolated portions are found connected with rudimentary tubules.
An enlarged section of the Wolffian duct in front is nearly
always found as Gasser® has described. The duct and tubules
in this region appear entirely to atrophy in chicks with more than
thirty-five protovertebre.
I have not thought it worth while to preserve figures of the
duct and tubules in this region of the Wolffian body after their
first appearance, as the arrangement just described may be easily
observed in sections of an embryo chick of the third day.
The interest in the development of this region lies in the fact
of the continuity of development of the Wolffian tubules and
Wolffian duct. It has always appeared to me astonishing that
the Wolffian duct developed as a continuous ridge from the inter-
mediate cell mass, which, from our knowledge of Elasmobranch
development, may be called the peritoneal epithelium, should
entirely separate from it and then secondarily become connected
with it by the tubules of the Wolffian body. My investigations,
which have been made with some care on a large number of
I Loe. cit. 2 Loc. cit.
436 ADAM SEDGWICK.
chicks of all ages from nine to thirty protovertebre, have
entirely convinced me that the usual statements on this point are
not true, and show to my mind most conclusively that the duct
and tubules of the Wolffian body in the region in question do
develop in continuity, precisely as do the duct and peritoneal
openings of the head-kidney in most Ichthyopsidan types.
The number of rudimentary tubules in each segment of this
region I have not determined precisely. They occur as often
as not between the segments, and there seems to be about two for
each segment. In the seventh segment I have never seen more
than one.
Before proceeding to give an account of the further develop-
ment in the next region, I will briefly refer to the points in
which my observations differ from those of previous observers
on the development of the Wolffian duct.
Gasser’s account of the development of the Wolffian duct is
the most recent and exact. In his valuable paper will be found
a complete account of the literature of the subject, to which I
need not further refer.
“The first trace of it which he finds is visible in an embryo
with eight protovertebre as a slight projection from the inter-
mediate cell mass towards the epiblast in the region of the three
hindermost protovertebree. In the next stage with eleven pro-
tovertebre, the solid rudiment of the duct extends from the 5th
to the llth protovertebre ; from the 8th to the 11th
protovertebrze it lies between the mesoblast and epiblast, and is
quite distinct from both, and Dr. Gasser distinctly states that
in its growth backwards from the 8th protovertebre the
Wolffian duct never comes into continuity with the adjacent
layers. In the region of the 5th protovertebraee, where the
duct, &c., was originally continuous with the mesoblast, it has
now become free, but is still attached in the region of the 6th
to the 8th. In an embryo with fourteen protovertebre the
duct extends from the 4th to the 14th, and is now free between
epiblast and mesoblast for its whole extent.”
The points in which the preceding account differs from that
of Dr. Gasser’s briefly are :
1. The position of the continuous ridge of the Wolffian duct.
2. The subsequent complete isolation of the duct in the
region of the ridge.
3. The independence of the backward growth of the duct in
the 12th to the 15th segment.
I have never seen any trace of the Wolffian duct in front of
the 7th segment, and in all the chicks I have examined I find
1 © Arch. fiir Mic. Anat.,’ vol. xiv.
WOLFFIAN DUCT AND BODY IN THE CHICK, 437
that the continuous ridge extends from the 7th to the 11th
segments.
With regard to Gasser’s statement of the complete isolation
of the duct in the anterior region from the intermediate cell
mass, I can only say that my observations point to an entirely
different conclusion.
Thirdly, I differ with him in his statement that the duct in
the growth back from the attached extremity does not come
into relation with adjacent structures.
As stated above, it seems to me that for the space of four
segments the small cord of cells which grows back from the hind
end of the ridge, does almost immediately become connected
with the intermediate cell mass.
Development of the Wolffian Duct and Body from the 12¢h—15th
Segment.
I now pass to the most interesting point which has turned
up in my investigations on the excretory system of the chick.
In a paper by Mr. Balfour and myself in the ‘ Quart. Journ. of
Micr. Science,’ vol. xix, describing the development of what we
believed to be a rudimentary head-kidney in the chick, we drew
attention to a structure which so closely resembled the glomeru-
lus! of the head-kidney of the Ichthyopsida that we identified it
as an homologous structure.
Gasser has also independently discovered and similarly iden-
tified this structure.
In the paper just referred to no attempt was made to trace the
development of this glomerulus, but it was merely described as
it appeared at the time of its greatest development.
The following description is taken from that paper :
“Tn the chick the glomerulus is paired, and consists of a
vascular outgrowth or ridge projecting into the body cavity on
each side at the root of the mesentery. It extends from the
anterior end of the Wolffian body to the point where the fore-
most opening of the head-kidney commences. We have found
it at a period slightly earlier than that of the first development
of the head-kidney....In the interior of this body is seen a
stroma with numerous vascular channels and blood-corpuscles,
and a vascular connection is apparently becoming established, if
it is not so already, between the glomerulus and the aorta. The
stalk connecting the glomerulus with the attachment of the
1 T have already given a preliminary account of the development of this
structure in the ‘ Proc. Cambridge Phil. Soc.,’ May 3, 1880.
2 *Sitzungsberichte der Gesellschaft zur Bedford d. gesam. Naturwiss.,’
No. 5, 1879.
438. ADAM SEDGWICK.
mesentery varies in thickness in different sections, but we believe
that the glomerulus is continued unbroken throughout the very
considerable region through which it extends. This point is,
however, difficult to make sure of, owing to the facility with
which the glomerulus breaks away. At the stage we are
describing no true Malpighian bodies are present in the part of
the Wolffian body on the same level with the anterior end of the
glomerulus, but the Wolffian body merely consists of the Wolffian
duct. At the level of the posterior part of the glomerulus this
is no longer the case, but here a regular series of primary Mal-
pighian bodies is present, and the glomerulus of the head-kidney
may frequently be seen in the same section as a Malpighian
body. In most sections the two bodies appear quite discon-
nected, but in those sections in which the glomerulus of the
Malpighian body comes into view it is seen to be derived from
the same formation as the glomerulus of the head-kidney.”
The point which is left in doubt in the above description,
viz. as to whether the glomerulus constitutes a continuous
structure, is at once decided by a study of its development.
I may here state that it is not a continuous structure, but
consists of a series of external glomeruli, each of which corre-
sponds and is continuous with the glomeruli of the Malpighian
bodies found in this part of the trunk.
The first development of the Wolffian tubules in the region
under consideration has already been described. They appear
as outgrowths from the Wolffian duct meeting outgrowths from
the intermediate cell mass immediately on the formation of the
segment in which they are placed ; so that in a chick with fifteen
protovertebree the Wolffian duct is connected with the inter-
mediate cell mass by a certain number of cell cords in the 12th,
13th, 14th, and 15th segments. ;
The duct and cords, which have at first rather an irregular
outline, soon become well-defined compact structures.
Fig. 12, taken from the 12th segment of an embryo with
twenty-two segments, represents the condition of things at this
age.
The Wolffian tubules in this region are derived from two
distinct structures—(1) the outgrowth from the Wolffian duct ;
(2) part of the intermediate cell mass.
The intermediate cell mass is at first continuous with the
peritoneal epithelium in every section; but, as described in a
previous paper, this connection soon becomes lost at certain
points (fig. 9), and maintained at others (fig. 10). Figs. 9 and
10 are contiguous sections through the 15th segment of a chick
with twenty-two segments, showing this point. At these points,
where the continuity is retained, a peritoneal funnel is subse-
WOLFFIAN DUCT AND BODY IN THE CHICK. 439
quently formed by the development of a lumen extending from
the body cavity into the intermediate cell mass.
The features of the stage of development now reached are well
known ; it is that of the S-shaped cords of cells which have been
so often described. In the adjoining woodcut is represented part
of one of these S-shaped strings, showing clearly the above
ue
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Transverse Section through the Trunk of a Duck Embryo with about
twenty-four Mesoblastic Somites.
am. amnion ; so. somatopleure ; sp. splanchnopleure ; wd. Wolffian duct ;
st. segmental tube; ca.v. cardinal vein; ms. muscle-plate; sp.g. spinal
ganglion; sp.c. spinal cord; cA. notochord ; ao. aorta; Ay. hypoblast.
features of a tubule, &c., viz.—(1) the Wolffian duct, in which a
lumen has appeared ; (2) the outgrowth from it to the inter-
mediate cell mass forming the upper limb of the S; (3) the
44.0 ADAM SEDGWICK.
intermediate cell mass with the commencing lumen from the body
cavity.
‘ah the next section the intermediate cell mass is not
connected to the peritoneal epithelium.
In chicks of gradually increasing number of protovertebre this
cavity in the intermediate cell mass gradually becomes more
marked (figs. 13, 14), and extends into that part of it imme-
diately behind the peritoneal connection (fig. 15).
Figs. 13, 14, and 15 are three successive sections through the
13th segment of a chick with about thirty segments, showing
the features of a tubule at this stage.
The Wolffian duct is connected with the lower end of the in-
termediate cell mass in all the three sections. A distinct lumen
has appeared in the intermediate cell mass which opens into the
body cavity in front (figs. 13 and 14), but is separate from the
body cavity in the hindermost section (fig. 15).
Comparing these figures with figs. 9 and 10 it is seen that
fig. 18 or 14 corresponds to fig. 9 in the fact of the continuity
between the intermediate cell mass and peritoneal epithelium ;
while fig. 15 corresponds to fig. 10, in both the continuity
having been lost. The difference between them consists in the
presence of a distinct lumen in the older series, opening into
the body cavity, and continued behind into the part of the
intermediate cell mass which has separated from the peritoneal
epithelium. This part, marked 2. ¢. m. in fig. 15, will in the
next stage become converted into that part of the tubule in
which a Malpighian body is developed, while the anterior part,
which is open to the body cavity, will widen out considerably,
and give rise to a wide peritoneal funnel,
In fig. 11 is represented a section through a developing
Wolffian tubule in the hinder part of the Wolffian body. The
tubule (w. Zé.) in this section precisely resembles the part of the
tubule (2. c. m.) represented in fig. 15. Supposing the anterior
part of w. ¢1. were open to the body cavity it would almost be a
repetition of the anterior tubule, save in the fact that it is not yet
united to the Wolffian duct. But the hinder tubule (fig. 11)
does not develop until after the intermediate cell mass has sepa-
rated from the peritoneal epithelium, 7. e. subsequent to the
obliteration of the rudiment of the peritoneal funnel.
Not only do the Wolffian tubules in the region of the 12th
to 15th segments develop a lumen while still continuous with the
peritoneal epithelium, but further, a glomerulus appears in them
while still open to the body cavity; and this glomerulus not
only appears in the hinder part of the tubule (fig. 15) which
has separated from the peritoneal epithelium, but also in the
anterior part (figs. 13 and 14) where it is open to the body
WOLFFIAN DUCT AND BODY IN THE CHICK, 441
cavity. This is at once clear on inspection of figs. 16, 17, 18.
These figures are taken from the 13th segment of a chick with
thirty-four protovertebre. There was a section not figured
between fig. 17 and 18, otherwise the sections are successive,
fig. 16 being the anterior.
Tn fig. 16 is seen the commencement of the peritoneal funnel
as a bay lying between the Wolffian duct and mesentery.
In fig. 17, a glomerulus (g/.) has appeared projecting into this
bay. In the next section, not figured, the bay was almost
closed up by an approximation of its edges, while in fig. 18 the
bay is completely shut off from the body cavity, and we have a
section of a true Malpighian body with its contained glomerulus.
Fig. 18 clearly corresponds to fig. 15 of the previous stage,
while fig. 17 corresponds to fig. 14, the difference being that a
distinct cellular projection (g/.) has appeared at the point where
the projection of cells from the Wolffian duct joins the inter-
mediate cell mass.
I have given a diagram (fig. 22) representing an ideal longi-
tudinal dorso-ventral section through two of these Wolffian
tubules at this stage. This diagram has been made from a study
of many embryos showing the development of the external
glomerulus.
The open peritoneal funnel is represented at p. 7, the arrow
pointing into it. Through it is projecting the anterior part of
the glomerulus (g/.), that part which I shall call the external
glomerulus. A transverse section through this part would
give the appearance represented in fig. 17.
Into the closed hinder part of the tubule (mé.) is projecting
the hinder part of the glomerulus (2. g/.), which I shall call the
internal glomerulus. It was. not possible to represent satis-
factorily in this diagram the Wolffian duct, which, obviously
from its position in transverse section, would not be seen in a
longitudinal section passing through the attachment of the
glomerulus.
In fig. 23 is represented somewhat diagrammatically a trans-
verse section through a chick with thirty-three protovertebre,
i.e. from a slightly younger embyro than that from which
figs. 16—18 were taken, in which the cord of cells connecting
the Wolffian duct with the cavity of the glomerulus had acquired
a distinct lumen, the cavity of the Wolffian duct being here
distinctly continuous with that of the bay in which is placed
the rudimentary external glomerulus, and so with the body
cavity. At subsequent stages this part of the tubule appears to
persist, but only in a rudimentary fashion.
The next stage which I propose to describe was found in a
442 ADAM SEDGWICK.
chick in which thirty-six protovertebre could be counted, but
possibly there were more.
The glomerulus has grown immensely (figs. 19, 20, 21), and
has now acquired the peculiar histological features which
characterise it at the time of its greatest development, and which
have already been described in a former paper.
Anteriorly the bay has widened out considerably (fig. 19),
and the glomerulus (e. g/.) projects directly into the body
cavity. Posteriorly the bay remains deep (figs. 20, 21), and the
glomerulus almost completely fills it and projects beyond it into
the body cavity. In sections behind fig. 21 there was seen a
fairly well-developed internal glomerulus.
The edges of the bay are gathering round the glomerulus pre-
paratory to fusing with it, and so closing up the peritoneal
funnel and dividing the glomerulus completely into two parts,
the internal vascular tissues of which, however, are continuous.
In this stage the epithelial covering of the external glomerulus
(ce. gi.) was distinctly, as in the previous stage, continued behind
directly into that covering the posterior internal glomerulus.
When, however, the peritoneal funnel closes by the comple-
tion of the process commencing in figs. 20 and 21, this epithelial
continuity is lost, and we have the final stage of the glomerulus,
the last which I have observed, in which the separation above
described is complete, so that in this stage, which is that of the
greatest development of the external glomerulus, and corre-
sponds with the commencing formation of the head-kidney, the
glomerulus belonging to one tubule is divided into three parts.
(1) An anterior! part projecting into the body cavity. ‘This
corresponds to a further development of fig. 19.
(2) A middle part, continuous with (1), also projecting
freely into the body cavity, but also connected by vascular
structures with an internal glomerulus. This part is figured in
fig. 26, and corresponds to a further development of the part
from which fig. 20 and 21 were taken.
(3) A posterior part, in which there is no external glomerulus,
but merely an internal one belonging to a true Malpighian
body of the mesonephros, which I have not thought it neces-
sary to figure in this or the previous stage. It is a further
development of fig. 18. This stage, which may be observed
about the middle of the fourth day of incubation, brings to a
close my observations on this extraordinary structure. It appears
that in the chick the stage just described is that of the greatest
development of the external glomerulus. In the duck, however,
T have often met with it even larger and more developed, and
\ Fig. E, Pl. Il, in the paper on the “ Head-Kidney of the Chick,”
* Quart. Journ. Mic. Sci.,’ vol. xix.
WOLYFIAN DUCT AND BODY IN THE CHICK, 443
it appears to me after its separation from the internal glome-
rulus to get an independent growth, and while the latter is
undergoing atrophy to become larger and extend itself posteriorly,
so as almost to overlap the external glomerulus of the next
tubule.
With regard to the number of the external glomeruli in the
chick and the exact limits of their occurrence, the following is
briefly what I have been able to make out in a chick with thirty
protovertebree :
In the 11th segment there are two rudimentary tubules
running from the Wolffian duct to the peritoneal epithelium.
At the point of attachment of these there is a small rudiment of
the external glomerulus, visible for only one section in each
case.
In the 12th segment there is at the beginning a Wolffian
tubule and a well-marked external glomerulus extending through
three sections. At the hind end of the 12th segment and
beginning of the 13th there is an external glomerulus for three
sections continued into part of the segmental tube behind, in
which an internal glomerulus will subsequently be developed.
In the 13th segment there is an external glomerulus for three
sections.
In the 14th segment there are two segmental tubes with
developing external glomeruli.
In the 15th segment no external glomeruli appear to be
developed, the segmental tubes being already separated from
the peritoneal epithelium.
Tn later stages only the three or four hindermost of the above
external glomeruli appear to develop further. The anterior
glomeruli soon atrophy with the adjoining tubules and duct.
In the duck a much greater number become developed,
and they may be seen in the anterior segments after their
respective tubules have entirely atrophied.
The bearing of the developmental processes above recorded on
any hypothesis as to the phylogenetic history of the vertebrate
excretory system I propose to examine in the second part of this
paper (pp. 460—462 ; 464).
Parr II. A Discussion of the Vertebrate Excretory System in
General.
The most peculiar feature of the excretory system of the
vertebrata is the presence of three more or less distinct parts, the
pronephros, the mesonephros, and the metanephros or kidney
proper. In the following pages my object will be to explain the
relation of these parts, more especially those of the pronephros
VOL, XXI.—NEW SER. GG
444 ADAM SEDGWICK.
and mesonephros, and to show that they have arisen as differen-
tiations of a primitively uniform structure.
For this purpose it is necessary briefly to recapitulate the
more important features in the development which have a
bearing on my argument.
Segmental Duct and Pronephros.
The first part of the excretory system to make its appearance
is always a duct. This duct has received various names, but its
homology in different forms is undisputed. I shall call it the
segmental duct.
In the chick the segmental duct is commonly known as the
Wolffian duct.
All the Ichthyopsida whose development is known, with the
exception of Elasmobranchs, possess a structure called the head-
kidney or pronephros. The pronephros when present always
develops in continuity with the anterior end of the segmental
duct.
In the Amphibian the segmental duct arises as a groove of
the parietal peritoneum, just ventral to the place where the body
cavity is connected with the cavities of the muscle plates. This
groove, which arises first of all anteriorly just behind the
branchial region, is continued for a certain distance backward.
It soon, however, becomes constricted into a canal lying between
the ectoderm and parietal peritoneum. This constriction has
been described as taking place in the following manner :—It
first appears in the middle region of the groove, giving rise to a
canal opening into.the body cavity in front and behind. It
then is continued backwards until the groove is completely con-
verted into a canal behind, which soon acquires an opening into
the cloaca. Anteriorly the wide opening meanwhile is divided
up into two,! three,” or four® openings, according to the species.
The canal immediately behind the last of these openings
becomes coiled and placed on the same level but ventral to the
openings. The part of the body cavity into which the openings
of the segmental duct pass widens out, a vascular projection—
the glomerulus—from the dorsal inner wall is formed, extending
uninterruptedly from opposite the anterior opening of the seg-
mental duct to as far back as the posterior. The dilated section
of the body cavity in which the glomerulus lies, and into which
the segmental duct opens, is partially separated from the rest of
the body cavity. The whole structure, including openings of
duct, ventral coiled part of duct, glomerulus, and dilated part of
body cavity, is known as the pronephros, The number of open-
' Urodela. 2 Anura. 3 Cecilia.
~
WOLFFIAN DUCT AND BODY IN THE CHICK, 4.45
ings from the segmental duct into the body cavity corresponds
with the number of segments through which the pronephros
extends.1
With its excretory system in this condition the young
Amphibian is hatched. Fundamentally the head-kidney retains
the above structure, increasing only in size until it begins to
atrophy, an occurrence which takes place on the development
of the mesonephros.
This method of development of the segmental duct and pro-
nephros is fundamentally repeated in other animals which possess
a pronephros.
About the marsipobranch development very little is known.
Fiirbringer (loc. cit.), quoting W. Miller and his own observa-
tions, makes the following statements for Petromyzon :—In the
earliest stage which has been observed there was present at
about the level of the heart a groove in the parietal peritoneum,
which leads behind into a duct, which eventually, by a backward
growth, reaches the cloaca and opens into it. The anterior
groove or opening of the duct soon becomes divided up into
four openings.
In the young Ammoceetes there is present a pronephros made
up of a complicated coiled duct and four or five openings into
the body cavity, opposite which is placed a vascular glomerulus ;
the whole structure extends over four or five segments.” The pro-
nephros atrophies in the adult.
In Myxine nothing is known of the development, but in the
adult a pronephros has been described, which, however, is not
functional in old individuals (adult ?), as in them it has lost its
connection with the backward continuation of the segmental
duct.
It? consists of the segmental duct, which gives off dorsally a
number of diverticula, in which are found glomeruli, and ven-
trally a number of coiled canals, which open apparently into
the pericardial cavity.
The fully-formed proenephros of Petromyzon then resembles
in structure very closely that of Amphibia, while the pronephros
of Myxine differs in certain important points.
The Teleostei possess a pronephros, which persists as a large
organ in the adult. It develops in connection with the seg-
1 Fiirbringer, ‘ Morph. Jahrbuch,’ Bd. 3, p. 5.
2 Scott, in a recent paper (‘ Morph. Jahrbuch,’ vol. viii), states that the -
segmental duct in Petromyzon, develops as a solid cord of cells from the
somatic mesoblast, which subsequently becomes hollow. The peritoneal
openings of the head-kidney are developed as outgrowths from the anterior
end of this duct to the body cavity.
3 * Jenaische Zeitschrift,’ vol. vii, 1873.
446 ADAM SEDGWICK.
mental duct precisely as does the pronephros in Amphibia. The
only difference between the two is that in Teleostei the segmental
duct has never more than one anterior opening, and the part of
the body cavity into which it opens, and in which the glomerulus
lies, is completely constricted off from the rest of the body cavity,
and comes to resemble exactly an enormous Malpighian body.!
I may here sum up the common features characterising the
ontogeny of the pronephros and its duct (segmental duct) in
all the forms of the Ichthyopsida in which the development is at
all known:
1. The segmental duct arises first as a ridge from the
parietal peritoneum. ‘This ridge usually contains a diverticulum
from the body cavity, and is continuously constricted off to form
a duct.”
2. Except anteriorly, where the constriction only takes place
at intervals, leaving the openings of the pronephros (except in
Teleostei, where there is only one opening).
8. These openings correspond in number with the segments
which the pronephros occupies.®
4, A vascular structure, called glomerulus, is formed, pro-
jecting on each side of the aorta into a specialised dilatation of
the anterior part of the body cavity. Myxine forms a peculiar
exception to this otherwise universal fact.
5. This dilated part of the body cavity may become partially
or completely separated off to form a capsule, into which the
glomerulus projects and the anterior end of the segmental duct
opens.
j 6. The pronephros in all those Ichthyopsida in which it is
found attaims a functional development, but is usually only
active during a period intervening between the hatching and the
attainment of full maturity, z.¢. it only functions in the larva.
In Elasmobranchs, which do not, so far as is known, possess
a pronephros, the segmental duct arises as a solid ridge from the
somatic layer of the intermediate cell mass in the anterior region
of the trunk. From this ridge there grows back a column of
cells to the cloaca. On the development of a lumen the seg-
mental duct, with its peritoneal opening, is established. The
duct develops quite independently of adjacent structure behind
1 There is a functional head-kidney in adult Ganoids. It appears to
be formed on the Teleostean type (vide Balfour, ‘Comp., Embryology,
vol. 2, p. 51).
le Patotiyion, Scott (see note, p. 445) states that this duct arises as
a solid rod of cells, which secondarily becomes connected with the body-
cavity epithelium, to form the pronephric funnels. This account, in my
opinion, needs confirmation.
5 ¢Fiirb.,’ p. 5, p. 42.
WOLFFIAN DUCT AND BODY IN THE CHICK. 447
the point of its original attachment, and does not unite with
the segmental tubes till considerably after its first development.
The difference in the development of the segmental duct in
the forms possessing a pronephros and in Elasmobranchs is only
one of degree.
In both cases it at first arises as a projection, either solid or
containing a diverticulum from the body cavity, from the
parietal peritoneum just ventral to the muscle plates ; but in the
one case this groove has a greater longitudinal extension than
in the other. In all probability the hinder part of the seg-
mental duct is in all cases formed by an independent growth
from the hind end of this groove.
Amongst the Amniota the chick is the type in which the
development of the segmental duct has been most carefully
examined.
In the chick it arises as in Amphibia as a projection (solid in
the chick) from the parietal mesoderm just ventral to the
muscle plates; and the extent of the ridge is the space occupied
by five segments.
This ridge is constricted off at intervals from the intermediate
cell mass, but remains attached at certain points. The hind end
of the duct is formed by a growth back from the hind end of
this ridge, which takes place independently of adjacent
structures.
The question now presents itself: are these structures at the
anterior end of the segmental duct in the chick, which so closely
resemble in development the openings of the Ichthyopsidan
head-kidney, homologous with that head-kidney ?
To a consideration of this question I shall return:
Mesonephros.
The mesonephros obtains a large development in all the
groups of the Vertebrata; but it does not persist as an excre-
tory organ in the adult of the Amniota.
It develops in three very markedly distinct ways.
The first of these characterises the Elasmobranchii.
The second the Amphibia, Teleostei, Ganoidei, Marsipo-
branchii. |
The third the Amniota.
The Development of Mesonephros in Elasmobranchii.
The segmental tubes of Elasmobranchii were originally de-
scribed by Balfour as arising as solid diverticula of the peritoneal
epithelium. An examination of Balfour’s specimens led me,
however, to conclude that they originated as specialised parts
of the body cavity, viz. from the canals in the intermediate
448 ADAM SEDGWICK,
cell mass which connect the muscle plate cavities with the general
body cavity; and Balfour has now given his adherence to this
view (‘Comp. Embryology,’ vol. 2, p. 570).
These canals having lost their connection with the body cavity
of the muscle plates acquire an opening into the segmental duct,
and differentiate’ into the typical Wolffian tubules. The connec-
tion with the general body cavity may or may not be retained in the
adult. The secondary tubules develop as outgrowths from that
part of the primary tubules, which will give rise to a Mal-
pighian capsule. These outgrowths grow forward and even-
tually acquire an opening into the terminal portion of the
tubule of the segment in front. Later they loose their connec-
tion with the Malpighian capsules, though a rudiment of this is
sometimes retained as a solid cord of cells.
The method of development of the secondary, tertiary, &c.,
tubules has not been followed.
The primary tubules open into the segmental duct very shortly
after the latter has acquired an opening into the cloaca.
The formation of the Malpighian bodies and the outgrowths
from them to form secondary tubules occur later.
For a full account of the development of the mesonephros
in Elasmobranchs I must refer to the works of Balfour and
Semper, to whom we owe the whole of our knowledge.
Development of the Mesonephros in the remainder of the
Ichthyopsida.
As a type of this development I will take an Amphibian,
Salamandra, in which animal it has been more completely
elucidated by Fiirbringer than in any other.”
Fiirbringer describes the formation of the mesonephros as
taking place entirely during larval life; no trace of the gland
being seen in the newly hatched larva. It arises as a series of
ingrowths of the peritoneal epithelium, which soon become
separate from the latter. The primary tubules are hollowed out
in the cell masses so formed independently both of the body
cavity and segmental duct (Wolffian duct), but subsequently
they acquire an opening into both.
The secondary tubules arise in a blastema, the origin of
which is not clear, but is apparently derived from the just
mentioned serial ingrowths. They acquire an opening into
the collecting part of the primary tubule and into the body
cavity. The remaining dorsal tubules have an equally obscure
origin.
' « Klasmobranch Fishes,’ p. 260 e¢. seg.
= Loe. cit.
WOLFFIAN DUCT AND BODY IN THE CHICK. 449
As the mesonephros becomes more developed the pronephros
retrogrades, and: is eventually entirely, as far as its function is
concerned, replaced by the former.
The development of the mesonephros in Teleostei, Marsi-
pobranchii, Ganoidei, is similary described as taking place in the
free young (larva) from strings of cells derived from the peri-
toneal epithelium. In Marsipobranchii as in Amphibia the young
are hatched with a functional pronephros, and no trace of the
mesonephros; but the former is, in the further growth of the
young animal, gradually replaced functionally by the latter, and
more or less retrogrades. In the Teleostei, however, and
Ganoidei, it persists with the mesonephros as an important
functional organ in the adult. In some Teleostei the pronephros
is the only functional aduit kidney, the mesonephros not being
developed.
I have made some observations on the development of the
mesonephros in the Frog (Rana temporaria), Salmon and Stur-
geon, and my observations lead me very strongly to doubt whether
Fiirbringer and other observers are right in describing the origin
of the cells which give rise to the mesonephros as actual
ingrowths from the peritoneal epithelium.
In the case of the Frog this is certainly not the case. In
fig. 25 is represented a section through a Tadpole of 11 mm.,
showing the first trace of the cells (k B) from which the Wolffian
tubules arise. At their first appearance they are independent
of the peritoneum, and only secondarily become connected
with it. Fiirbringer figures from the Salamander a section
in support of his statement ; I have also seen such appearances
in the Tadpole, but in this animal these strings are only found
in that part of the animal in which, I am confidently able to state,
no Wolffian tubules are ever developed. I have examined and
compared segment with segment of Tadpoles of various ages,
and have never found these strings of cells developing into
Wolffian tubules. The cell strings appear to me to arise from a
blastema of cells developed zm sitd becoming connected with the
peritoneal epithelium, and they are, no doubt, rudimentary
tubules.
Fiirbringer in his paper gives no evidence of the origin of
these cells from the peritoneal epithelium, except a drawing of
a stage in which the blastema is connected with the peritoneal
epithelium.’ I have also seen this stage, as mentioned above,
' Gotte also, in his latest writings on the subject, agrees with Fiirbringer
as to the origin of the cells which give rise to the mesonephros. But 1 may
draw attention to the fact that Gotte has held three views on this point,
the last of which did not appear (see Firbringer, loc. cit.) till 1875, i.e.
after the publication of Balfour and Semper’s works on ‘ Elasmobranchi,’
450 ADAM SEDGWICK.
in my sections of the Frog, but have completely failed to
find the earlier stages of this ingrowth. One would expect to
see it preceded by a thickening of the very flat cells lining the
body cavity at this point; one would hardly expect the flat
cells so specialised to form the lining of the body cavity of
the young larva suddenly, and without showing any change to
begin to grow inward. Further, if the cell cords described by
Fiirbringer in the Salamander are really only rudimentary struc-
tures belonging to the anterior part of the mesonephros, as is
certainly the case in the Frog; and if the process which Fiir-
bringer describes for the posterior part of the mesonephros of
the Salamander takes place for all fully-developed parts of the
mesonephros, as is the case in the Frog, then part of the diffi-
culty caused by the peculiar secondary development of the
peritoneal funnels disappears. In other words, I believe Fur-
bringer has made a mistake, precisely similar to that which was
made about the development of the Avian Wolffian body. He
has seen in the anterior part of a young larva the cell cords
mentioned above ; which were present at a time when there was
no trace of the posterior part of the mesonephros. He has also
seen in the hinder part of older larve the blastema of cells
separate from the peritoneal epithelium from which the Wolffian
tubules arise. Finally, he has connected these two conditions,
which are, as I believe, found in different regions of the trunk,
and has concluded that the cell strings of the anterior part have
separated from the peritoneal epithelium and given rise to the
cell masses of the posterior part which really develop indepen-
dently of the peritoneal epithelium, and eventually give rise to
the Wolffian tubules.
My observations on Teleostei lead me, for similar reasons, to
assert an origin, im sité, of a continuous blastema, which later,
breaking up, will give rise to the Wolffian tubules.
On the other hand, the older observers, including Vogt and
Rosenberg for Teleostei, Rathke, Johan. Miiller, Reichert, Vogt,
for Amphibia,” are quoted by Fiirbringer as asserting an origin
of the tubules as a series of excavations in a blastema of cells
lying just internal to the segmental (Wolffian) duct. And it
seems to me that the older observers were,® as in their state-
ments concerning the development of the mesonephros in the
chick, not far from the truth. In the Sturgeon my observations
point to a similar conclusion; in the just-hatched young a few
mesoblast cells are seen lying internal to the segmental duct.
These, at a later stage, are replaced by a more compact mass of
1 © Firbringer,’ loc. cit., p. 46.
2 Ibid., loc. eit., p. 12.
3 Self, ‘ Quart. Journ. Mic. Sci.,’ April, 1880.
WOLFFIAN DUCT AND BODY IN THE CHICK. 451
cells, occupying the position of which, in a still older animal,
Wolffian tubules are seen.!
The point I wish to insist upon is that sufficient proof of an
actual ingrowth of cell from the peritoneal epithelium has not
been given; but that it is much more probable that the kidney
blastema arose iu sit#, in some cases perhaps in continuity with
the peritoneal lining, and in other cases independently of it,
but soon becoming united with it to form the nephrostomata.
The development of the mesonephros in the Amniota has been
most fully elucidated in the chick.”
Ina recent paper I have described the development of the
posterior Wolffian tubules from a continuous blastema of cells
derived from the intermediate cell mass; and in the first part
of this paper that of the anterior tubules from the cell cords
left connecting the Wolffian duct and intermediate cell mass.
Further, in the chick there is a kind of intermediate method
of development of the tubules of the 12th—15th segments (see
above).
The question here again recurs which was asked before: Are
these tubules of the anterior part of the Avian Wolffian body
really tubules of the Wolffian body, or have they something
to do with the head-kidney? Fora discussion of this question
I must refer below to p. 460.
The Metanephros.
In a recent paper? I have attempted to show that the me-
tanephros, which is found only in the Amniota, is developed from
a blastema of cells which arises continuously with but behind
the blastema from which the Wolffian tubules develop.
Although the blastema which will give rise to the greater part
of the metanephros arises at a comparatively early stage in de-
velopment, still it is not till a much later stage that it shifts its
position, and begins to show signs of developing into the Wolffian
tubules. This late development of the kidney, which in this
point to a certain extent resembles the Amphibian mesonephros,
is a very remarkable fact. I shall return to it again.
I have thus run over very rapidly the most salient features
in the development of the various parts of the Vertebrate excre-
tory system, so far as it is at present known to us. I now turn to
" Balfour has recently described the existence of solid cords of cells,
connected wfth the peritoneal epithelium, in the anterior part of the meso-
nephros of the sturgeon (‘Comp. Embryology,’ vol. ii, p. 581). The
origin of these cords is not clear, neither is it certain that they undergo
full development.
2 Loe. cit.
3 Loe. cit.
452 ADAM SEDGWICK.
a consideration of the bearing which these facts have upon any
hypothesis as to the phylogenetic connection of these various
organs.
But, before so doing, it will be well to consider the nature of
the problem which presents itself. It is universally admitted
that the Craniata have had a common ancestor. The problem
to be solved is contained in these questions: What was the
structure and development of the excretory system of that an-
cestor? How has it been modified to produce the excretory
organs which we see in Vertebrates now living?
I am but too well aware how complicated and difficult the
problem is, and how insufficient are the data we at present
possess to enable us to solve it. Of the two sources (geology
and embryology) from which we can hope to obtain these
data, paleontology can throw no light whatever upon the
primitive Vertebrate or its ancestors, for the Vertebrates
have apparently an antiquity greater than that of the oldest
fossil-bearing rocks; and even if there are in existence fos-
siliferous rocks bearing the remains of the ancestor of Verte-
brates (excluding Amphioxus), we can hardly hope, when
they are found, to obtain any knowledge of the ontogenetic
development or structure of soft parts, and the light which
paleontology throws upon the later history is at present difficult
to use in settling questions of this kind,! so that we are thrown
almost entirely upon embryology for the facts; but the facts
which embryology at present supplies us with are quite inade-
quate to enable us, even approximately, to solve the problem.
1 In making out the phylogeny of organs which have had an early origin,
it seems to me that geology can help us in this way (amongst others).
Those forms which are found in the oldest rocks, and which have existed
as small isolated groups, very little changed apparently in structure, to the
present day, probably retain the same method of development now as
then. By examining the embryology of such living forms we might
expect to find the development of certain organs different to that in other
animals belonging to larger living groups. Turning to the Brachiopoda, a
group of great antiquity, we find a development of the body cavity which
is shared by but few animals, and which @ priori we regard as the most
primitive method of development of that organ known. Now, of the
animals which resemble the Brachiopoda in this respect, Balanoglossus,
Amphioxus, and Sagitta are soft bodied, and so not found as fossils; but
their very isolation at the present day, with recard to their relations to
other groups, suggests that they are survivals of some larger groups, the
other members of which have undergone so much evolution that their
relationship is unrecognisable. The other group, Echinodermata, which
resents this method of development, is found at its greatest development
in Paleozoic rocks, and has not undergone any very marked changes since
that time. It seems to me that, by following this line, some very important
help might be obtained in helping us to decide questions of organ
phylogeny.
WOLFFIAN DUCT AND BODY IN THE CHICK. 453
But still, such as they are, it seems worth while to put them
together, and to discuss the conclusions to which they seem to
point.
Mr. Balfour! has compared the embryonic record to an
ancient manuscript in which many leaves are missing, many
moved out of their proper order, and many spurious ones inter-
polated by later hands. It is the duty of an embryologist to
try to reconstruct the manuscript and see exactly what it contained
when it was first written. In doing this he is aided by the fact that
he has access to many copies of the manuscript, which have
each been used and altered by very different people. He is thus
able, by comparing the different copies, and by studying the
characters, &c., of the people by whom they have been possessed,
‘to arrive at a more correct idea as to what the original was like
than if he had only one copy.
In studying the various embryonic records we have we can
pick out certain features common to all, and which may be
assumed to have had their counterpart in the phylogenetic
history. But the majority of features have been so altered that
it is only possible to arrive at anything like a conclusion by
taking into account the complicated conditions in which the
animals have lived.
Discussion of the preceding Facts.
While the pronephros is characterised by a very similar struc-
ture and development in all the animals in which it occurs, the
mesonephros, though possessing in all animals a fairly similar
adult structure, presents most remarkable differences in develop-
ment in the different groups. While the mesonephros is uni-
versally (few Teleostei excepted) present, the pronephros is only
present in certain forms. Considering first the Ichthyopsida, it
is at once seen that the presence or absence of a pronephros is
correlated with another peculiarity. When the pronephros is
present the egg contains a relatively small amount of food yolk,
and the young undergo a considerable part of their development
after leaving the egg; while, when the pronephros is absent, the
egg contains a very bulky food yolk, and the young undergo
far the greater part of their development within the egg (Hlas-
mobranchii).
Further, again considering the Ichthyopsida, we find that one
method of development of the mesonephros is found in those
animals with a pronephros, while the other method is found
in those animals without a pronephros. Of the two methods of
development of the mesonephros, while one (that found in
} *Comp. Embryology.’
454 ADAM SEDGWICK.
Elasmobranchii) may be considered as in some respects primitive,
the other must be regarded as very much modified.
Whatever may have been the phylogenetic origin of the
Wolffian tubules, the ontogenetic origin, as seen in Amphibia,
Teleostei, Ganoids, Marsipobranchii, cannot possibly be re-
garded as in any way approaching the former. We cannot
suppose that a definite serial organ like the mesonephros de-
veloped in phylogeny as a series of independent cavities in a
mass of mesoblastic cells. At any rate, I think I am justified,
in the present state of our knowledge, in making this statement.
It is completely opposed to our ideas, and can only be accepted
when all other hypothesis as to the origin of the mesonephros in
phylogeny, based on the facts of embryology, have been shown
to ‘be untenable.
The tubules of the mesonephros in Hlasmobranchii, however,
in which group they arise from parts of an organ previously
developed, present a method of development which is not at all
at variance with our @ priori views as to their phylogenetic
origin. From considerations of this kind it seems to me a fair
assumption that the development of the tubules in Hlasmo-
branchs from parts of the body cavity more nearly resembles
the method by which the organ arose in phylogeny than does
that of the Wolffian tubules of the remaining Ichthyopsida.
In Elasmobranchs the Wolffian tubules have a segmental
arrangement; one is found in each segment. In all probability
this also is a primitive condition.
The arrangement of the tubules in the other vertebrata,
although it does not actually afford support to this view, still it
does not disprove it. It is a well-known fact that the segmental
tubes have very rarely a segmental arrangement in the adult or
even in theembryo. But in this connection it must be remembered
that the tendency of development always seems to be to render
that part of the mesonephros, which is going to function in the
adult as an excretory organ, more compact, 7.e. to bring its
constituent parts closer together. I need only refer to the kid-
neys of the Urodele Amphibia. Here the posterior part of the
mesonephros, which is going to function in the adult as kidney,
becomes distinguished by its size and the course of its ducts
from the anterior part, and in the female by its size only from
the anterior part. And Fiurbringer has shown, in Salamandra
maculata, that in correspondence with the increasing size of the
posterior region there is found an increased number of primary
tubules in a segment, as well as of dorsal secondary tubules.}
1 Spengel however asserts, that in the female of those Amphibia he has
investigated, the kidney (mesonephros) contains an uniform number of
WOLFFIAN DUCT AND BODY IN THE CHICK, 455
Spengel has also shown that even in different species of one
genus the number of primary tubules in a segment differs, e.g.
in Spelerpes variegatus there 1s one primary tubule in a segment,
in Spelerpes fuscus there are two.
Further, Firbringer states that in the species investigated by
him the number of primary tubules in a segment increases with
the age of the animal.
“Die Anlagen sind in ihren friheren Entwickelungsstadien
leicht zu scheiden ; spiiter hingegen lagern sie sich so innig an
einander, dass eine Abgrenzung unmoglich wird.”?
Finally, there seems to be a distinct relation between the
closeness of aggregation of the tubules with regard to the body
segments and the number of segments found between the
mouth and the anus.
In the Anourous Amphibia, where there are very few segments
in the adult in this region, we find a very compact and complex
kidney.
In thie Urodeles, in which the number of segments is greater,
the kidney occupies a greater number of segments, and is not
nearly so compact, while in Ceecilia, in which the anus is almost
terminal, very few segments being placed behind (tail undiffer-
entiated), we find that the kidney is segmental, 7. e. one primary
tubule is found for each segment, and it occupies in the adult
as many as sixty segments.”
Turning to the Amniota, we find that in Lacertilia® the
mesonephros has at first a segmental arrangement, one primary
tubule for each segment, and although it has not been shown that
the fully developed mesonephros of lizards has lost this feature,
still there can be little doubt, considering its resemblance to that
of Aves, that it has; while in the case of the chick* the
number of primary tubules in a segment increases with the age
of the embryo.
These three facts, viz.—(1) The variability of the number of
primary tubules in a segment in closely allied forms, (2) the
increased > number in a segment as development proceeds, (3) the
relation between the compactness of the kidney and the number
of segments over which it extends, all point in the same direc-
tion. They seem to indicate that the tubules of the Wolffian
segmental tubules in each segment over its whole area; while in the male,
he finds that they increase in number behind.
1 Loc. cit., p. 19.
2 Spengel.
3 Braun.
4 Self, ‘ Quart. Journ. Mier. Sci.,’ April, 1880.
5 There is no evidence that this is effected by intercalation in the chick
at any rate.
456 ADAM SEDGWICK.
body are capable of shifting their position according to the
wants of the particular species.
We know very well other organs can do this, and I need only
mention the anus placed so near the head in frogs, and so far
off in Ceecilia, and it seems only probable that an important
gland like the kidney should be capable of acquiring a position
and arrangement of its constituent parts different from the posi-
tion of their development, if it is advantageous for the per-
formance of the function of the organ.
The evidence which at the first look appeared so strong
against the primitiveness of the Elasmobranch arrangement of
one primary tubule to each segment proves on examination to
lose a great part of its force.
I now come to a difficulty which apparently at present presents
an insuperable obstacle to a successful solution of the question
under consideration, viz. What was the structure and deve-
lopment of the excretory system of the ancestral Vertebrate ?
Assuming that the development of the Elasmobranch mesone-
phros presents primitive features in the two details already con-
sidered, its development in a third particular can by no means
be assumed to be primitive. The fact that the segmental
duct develops independently of the tubules cannot, in the
present state of our knowledge, be regarded as primitive.
Objections of precisely the same kind as those used in arguing
against the development of the tubules in Amphibia, &c., being
primitive present themselves here.
Any phlyogenetic hypothesis which presents difficulties from
a physiological standpoint must be regarded as very provisional
indeed. The physiological difficulty present in the conception
that in the evolution the mesonephros has arisen by the fusion of
two distinct parts, viz. the duct and tubule, is so great that
until facts are brought forward to show a different origin we
must consent to admit our total ignorance on this point. I
think that the observations recorded in the first part of this
paper on the development of the Avian Wolffian duct and
anterior tubules are of great interest in this relation. Here
we have the Wolffian duct and tubules developing in continuity
in the anterior part of the excretory system, which has been
always admitted to present the most primitive development.
But this point I must again keep for later consideration.
So far, then, the following conclusions have been reached—the
development of the mesonephros of Hlasmobranchii is in part
primitive (tubules), and in part very much modified, while the
development of the mesonephros of Amphibia, Teleostei, &c.,
is in all respects modified.
Turning to the development of the segmental duct, we find
WOLFFIAN DUCT AND BODY IN THE CHICK, 457
ourselves obliged, for precisely similar reasons to those already
given in the cage of the mesonephros, to suppose that that
ontogeny is in this respect more primitive in which the duct
arises as a continuous groove constricted off from the body
cavity than that in which it arises as a solid knob (modified
groove) for only a very small part of its course, and undergoing
the major part of its early growth quite independently of sur-
rounding structure.
In Elasmobranchii that part which develops as a groove
persists as a groove throughout life (abdominal opening of
Miillerian duct).
In Amphibia, &c., that part which develops as a groove
becomes constricted off first in the middle, and then backwards
and forwards, but in front it is constricted in a manner,
according to Fiirbringer not understood, so as to leave the
variable numbers of openings of the pronephros.
However this may be, apparently the openings of the prone-
phros develop as unclosed portions of the anterior end of the
groove from which the duct arose, and they open into a space
placed at the root of the mesentery close to the notochord and
close to the point where in a previous stage the body cavity
communicated with the muscle plates.
In the Amphibian, and apparently in the Teleostean, there is
no marked structure corresponding to the intermediate cell mass
of Elasmobranchii. The muscle-plate cavity is, after its separa-
tion from the general body cavity, only separated from the latter
by a double layer of cells, forming its ventral wall and the wall
of the body cavity ; 2. e. there is no portion of the body cavity
at first continuous, but subsequently divided up by the coming
together of its walls into a series of canals connecting the general
body cavity with the muscle plates.
Now the glomerulus of the pronephros develops in a part of
the body cavity anatomically corresponding to the intermediate
cell mass of Hlasmobranchii, only in Amphibia it does not, in
this region, become divided up into chambers corresponding to
the segments.
With this part of the body cavity, from the somatic walls of
which the original groove arose, the openings of the head-kidney
communicate. The number of these openings corresponds with
the number of segments occupied by the pronephros in all those
animals in which they exceed one, except Myxine; but the
development of the pronephros in Myxine is not at all known,
and its adult structure is, on the whole, obscure.
Turning again to Elasmobranchs, we find that the anterior
knob of the segmental duct arises from the intermediate cell
mass, 7. é. from a part of the body cavity corresponding serially
458 ADAM SEDGWICK.
with that with which in the succeeding segments it later unites
when the young segmental tubes acquire a communication with
the segmental duct.
In Awphibia the segmental duct, when larval life is tolerably
advanced, opens into a Wolffian tubule, which arises from a mass
of cells, the origin of which is obscure, but which apparently
does not appear till after the larva has left the egg. Now the
Wolffian tubule of an Amphibian is homologous with that of an
Elasmobranch ; it is similarly constructed, and opens into the
body cavity at a corresponding point. Hence we are driven to
the conclusion that the cells from which the Wolffian tubule in
an Amphibian arise are homologous with the intermediate cell
mass of an Elasmobranch.
But in Amphibia these cells are not developed where, if
Elasmobranch development is primitive, they should be; and
appear later in a way which gives no clue to their relationship
to the intermediate cell mass in Elasmobranchii.
What is the meaning of this extraordinary method of deve-
lopment ?
In Elasmobranchs the development of the segmental duct is
modified, while the development of the mesonephros is primitive
in its segmental arrangement and origin as a specialised part of
an organ present at an earlier stage.
In Amphibia the development of the segmental duct is more
primitive, but that of the mesonephros very modified, and this
very latter fact always goes hand in hand with the presence of a
pronephros. Turning to the pronephros, it is found to develop
in continuity with the segmental duct. It is found to possess,
with regard to its openings into the body cavity, a segmented
structure. It is also found to possess a structure, the glome-
rulus, resembling extraordinarily closely the glomerulus of an
ordinary Malpighian body of the mesonephros. ‘This glome-
rulus lies in a special part of the body cavity, just as a glome-
rulus of a Malpighian body in the mesonephros of an
Elasmobranch lies in what from its origin may be called a
specialised part of the body cavity; and both these specialised
sections in their anatomical position precisely correspond (see
above, p. 457).
With all these similarities can the inference be avoided that
the head-kidney is descended from the same primitive excretory
system as the mesonephros, which has appeared early in develop-
ment to supply the larva with an excretory organ, and has been
able to retain a more primitive development ? The larva, having
this, has not wanted the hinder part, and in consequence, having
all its energy occupied while within the egg in developing those
organs which it will really require as a larva, it leaves over the
WOLFFIAN DUCT AND BODY IN THE CHICK, 459
development of the organs not so required until after it is
hatched ; and in order that it may not be burdened by useless
organs, the cells from which the tubules after appear and which
should appear, if keeping the phylogenetic order, quite early in
embryonic life, in a way already indicated, are reduced so as
hitherto to have escaped observation.
It is perfectly true that the pronephros does present peculia-
rities of structure not presented by the mesonephros, such as the
unsegmented nature of the glomerulus, and in the fact that the
tube connecting the cavity in which the glomerulus lies with
the segmental duct not being coiled. But in the fundamental
structure, 7.¢. in the possession of a glomerulus placed close to
the main vascular channel (aorta), in the segmental arrangement
of the openings of the segmental duct into the cavity (anatomi-
cally corresponding in both cases) containing the glomerulus,
in the cavity containing the glomerulus being a specialised part
of the body cavity ; in all these points the pronephros and meso-
nephros resemble each other.
Assuming for the moment the truth of this suggestion, we
find the pronephros to present that method of development
which @ priori we are bound to assume would be if it were not
for disturbing causes, the development of the mesonephros,
because it represents the most probable method by which the
mesonephros and its duct can have arisen in phylogeny.
The question now arises, What are the disturbing causes
which in Amphibia have so changed the phylogenetic develop-
ment? The answer has already been given, but I will repeat it
here. It has been brought about by the action of natural selec-
tion on the innumerable larve produced, so that only those ani-
mals reached the adult state which in their prelarval and larval
development conformed to the type of development we have
before us.
Admitting the possibility of both prelarval as well as larvul
development varying at any particular stage, the tendency has
been to produce a dissimilarity in the early structure of the ex-
cretory organs of Hlasmobranchii and Amphibia greater than
that which exists in the adult state, a result entirely m opposition
to what we should expect from the application of that principle
which has been laid down as regulating embryonic development,
viz. that embryos of different animals, starting as fairly similar,
become more and more dissimilar as their development proceeds.
To get any actual proof from embryonic development in favour
of the above hypothesis must, from the nature of the case, be
very difficult. For the very reason of the existence of the pro-
nephros as an anterior part of the excretory system well marked
off from the posterior makes it improbable that anything more
VOL. XXI,—NEW SER. H A
460 _ ADAM SEDGWICK,
than a trace of the hinder part should appear simultaneously in
embryonic development with the anterior part. If the rest of
the mesonephros developed continuously with the duct and
simultaneously with the pronephros, then, on the above hypo-
thesis, we should not be able to distinguish a pronephros from
the hinder part ; and it is opposed to all our ideas of economy to
suppose that a rudiment of the mesonephros should appear at
what phylogenetically would be the proper time, remaining over
as a rudiment in the larva, z.¢. as a useless organ forming
merely a burden until it was wanted.
It seems to me that we can only expect, at the very utmost,
to find a very small trace of the mesonephros in embryonic de-
velopment at what phylogenetically we should consider, on the
above hypothesis, to be the proper moment relative to the
pronephros.
I have been examining the development of the segmental
duct in an Amphibian, the frog, to see if at the time of closure
of the groove of the segmental duct any trace of a discontinuous
closure such as we find in the head-kidney existed. If the
pronephros is merely the anterior part of a segmental organ
of which the mesonephros is the posterior part, and if
phylogeny is in any way repeated in the development of the
pronephros, we should expect to find that the discontinuous (seg-
mented, see above) closure of the pronephros would be repeated
behind, showing some traces at least of the openings of the
segmental duct and of the specialised part of the body cavity
which later forms the Wolffian tubule and contains the glome-
rulus. So far it cannot be said that my search has been from
my point of view successful. ‘To get any evidence of what I was
searching for requires a very complete series of sections in a state
of preservation favorable for observation. The difficulties pre-
sented by the embryonic Amphibia in their early stages to such a
successful result are very great. In the first place they are
very brittle, and comparatively very few of the sections, even if
thick, can be mounted uninjured. Of these, very few, indeed,
can be obtained perfect, and those so obtained are apparently
more difficult to see anything in than the thick ones. The cells
are full of yolk granules which seem to escape and obliterate the
outlines of the cells from the sight.
While my results have not been such as to unable me to speak
with any confidence either one way or the other, yet on the
whole they have convinced me that a re-examination with a new
method of the development of the segmental duct in Amphibia,
&c., would repay the trouble.
In the chick, on the other hand, the anterior part of the seg-
mental duct, for the space of five segments, develops exactly in
WOLIFFIAN DUCT AND BODY IN THE CHICK. 461
the manner of the segmental duct and head-kidney of the
Ichthyopsida. Are the cell cords connecting the duct and peri-
toneal epithelium in these segments rudimentary Wolffian
tubules, or are they rudiments of a head-kidney? In the
absence of a continuous glomerulus opposite them they differ
from the openings of the pronephros. In their development
they resemble the latter. If they are Wolffian tubules they
develop quite differently from all other Wolffian tubules. If
they are rudimentary pronephric funnels, then the chick pos-
sesses a rudiment of a pronephros which resembles exactly
the hinder developing Wolffian tubules.
It seems to me that these structures, under the light of the
above hypothesis, present no difficulty, and I cannot help thinking
that the discovery of their method of development is striking
evidence in its favour. They belong, on that hypothesis, to the
anterior part of the excretory organ, which has retained the
primitive method of development originally characterising the
whole organ. They, in some Avian ancestor, have constituted
the first developed part of the excretory system, which has been
utilised by the larva as its excretory organ. Supposing that
Avian ancestor existed now, we should find that its larva possessed
an organ which we should call pronephros, having a structure
less modified probably from the hinder part of the excretory
system than in the case of the Ichthyopsida, i.e. an organ the
serial homology of which, with the mesonephros, would no more
be disputed than is that of the metanephros with the meso-
nephros.
It may be objected to this view of the anterior part of the
Avian excretory system, that it differs in certain marked features
from the pronephros of other forms. Of these differences the
most important is, perhaps, the fact that there is always found
an interval unoccupied by segmental tubes between it and the
mesonephros, But in Amphibia Salamandra Fiirbringer! dis-
tinctly states that rudiments, as masses of cells, occupying the
same relative position to the segmental duct as do segmental
tubes, are found intervening between the two. If these rudi-
mentary tubules underwent full development there would be no
such gap as that we now find between the pro- and mesonephros
of Amphibia.
But this difficulty is merely part of another difficulty which it
seems to me must exist whatever view be taken of the nature of
the pronephros, namely, why does this organ, so well developed
in the larva and apparently perfectly well performing the func-
tions of an excretory organ, atrophy in the adult? And this
difficulty only seems capable of the unsatisfactory explanation,
1 Loc. cit.
4.62 ADAM SEDGWICK,
that though perfectly well suiting the requirements of the larva,
its position is unsuitable for the satisfactory performance of
its functions in the adult. Balfour has suggested! that the
atrophy of the pronephros is due to its position in that part of
the body cavity which eventually becomes the pericardium ;
and has pointed out, as a confirmation of this view, that it
only persists in the adult of those animals in which it is com-
pletely shut off from the body cavity, e.g. Teleostei.
(The enormous size which the pronephros attains in adult
Teleostei is peculiar, but, coupled with the remarkably feebly
developed mesonephros in the adult, is not astonishing. The
pronephros seems capable of carrying on all the excretory work
in some adult Teleostei, in which the mesonephros is not present.
The absence of the mesonephros in these cases is probably purely
secondary, and, no doubt, traces of it would be found if a close
examination were made. The survival of a larval character into
the adult state is paralleled by the Axolotl’s gills.)
A second feature of difference between this anterior part of
the Avian excretory system and the Amphibian pronephros, is
the absence in the former of a continuous glomerulus. This
may be abortion from disuse, and does not really present a
serious difficulty.
A third feature of difference is that the Avian pronephros
extends over a much greater area than that of the Ichthyopsida,
but when I draw attention to the fact that this difference is
found amongst the various members of the Ichthyopsida them-
selves, | think it can hardly be looked upon as a difficulty. In
Teleostei the head-kidney is distinguished by one peritoneal
opening and a correspondingly short glomerulus. From this we
have all stages to the five peritoneal openings of Petromyzon.
Finally, even if the Avian pronephros did differ in certain
features from the Ichthyopsidan pronephros, this can hardly be
regarded as a serious difficulty.
The pronephros of Teleostei with its Malpighian capsule
containing the isolated glomerulus, and with its one peritoneal
opening, surely differs considerably from the pronephros of the
frog with its three peritoneal openings and its glomerulus lying
free in the body cavity.
Again, without laying too much stress upon it, I point to the .
pronephros of Myxine, which differs still more remarkably from
that of other types.
The difficulty presented by the Elasmobranchii, in which the
tubules, though retaining certain primitive features of develop-
ment, do not develop in continuity with the duct, is very great,
and in the present state of our knowledge no satisfactory ex-
' «Comp. Embryology,’ vol. ii.
WOLFFIAN DUCT AND BODY IN THE CHICK, 463
planation, founded on facts of development, can be given of it.
I will suggest a possible, but entirely rough and hypothetical,
solution on the lines so far followed.
Before the Elasmobranchii produced eggs with the large food
yolk they at present possess, they may have undergone a large
part of their development in the surrounding medium as free
larvee. These larve must have left the egg at a time when
the cavities of the muscle plates were still open to the body
cavity, and when the segmental duct had only just commenced
to be formed in front, and before the development of the vascular
system, and therefore before the glomerulus, the functions of
which were probably carried on by the walls of the body cavity.
The segmental duct was quickly developed from a groove into a
duct, the larve thus precociously developing a recently acquired
adult structure. With this constitution the larva of the ances-
tral Elasmobranch quickly developed the rest of its excretory
system. In consequence of the larva having been hatched at a
very primitive stage, before the muscle plates were separated
from the body cavity, certain primitive characters in the develop-
ment of the segmental tubes were retained. These characters
have been more or less transmitted to the present day, this
having been rendered possible by the acquisition of food yolk
and abolition of the larval state.
However this may be, and it is useless now to make hypo-
theses of this kind, we can only wait till a more close study of
Klasmobranch development has been made to see if any traces
can be found of the disturbing cause which has produced the
modification in the development of the excretory system assumed
on the above hypothesis, and very possibly in the search along
the lines which this hypothesis indicates quite a different view as
to the phylogeny of the vertebrate excretory system may pre-
sent itself.
Before concluding I will briefly state what I think to have
been the structure of the primitive excretory system in the
ancestral Vertebrate.
There was a duct occupying the position of the segmental
duct, i.e. at the dorsal outer angle of the body cavity, at the
point where the latter becomes separated from the cavities of
the muscle plates. This duct opened in each segment into the
dorsal part of the body cavity. On the inner wall of the latter
projected on each side a vascular ridge formed by the aorta.
Behind, the segmental duct opened into the cloaca.
As differentiation proceeded the vascular aortic ridge became
more especially developed opposite each opening of the segmental
duct, and parts of each of these enlargements became succes-
sively enclosed in a special part of the body cavity, giving rise
464. ’ ADAM SEDGWICK.
to the commencement of the secondary glomeruli. With this
division of the glomerulus segmentally, and of each segment of
it into further secondary glomeruli, each lying in a specialised
part of the body cavity, the openings of the segmental duct
began to fold and divide, incompletely at first, into special open-
ings, one for each secondary glomerulus. Finally, this division
was completed, and the segmental duct communicated by a
number of openings in each segment with specialised parts of
the body cavity containing a portion of the original aortic ridge.
The specialised parts containing these glomeruli being still open
to the body cavity, and the glomeruli being still all distinctly
attached by a common stalk to the walls of the body cavity, and
the intermediate parts of the original continuous ridge having
completely vanished, now the capsules enclosing the glomeruli
became more and more completely marked off from the body
cavity. The openings putting them in communication with the
segmental duct elongated into tubules which became coiled, and
the glomeruli themselves gained a greater independence of each
other by a development of intermediate tissue.
A trace of the original state of things has descended to the
present time in the pronephros, with its continuous glomerulus
opposite the opening of the segmental duct, and placed in a
specialised part of the body cavity. Differences in structure
from the supposed primitive state of things have of course arisen,
in consequence of the specialisation of the pronephros as the
larval excretory organ.
In the same way a trace of the division of the primary
glomeruli into primary, secondary, &c., glomeruli, is left
in the curious development of the external glomeruli of the
anterior part of the Avian mesonephros. Only in this case no
cause can apparently be given for the retention of this primitive
feature of development.
An examination of an early stage in the development of the
Avian Wolffian tubules, when the primary and secondary
tubules are both fairly well established, but not very compli-
cated in structure, points very distinctly to the fact that the
glomeruli of the two tubules are parts of one primitive glome-
rulus. ‘They appear to be continuous, and while one looks
ventrally, .e. the so-called primary glomerulus, the other looks
dorsally. A glance at the accompanying woodcut will make
this clear.
If this drawing of a section through the Wolffian body of a
chick in a part with primary and secondary tubules, be compared
with fig. 24, which is from the anterior part of the same chick
where there are no secondary tubules, it will be seen that the
WOLFFIAN DUCT AND BODY IN THE CHICK. 465
step between them is not great.' It is merely necessary to
suppose the division of the glomerulus (in fig. 24) into two
parts, and a simultaneous development of certain folds from the
Wolffian duct to form the tubules, and the original single
tubule would have been transformed into a ventral primary
and a dorsal secondary tubule.
Further, as I have pointed out in another paper, the secon-
dary tubule always arises in close proximity, apparently from
a blastema continuous with a part of that from which the
primary tubule arose.
A modification of development is to be expected, because in
those animals in which the mesonephros develops after hatching,
it clearly comes gradually into use. The whole is not wanted
at once, but with the increasing size of the larva, more tubules
are wanted. ‘The first developed (primary) in Salamandra
acquire a structure with which they can apparently perform
their function when there is hardly a trace of the secondary
tubules (Furbringer, loc. cit., fig. 26).
' It will be observed that in this figure the tubule connecting the
Wolffian duct and capsule is hardly developed. In all probability, this was
on the analogy of the pronephros, the primitive state of things, the tubule,
being a secondary differention of the duct near each glomerulus.
?* Quart. Journ, Mier. Sci.,’ April, 1880.
466 ADAM SEDGWICK.
A cause of abbreviation is so clear in this case that I need not
waste time in stating it.
But the whole details of the development of the secondary,
&c., dorsal tubules needs reworking, for, with the exception of
the observation of Mr. Balfour’s for Elasmobranchs, we have no
real knowledge of their exact method of development. The result
of such an investigation cannot but be exceedingly interesting
from a phylogenetic standpoint.
I cannot help thinking, as before stated, that the development
of the external glomeruli in the chick may have some interest in
this relation.
The modification of the mesonephros of the Amniota is, on
the above hypothesis, due to the fact that some Avian ancestor
possessed a larva in which the anterior part of the excretory
system was early developed, the development of the hinder part
being deferred, and consequently modified, just as we see to be
the case now in the Ichthyopsida.
The stiJl greater modification und retardation of the develop-
ment of the metanephros or true kidney of the Amniota, and
the great size which the Wolffian body reaches in the embryo,
are striking facts which demand consideration in any discussion
of the Vertebrate excretory system.
In my paper on the “ Development of the Kidney” I have stated
my views on the relation of the Amniote kidney to the mesone-
phros. But one point in that paper is left untouched.
Why does the kidney appear so late? and also why does the
Wolffian body become so large and complex—so much larger
than the small-sized chicks, in which it is fully developed, can
need ?
And, further, why should this organ, apparently so well
adapted to serve as the excretory organ of the adult chick,
atrophy ?
It may be said, in answer to the latter question, that only
those tubules of the mesonephros which open into the cloaca
independently of the Wolffian duct can function in the adult, as
those which have not so changed their course would interfere
with the function which the Wolffian duct later acquires—the
carriage of semen.
It seems to me that the only answer which can be given to
the first of these questions is this:
The kidney is thrown back in development for the same
reason that the mesonephros of the Amphibia is, viz. because
the ancestor of the chick underwent part of its development out
of the egg, at which stage of development the testis, not being
developed, did not interfere with the excretory functions of the
Wolffian tubules, or vice versd. The large size of the mesone-
WOLFFIAN DUCT AND BUDY IN THE CHICK, 467
phros, then, is to be explained on the supposition that the larva
of the chick’s ancestor used it for a considerable period of its
early life as an excretory organ, so that it may be said that the
pronephros holds the same general relation to the mesonephros
in the Ichthyopsida as does the mesonephros to the metane-
phros in the Amniota.
I do not mean to affirm that the above explanation of the
lateness of the development of the metanephros is absolutely
valid, for I think that a careful consideration of the develop-
ment of the hind part of the mesonephros in Amphibia and Elas-
mobranchii might necessitate a slightly different explanation.
But an explanation of that kind must be sought to explain the
remarkably late development in the chick of an organ which
phylogenetically must be assumed to have had an origin simul-
taneous with that of the mesonephros.
With regard to the relation which the testes enters into-with
the mesonephros, it is interesting to notice the modified develop-
ment which always characterises this connection.
Here it can be definitely affirmed that the lateness and conse-
quent modification of the process is due to the fact that the
apparatus has not been required in the larve of the Ichthyopsida
and of the Amniote ancestors, and consequently has been put off
and modified in development. The explanation is exactly similar to
that given for the modification in development of the Amphibian
mesonephros, except that here we are supposed to be able to
assert with greater reason that the putting off and consequent
modification is due to the fact that the connection between the
testes and mesonephros was not wanted sooner, and so was not
developed. .
Summary of the Hypothesis and main Arguments used.
The whole of the Vertebrate excretory system, including pro-
nephros, mesonephros, and metanephros, are derived from a
primitive organ possessed by the ancestral Vertebrate. This
organ had a segmental character, and consisted of a duct, the
segmental duct opening in every segment into the body cavity,
close to a continuous structure, known now as the glomerulus,
which was placed close to the main vascular channels and acted
as an excretory organ.
The anterior end of this organ was used by the larva, and
developing more or less with regard to other structures at the
normal time, retained many primitive features of development
originally characterising the whole organ, and is known to us as
the pronephros. The posterior part of the organ had its develop-
ment delayed with regard to other structures, particularly those
in connection with which it primitively developed ; the develop-
468 ADAM SEDGWICK.
ment was consequently modified. This part is known to us as
the mesonephros.
The same hypothesis was applied to account for the retarda-
tion and modification of the development of the metanephros
with regard to the mesonephros in the Amniota.
The main facts in favour of the hypothesis are—
1. The development of the segmental tubes in Hlasmobranchii
and of the pronephros and segmental duct of the Ichthyopsida as
parts of the body cavity.
2. The obvious modification in development of the meso-
nephros, accompanying also the presence of a pronephros in
most of the Ichthyopsida.
3; The resemblance in structure between the pronephros and
mesonephros, particular stress being laid on the fact that the
glomerulus im both glands is developed in anatomically corre-
sponding, i.e. homologous, parts of the body cavity
I may point out before leaving the subject that other views con-
cerning thenature of the pronephros have been expressed by Gegen-
baur, Furbringer;! and Balfour.2. The two former authors look
upon the pronephros as having an antiquity greater than that of
Vertebrates, greater even than that of the segmented ancestors
of Vertebrates. They regard it as being descended from the
primitive excretory system possessed by the unsegmented
ancestor, which has been retained in such forms as Turbellaria
and Rotifera, the segmented posterior part having been added
when the segmented state was reached.
Miillerian Duct.
Balfour’s views as to the phylogeny of the Miillerian duct
and its homology throughout the Vertebrata are well known.
He supposes it is one or, in the chick, more of the head-kidney
openings which have become modified for generative purposes.
I still adhere to the view expressed in the paper on the
“ Rudimentary Head-Kidney of the Chick” as to the meaning
of the peculiar structures at the anterior end of the Millerian
duct, and I think that there are grounds, which it is not necessary
to enter into here, for supposing that the abdominal opening or
openings of the Miillerian duct have been derived from the
anterior part of the excretory system after its modification to
form the pronephros. But I quite admit that a fuller know-
ledge of the early development of the Hlasmobranch segmental
duct may necessitate an alteration in this view.
1 Loe. cit.
2 Balfour looks upon it as the most primitive part of the excretory
system which has been retained by the larva, as so many ancestral organs
are, long after they have been lost by the adult. ‘Comparative Embryo-
logy,’ vol. il.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 469
OxssERvations om the CrantaL Nerves of Scyturum. By A.
Mitnes Marsnatt, M.A., D.Sc., Professor of Zoology in
Owens College; and W. Batpwin Spencer, of Owens
College. (With Plate XXVIT.)
Part I. The Preauditory Nerves.
Tue investigations recorded here were undertaken in the first
instance for the purpose of controlling certain. determinations
published by one of us in a previous number of this journai!
concerning the cranial nerves of Hlasmobranchs. To this end
we have carefully re-examined the specimens upon the investiga-
tion of which the former account was based, and have, in addi-
tion, made a large number of new preparations, illustrating more
especially the later stages of development—stages m to Q of
Balfour’s nomenclature.”
During the course of our work so many altogether new and
unexpected points were brought to light, that we soon found it
necessary to widen considerably the scope and limits of our in-
vestigations, and have finally been led to attempt a complete
account of the development of the cranial nerves from stage K to
the adult form, and to endeavour in this way to connect together
directly the accounts previously given of the early stages® with
the descriptions of the nerves of adult Elasmobranchs published
by Stannius,* Gegenbaur,’ and other anatomists.®
Owing to defective supply of materials, our observations on
the stages earlier than kK are too fragmentary to be reliable; this
we greatly regret, inasmuch as many features in the early stages
are of extreme importance, and would well repay thorough in-
vestigation. |
In the present paper we propose to confine ourselves to the
consideration of the preauditory nerves, reserving the postaudi-
tory, which preseut many features of peculiar interest, for a
future occasion.
' Marshall, “On the Head Cavities and Associated Nerves of Elasmo-
branchs,” ‘Quart. Journ. Micr. Sci.,’ Jan., 1881, pp. 71 seg. Future
references will be to this paper unless otherwise specified.
5 Elasmobranch fishes, pp. 79 and 80.
3 Balfour, op. cit. Marshall, loc. cit.
* Stannius, ‘Das peripherische Nervensystem der Fische,’ Rostock,
1849,
° Gegenbaur, “Die Kopfnerven von Hexanchus,” ‘Jenaische Zeit-
sehrift,’ Bd. vi.
6 Hsp. Jackson and Clarke, “The Cranial Nerves of Zehinorhinus
spinosus,” * Journal of Anatomy,” vol. x.
470 PROF. MILNES MARSHALL AND W, B. SPENCER,
Our investigations have been conducted almost exclusively by
means of sections of hardened embryos of Scy//iwm, and, as on
former occasions, we have found a mixture of chromic and osmic
acids superior to any other hardening agent. For the specimens
from which our best preparations have been made we are indebted
to the courtesy of the managers of the Southport Aquarium ; our
best thanks are also due to Mr. A. J. Moss, of Owens College,
for his gift of a fine specimen of J/ustelus, as well as for valuable
assistance in connection with the literature of our subject.
The Third (Oculomotor) Nerve.— We do not propose to deal in
the present paper with either the olfactory or optic nerves, inas-
much as the former has been already fully described,! while con-
cerning the latter we have nothing new to communicate; we
therefore commence with the third or oculomotor nerve.
Concerning the development of this nerve we have very little
to add to the account given in the paper already referred to.?
At stage L it arises from the base of the mid brain, not far from
the mid ventral line, by a large posterior ganglionic root and by
several smaller anterior ones clearly distinguished from the
former by possessing no ganglion cells. The nerve itself runs
backwards as a long slender stem to the interval between the
first and second head cavities (fig. 11 0., 111), where it expands
into a ganglionic swelling (fig. 11, 0. c.g.) wedged in between
the tops of the two cavities. From this ganglion the two
main branches of the third arise; of these the upper one (fig.
15, m1 4), at a rather later stage, supplies the rectus superior
and rectus imternus muscles, whilst the lower one (fig. 15,
1m ¢) runs down behind the rectus inferior, and ends in the
obliquus inferior muscle (fig. 15,0.2.). Atstage K, at which our
observations commence, the third nerve has the same point of origin
and the same relation to the head cavities; it differs from the
condition described above chiefly in not possessing anterior
non-ganglionic roots, and in not having its terminal branches
fully developed. At stages later than n the nerve seems to arise
from the base of the mid brain by a single large ganglionic root,
no smaller non-ganglionic ones being visible (fig. 14, mr),
though at stage n itself they are very prominent (fig. 13, 111).
Besides the branches of the third nerve, mentioned above,
there are two others in direct connection with the ganglion c.g. :
of these the first, at stage u (fig. 11 0., NV. ¢.), is a short nerve,
which lies along the top of the second head cavity and serves to
' Marshall, “Morphology of Vertebrate Olfactory Organ,” * Quart.
Journ. Micr. Sci.,’? July, 1879, pp. 300 seg.
2 Marshall, loc. cit., pp. 78 seq.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 471
connect directly the ganglion c.g. of the third nerve with the
Gasserian ganglion at the root of the fifth.
The second (figs. 10, 11, and 12, x) passes straight forward
from the ganglion ¢c.g., running through the walls of the first head
cavity under the rectus superior and rectus internus, and through
the substance of the sclerotic on the inner surface of the eye-
ball. Passing out from the orbit, immediately above the odliquus
inferior, it still pursues its course straight forward, but becomes
more superficial. In the earlier stages it crosses the root of the
olfactory nerve, with which it lies in very close contact: in
the later stages (figs. 12 and 15, nN) it is, rather more dorsally
situated, and then crosses the ophthalmic branches of the fifth and
seventh nerves at a considerable angle (fig. 12, ), and ends in
the skin at the extreme fore part of the head. After careful and
repeated examination we have failed to detect any branch given
off from the nerve at any point of its length.
At stage K all the above-mentioned branches of the third
nerve are developed, except the upper branch, to the rectus
superior and rectus internus, which we have failed to detect:
the ganglion c.g. is very conspicuous, and the nerves NV.c. and WV.
have the same structure and connections as at stage Nn, the
latter of the two stretching forward to the extreme anterior
part of the head, in the skin of which it ends.
In the later stages the modifications which the third nerve
undergoes are merely ones of detail, all the principal branches of
the nerve being already established, and maintaining their relations
practically unaltered in the adult. The most important changes
concern the ganglion c.g. ; this, which at stages K and L isa
large prominent swelling (fig. 10, ey.), in the later stages
becomes far less conspicuous, and the ganglionic cells, instead
of being concentrated at one spot, occur in small scattered
patches at different parts of the nerve. This change is seen
commencing at stage N (fig. 11, ¢.g.), where the ganglion has
divided into two main portions, one part retaining its original
position, whilst the other becomes connected with the nerve J.
at some little distance from the third nerve; at stage o-p
(figs. 14 and 15) ganglion cells appear to be constantly present
at two well-marked points in the course of the third, (1) where
the nerve JV. is given off, and (2) immediately above the rectus
superior.
At stages K and t (fig. 10) the angle between the nerves N.c.
and J. is very considerable, and this increases in the later stages
so much that at stage N (fig. 11) the two nerves are almost at right
angles to one another; at stages later than this the nerve WV.
is much more difficult to define, whilst owing to the close
4.72 PROF. MILNES MARSHALL AND W. B. SPENCER,
proximity of the third to the fifth nerve it is only with extreme
difficulty that the nerve JV. c. can be distinguished at all.
We find, therefore, that the main stem and the branches 111d
and ie of stage n become directly the neryes which have the
same course and relations in the adult. The ganglion e.g. be-
comes the ciliary ganglion of the adult.1 The nerves WV. and
N.c. become directly continuous with one another, and together
form the nerve known as the Ramus ophthalmicus profundus.
The discussion of the morphological import of these two very
remarkable nerves we postpone till after the description of the
fifth and seventh nerves. .
The Fourth (Pathetic) Nerve.—Concerning the development
of the fourth nerve no description has yet appeared, and though
our observations do not yet enable us to give a complete account,
still, so far as they go, they are of so definite a character that we
think it» well to record-them here rather than wait for the possi-
bility of completing them at some future time.
The condition of the fourth nerve at stage N is well shown in
figures 1] and 13, of which the former shows the greater part
of its course, and the latter its root of origin. The nerve arises
(fig. 13, tv) from the: dorsal surface of the extreme hinder
border of the mid-brain, so far back indeed that very careful
examination is necessary to determine. whether its origin is
really from mid and not from hind-brain. | The roots of the two
nerves are in close contact on the dorsal surface of the brain.
From its root the nerve runs at first almost directly outwards,
following the curvature of the brain, until it comes to lie a very
short distance below the surface; it then runs backwards and
downwards as a long, straight, and very slender nerve
(fig. 11, 1v), which very commonly branches early in its
course, and: terminates in the odliquus superior muscle. Just
before reaching the muscle (fig. 11) the fourth nerve crosses
the ophthalmic branches of the fifth and seventh nerves at right
angles, lying at a slightly deeper level than these nerves. It
also divides into a number of branches, of which one or more
appear to become connected with similar branches from the
ophthalmic branch of the fifth, the remainder entering the obliquus
superior, whilst in the later stages (fig. 16) the main nerve is
seen to come into very close contact with the two ophthalmic
branches themselves of the fifth and seventh nerves.
It will be seen from the above description that the fourth
nerve has by stage N acquired its adult relations and distribution,
and at stages o-p (fig. 15) and Q (fig. 16), where it is shown in
1 Marshall, loc. cit., p. 87, and Schwalbe, “ Das Ganglion Oculomotorii,”
‘Jen. Zeit.,’ Bd. xiii.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 473
transverse section, it is still the same. In the adult its course,
like that of the other nerves, becomes altered owing to the
varying rates of growth of the brain, the skull, and the face ;
the rapid growth of the skull relatively to that of the brain causing
the fourth nerve to run some distance forward within the brain
case before passing out, when, as before stated, it runs imme-
diately beneath and in very close contact with the ophthalmic
branches of the fifth and seventh nerve.
In attempting to trace the fourth nerve in stages earlier than
nw we have met with considerable difficulties, and have hitherto
obtained only a moderate amount of success. At m the relations
are the same as at N, the sole difference being that the nerve is
more slender than at the later stage. At stage L, though we have
examined a very considerable number of specimens in excellent
histological preservation, we have as yet recognised the fourth
nerve in one specimen only, and even in that one not with abso-
lute certainty. In the specimen in question the nerve has the
same position and relations as at N, but is very much more
slender, so thin, in fact, as to be almost unrecognisable. arlier
than 1 we have failed, after the most careful search, to find any
trace of the nerve. ©
Though our observations are imperfect they yet seem to point
to certain conclusions of importance touching the morphology of
this important nerve. In the first place the fourth nerve is the
only one in the body which, in the adult, arises from the dorsal
surface of the brain ; it is, therefore, of great importance to notice
that from the very earliest stage at which we have seen it the
point of origin is that of the adult nerve.! Inasmuch as the ma-
jority of the cranial nerves, as well as the dorsal roots of the
spinal nerves, arise af first from the dorsal surface of the brain or
spinal cord, it seems natural to suggest that the fourth nerve
differs from all the rest, not in its mode of origin, but in the fact
that, whilst all the other nerves shift their attachment to a greater
or less extent, it alone preserves the primitive position of its roots
of origin, This shifting of the roots is, in part,’ due to the
rapid growth of the dorsal part of the brain forcing the roots of
the two sides from each other; and it becomes of interest to
notice that the fourth nerve arises from a portion of the brain
where this rapid growth of the roof does not occur, and where;
consequently, one cause of the change in the other nerves is
absent.
The fact that the direction of the fourth nerve is at first at
right angles, or nearly so, to the axis of the part of the head
1 Balfour, ‘ Elasmobranch Fishes,’ pp. 156 and 191.
° We say “in part,” because it will be shown further on in this paper
that another process contributes greatly to this shifting.
A474. PROF. MILNES MARSHALL AND W. B. SPENCE,
from which it arises is of importance, as showing that the fourth
nerve comes under the category of segmental nerves ;' and inas-
much as there is no room as regards visceral arches and clefts for
a segmental nerve between the third and fifth the fourth would
probably be rightly viewed as a separated branch of the third—
the only other nerve arising from the mid brain.
On the other hand, certain other facts in connection with the
fourth nerve cannot be explained so easily. Thus, segmental
nerves not only arise from the neural crest ; they also arise early,
are from the first large, and have ganglia at or near their roots.
Now, so far as our observations go, the fourth nerve, though it
may possibly arise from the neural crest, would not appear to arise
early, and certainly is not at first a large nerve, being of much
greater size at stage o-p (fig. 15) than at stage n (fig. 11) ; whilst
at stage L, in the single specimen in whick it has been detected,
it is a nerve of extreme slenderness; moreover, at no part of its
length have ganglion cells been found—an important point of
difference from segmental nerves.
Another curious feature concerning the fourth nerve is that,
in our embryos, it appears almost constantly to divide close to
its root into two or even more branches, as is well shown in fig.
11, 1v. These again subdivide near their terminations (figs.
11 and 15), but a// the branches, whether primary or secondary,
are distributed to the superior oblique muscles, with the possible
exception of a few of the smaller ones, which appear to join the
ophthalmic branch of the fifth. We would suggest that this
branching may possibly be an indication of the fourth nerve
having previously had a more extended distribution than its
present very limited one.
On the whole, our observations lead us to believe that the
fourth nerve is to be regarded as a separated part of that seg-
mental nerve of which the third nerve forms the main portion.
A further suggestion concerning the fourth nerve will be made
after the seventh nerve has been considered.
The Fifth (Trigeminal) Nerve.— We propose to consider sepa-
rately the roots and the branches.
a. The roots of origin.—The earliest stage in the development
of the fifth nerve that we propose to treat of in the present paper
is that represented in fig. 1, taken from a transverse section
through the hind brain of an embryo at a stage intermediate
between 1 and kK, the plane of section passing on the left side
through the roots of the trigeminal (v).
As shown in the figure, the roof of the hind brain is very
1 Marshall, ‘“ Morphology of Olf. Organ,” p. 318, ‘Quart. Journ.
Mier. Sci.,’ July, 1879.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM, 475
thin, and passes rather abruptly into the much thickened sides.
To the top of the thickened portion the fifth nerve is attached
by a long slender root (fig. 1,v a). This root passes down
alongside the brain, but not in actual connection with it, widen-
ing considerably as it does so. Its inner border follows the
curvature of the brain until reaching a point about half way
down the sides of the neural canal ; it then turns suddenly out-
wards, leaving the brain altogether, and forming, as it does so,
a very conspicuous blunt projection (fig. 1, v3), which is in
rather closer proximity to the brain than is the part of the nerve
immediately above it. The trunk of the nerve then passes out-
wards and downwards, lying just beneath the superficial epiblast,
between it and the outer wall of the second or mandibular head
cavity (fig. 1, 2). The whole of the nerve, including its root,
consist of closely-packed spherical or polygonal cells, which, like
all nerve cells in the early stages, stain very deeply with osmic
acid, and differ materially in appearance from the much less
closely arranged mesoblast cells.
By stage k the root of the fifth nerve has undergone very
remarkable changes; as shown in fig. 4, the dorsal attachment
(fig. 1, va) to the top of the thickened side of the brain has
disappeared completely, and the nerve is now attached to the
brain at a point about half way down the side (fig. 3, v (3), 7. e.
at a point exactly corresponding to the conspicuous projection
(fig. 1, v 8) already described at the earlier stage. Immediately
beyond the root of origin the nerve enlarges suddenly, and pre-
sents a distinct dorsal projection at the base of the secondary root
of attachment. Although hitherto we have not secondary in
following all the intermediate stages, and have not yet obtained
satisfactory preparations of the stages earlier than that drawn in
fig. 1, yet we feel justified in putting forward the following ex-
planation of the appearances we have just described, relying
for our justification partly upon the description given by
Balfour, and still more on our own observations on the develop-
ment of the roots of the seventh nerve, which will be described
immediately.
Balfour has described and figured the fifth nerve as arising
at “stage G, near the anterior end of the hind brain, as an
outgrowth from the extreme dorsal summit of the brain, in
identically the same way as the dorsal root of a spinal nerve.’”!
He has further described? how, by the growth of the
roof of the brain, the nerves of the two sides, which at first,
are in contact dorsally, shift their position and become widely
separate. His descriptions and our own somewhat fragmentary
' Op. cit,, p. 191, and Pl. XTV, fig, 3.
2 Op. cit., p. 196,
VOL, XXI,—-NEW SER. ) 11
476 PROF, MILNES MARSHALL AND W. B. SPENCER,
observations on these stages, when considered in connection
with our much more complete series of observations on the
seventh nerve, leave no room for doubt that the root of origin
(v a) shown in fig. 1 is the primary root, the one which at
Stage G was situated at the top of the brain, and which has
acquired its present position merely in consequence of the rapid
growth of the roof of the brain pushing its two lateral halves
apart, and so separating the roots of the nerves.
Concerning the root of attachment (V (6) shown at stage x in
fig. 3 there is more room for dispute. Balfour appears to hold? that
this further change in position is due to the same cause as the
former one, 2. e. to growth of the roof of the brain ; but this ex-
planation, while it would fully account for the first change, would
im no way explain such a shifting of the root down the thickened
sides of the brain, as is clearly seen to have occurred on com-
paring fig. 3 with fig. 1. We believe that what really happens
is that about the commencement of stage K the nerve acquires a
new and secondary connection with the brain at the point (v (3)
opposite the projection already noticed, that the primary attach-
ment (v a) is lost, and that the part of the nerve left above the
secondary root rapidly diminishes and ultimately disappears
altogether, the slight dorsal projection already noticed in fig. 3
being the last rudiment of it. As our arguments in support of
this view depend almost entirely on our own observations on the
development of the roots of the seventh nerve, we postpone
further consideration of the point till a later portion of this
aper.
Tt the commencemént of stage x then, the fifth nerve arises
about half way up the sides of the hind brain by a single large
root in which ganglion cells are abundant, and opposite to which
there is a well-marked external bulging of the walls of the
brain ;? beyond this root the nerve expands suddenly into a very
arge ganglionic swelling, the future Gasserian ganglion.
Before the close of stage K additional roots appear; a long,
slender process runs forward from the anterior-superior angle of
the Gasserian ganglion, and becomes connected with the brain
some distance in front of the main root; in addition to which
one, two, or more roots of a similar kind appear in intermediate
situations.
These anterior roots of the fifth nerve are well shown at
the next stage (L) in fig. 10, v y, which shows that the fifth nerve
at this time arises from the brain by three distinct roots, of
which the posterior one is much the largest, and is the ganglionic
root (v (3) of fig. 3, while the two anterior slender non-
1 Op. cit., p. 196. °
Marshall, loc. cit., p. 84.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM, 477
ganglionic roots are the new ones. We have studied these roots
very carefully, but have been unable to determine with certainty
whether they are outgrowths from the brain to meet the gan-
glion, or from the ganglion towards the brain ;. our observations,
however, though inconclusive, tend very strongly towards the
latter of the two alternatives. It has also occurred to us that
these new roots may possibly be the original primary root of
origin (v a, fig. 1), which, after losing its original attachment,
has acquired a new one lower down; however, though the dates
of the disappearance of v a and appearance of v y agree fairly
well with this hypothesis, we have yet no actual observations
in its favour, and do not wish to lay stress upon it.
These anterior roots which, during stage L, may be three or
more in number, appear in the later stages to be very constantly
reduced to two, one of which is the most anterior of the original
roots while the other appears to be formed by the fusion of the
intermediate ones. ‘This condition at stage N is well shown in
fig. ll, vy. At a stage between o and P (fig. 14, v y) they
are rather less conspicuous owing to the interval between them
and the secondary root (v (3) being filled up by dense tissue.
They are clearly recognisable in the adult, and form, as will be
noticed more fully further on, the first or anterior root of the
fifth nerve of zootomists.
B. The branches of the fifth nerve-—The Gasserian ganglion
is, from its first appearance, wedged in between the dorsal ends of
the second and third head cavities in the same manner as is the
ciliary ganglion between the first and second (fig. 11). From the
Gasserian ganglion, at stage K, two nerves arise; of these, one,
which runs straight down between the second and third head
cavities, and then along the anterior border of the mandibular
arch in front of the ventral portion of the cavity in the latter,
is the mandibular branch, and from this, a considerable distance
below the ganglion, a small anterior branch—the maxillary
nerve—is given off. The second branch from the Gasserian
ganglion arises from its anterior inferior angle, runs along the
top of the first head cavity and joins the ciliary ganglion ; it is
the communicating branch between the fifth and third nerves
already mentioned, and forms the proximal part of the ramus
ophthalmicus profundus of zootomists.
At stage La slender branch arises from the anterior superior
angle of the Gasserian ganglion; this is the ophthalmic branch
of the fifth (fig. 10, v a) which runs forward through the orbit
dorsad of all the eye muscles, giving off branches to the neigh-
bouring parts in its course and terminating in the skin of the
fore part of the head. One other nerve in connection with the
fifth remains to be noticed: this is the connecting branch
478 PROF. MILNES MARSHALL AND W. B. SPENCER.
(V.c’., fig. 10) between the fifth and seventh nerves: this is
present at x, at which stage as well as at L, it forms a very
stout, though short nerve, running forward and downwards from
the seventh nerve, over the top of the third head cavity, to join
the lower part of the Gasserian ganglion.
The branches of the fifth nerve at stage N are well seen in
figs. 11 and 12 which have been constructed so that each of
them may show the whole course and distribution of certain nerves ;
the outlines of the figures were drawn, with the camera, from
individual sections and the branches of the several nerves care-
fully filled in, again by the aid of the camera, from other sections
of the same series. In this way sucha view of the nerve
is obtained as might be got from a transparent embryo in which
the nerves alone stood out as opaque objects. To prevent con-
fusion, from the overlapping of different nerves, two figures
have been given of which the first (fig. 11) shows the roots of
the fifth and seventh, the connections of these with one another
and with the third nerve, the branches of the latter and of the
fifth, the fourth nerve, and some of the branches of the seventh ;
in the second (fig. 12) the remaining branches of the seventh,
with certain of the glossopharyngeal, are shown, and in addition
to these, the whole course of the ophthalmics.
The branches of the fifth nerve are seen to be the following :
1. The ophthalmic branch, (v a) which arises by a slightly
ganglionic root, runs forward over the odliquus superior (o. 8.),
crossing, as it does so, the fourth nerve at right angles and
giving off branches, some of which appear to be connected with
the fourth.
2. The communicating branch (V.c.) between the Gasserian and
ciliary ganglia, the position and relations of which nerve are
sufficiently well shown in the figure. We reserve the discussion
of this branch, merely noticing here that, though we describe it
with the fifth nerve, it appears to belong to the third quite as
much as to the latter.
3. The main stem of the fifth, ranning down behind the first
head cavity (1) and the rectus externus, receiving the communi-
cating branch (J.c.’) from the seventh, and after passing down-
wards and forwards for some distance, dividing into two
branches, (a) an anterior or maxillary nerve (v4) which again
gives off numerous branches to the skin of the upper jaw, and
(6) a posterior or mandibular (v ce) which runs backwards and
downwards, lying in close contact with the outer wall of the
lower part of the mandibular head cavity (2), and supplying it
with branches. The distribution of ganglion cells is sufficiently
shown in the figure ; there is a small ganglion at the base of the
ophthalmic nerve, and the ganglion cells of the main stem
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 479
extend some little distance beyond the point of junction with the
communicating branch from the seventh.
In figs. 14 and 15 some of these branches (va, v4, vc)
are seen at a stage between o and rp: except that the roots of
v and vir are much more closely approximated, there is no
difference of importance between this stage and the earlier one
which we have more fully described. We have traced all these
nerves up to what is practically the adult condition, and have
identified them with the branches bearing the same names in
the adult. Our observations show that in the fifth, as in the
third nerve, all the main branches of the adult nerve are fully
established by stage L, and that the after changes are comparatively
unimportant.
The Seventh, or Facial Nerve.
A. The roots of origin.—Fig. 2 represents a transverse section
through the roots of origin of the seventh nerve of an embryo
between stages 1 and k, the same, in fact, of which fig. 1 repre-
sents the roots of the fifth nerve. The two nerves (vit) are
seen to arise from the extreme dorsal summit of the hind brain,
the roots of origin of the two nerves (vita) being continuous
with one another across the top of the brain. It will also be
noticed, as contrasted with figure 1, that the two sides of the
hind brain are close together, both above and below, and that
the cavity of the hind brain is a mere vertical slit; that, in fact,
the growth of the roof of the brain, which we have seen is the
first cause of the separation of the roots of the fifth, has not yet
commenced in the part of the brain from which the seventh
nerves arise. ‘The section further shows that the nerve on either
side extends down as a somewhat club-shaped mass of compactly
arranged polygonal cells lying between the external epiblast and
the neural canal, but distinct from both, its ventral end having a
tendency to pass to the outer side of the third head cavity (fig.
2, %), just as the fifth nerve passed to the outer side of the
second cavity (fig. 1, °).
The next stage is represented in fig. 3, a section through the
hind brain and roots of the seventh nerve of an embryo of stage
K, of the same age, though not from the same specimen as fig.
4. The figure shows that very important changes have occurred;
the roof of the hind brain has grown rapidly and considerably,
so as to separate widely the two primary roots of the seventh
nerves (vila). On the right side only this dorsal primary root
is seen, but on the left side a considerable portion of the nerve
is shown, and it is seen that, in addition to the primary root
(viI a), which is still present, the nerve has acquired a new or
secondary root (vii 8), about half way down the sides of the
brain. Both roots of attachment are perfectly clear and unmis-
480 PROF, MILNES MARSHALL AND W. B. SPENCER.
takable, while between them the nerve and brain are quite dis-
tinct from one another, and separated by an appreciable interval.
If tig. 3, showing the condition of the root of the seventh
nerve at stage K, be compared with fig. 1, showing the root of
the fifth nerve at a rather earlier stage, it will be seen at once
that there is a very close resemblance between the two; the sole
point of difference being that in fig. 1, though the nerve still
retains its primary attachment, the secondary has not yet been
actually acquired. Balfour’s figures and description, already
referred to, show that at a still earlier stage the fifth nerve has
exactly the same appearance and relations which the seventh has
in fig. 2; and it is mainly on this fact, coupled with the close
similarity between such specimens as those represented in figs. 1
and 3, that we rely in support of the explanation we have given
above of the development of the root of the fifth nerve.
Inasmuch as figs. 1 and 2 are taken from the same embryo, it
would seem that the fifth nerve appears before the seventh, and
is, during the earlier phases of development, just one stage ahead
of it in development. At a time (fig. 1) when the primary roots
of the fifth have already become widely separated by growth
of the brain-roof, and the secondary attachment (v @) is on the
point of being acquired, the two seventh nerves (fig. 2) are still
im contact with one another across the top of the unexpanded
brain-roof; and at stage «x the seventh nerve (fig, 3) is in
exactly the same condition as the fifth at the end of stage 1
fig. 1).
‘Our observations appear, therefore, to prove conclusively that
as concerns the seventh nerve, while the change of position of
the dorsal or primary root (vit a) is due solely to rapid growth of
the roof of the brain, the lower or ventral root (vit 3) is a new
and purely secondary attachment.
Whilst these results concerning the roots of the seventh are,
we believe, new as applied to Elasmobranchs, they are in perfect
accordance with the account previously given by one of us of the
development of the seventh nerve in the chick, in which the
very same series of changes—the separation of the primary
roots by growth of the brain-roof, and the acquiring of new or
secondary roots—are shown to occur in a precisely similar man-
ner.! The close correspondence between these two very different
types of vertebrates is of much interest, partly as tending to
confirm the correctness of the account, and partly as showing
1 Marshall, ‘‘Develop. of Cranial Nerves in Chick,” ‘ Quart. Journ.
Micr. Sci.,’ Jan., 1878, pp. 34 and 35.
The prediction there made, that the secondary attachment of the nerves
in Elasmobranchs would prove on further investigation to be acquired in
exactly the same manner as in the chick, is now completely verified.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM, 481]
that this curious shifting of the nerve roots, though clearly a
change of a secondary nature, must yet have been acquired very
early by Vertebrates.
The later stages of development of the roots of the seventh
also present points of great interest. Fig. 6 represents a trans-
verse section through the roots of the seventh nerve of the same
embryo of stage n, of which fig. 5 shows the rootsof v. The
seventh nerve is seen to rise on either side by two roots, one
(vit a) from the top of the sides of the brain at the junction of
the thickened side with the thin roof, while the other (vm (3)
arises about half way down the sides of the brain. Between the
two roots the nerve is in contact with the brain, but apparently |
not connected with it. We have traced the intermediate steps
between figs. 3 and 6, and find that the upper root (vit a) of
fig. 6 is the original dorsal or primary root, and the lower one
(vit (3) the secondary root of fig. 3. In other words, there is
an important difference between the fifth and the seventh,
inasmuch as in the former the primary root is lost and the
secondary alone retained, whilst im the latter both primary and
secondary roots are retained up to stage N, and, indeed, as we
shall see immediately, throughout life. The difference between
the roots of the fifth and seventh nerves just noticed, does not
occur in the case of the chick, in which the primary root of the
seventh is lost as completely as is that of the fifth in Hlasmo-
branchs.* :
This shifting of the roots of origin and acquiring of a
secondary connection with the sides of the brain is not confined
tothe cranial nerves. It has already been shown to occur in the
posterior roots of the spinal nerves of the chick,? and occurs also
in the posterior roots of the spinal nerves of Elasmobranchs,
It is a point of much interest to note that the seventh nerve, in
the retention of its primary as well as its secondary root, 7s not
only more primitive than the fifth, but more primitive even than
the spinal nerves.
The condition of the roots of the seventh at stage o is shown
in the left hand side of fig. 9, representing half of a transverse
section through the hind brain and roots of origin of this nerve.
The two roots, the primary (vi a) and the secondary (vm (3),
are even more distinct than at the earlier stages. The primary
root (vit a) arises as before from the top of the thickened side
of the hind brain just before its junction with the thin roof;
from this origin the root runs downward, alongside of, and
closely applied to the brain, but unconnected with it, to join the
1 Marshall, ‘ Quart, Journ. Micr. Sci.,’ Jan., 1878, pp. 24 and 25.
.” Marshall, “On the Early Stages of Development of the Nerves in
Birds,” ‘ Journal of Anatomy,’ vol. xi, 1877.
482 PROF, MILNES MARSHALL AND W. B, 3PENCER,
secondary root (vi 3). This latter is now situated still nearer
to the ventral surface than at its first appearance, the distance
hetween the two roots being considerably greater than at the
earlier stages, as is evident from a comparison of fig. 9 with
fig. 6. The two roots also differ histologically, the dorsal or
primary root consisting almost entirely of elongated fusiform
cells, whilst the ventral root (vir (3) is mainly composed of
spherical ganglion cells.
This ventral root, at stage o, has, as shown in the figure, two
distinct attachments to the brain, one just below the other. It
is shown in longitudinal and vertical section at stage N in
_ fig. 11, where the brain presents opposite to its point of origin
an external bulging precisely similar to that opposite to the
secondary root of the fifth (v 3). The dorsal or primary root
(vir a) is shown at the same stage in fig. 12.
In fig. 14 the two roots of the seventh are seen in longitu-
dinal and vertical section, at an age intermediate between stages
oandp. The dorsal root (vir a) arises very far up the sides
of the brain, in fact, as in the earlier stages, from the junction
of side and roof; itis of considerable length, is widely separated
from the secondary root, and still consists mainly of fusiform
cells ; the secondary or ventral root, which is overlaid and almost
concealed by the primary root, is only seen in part, its most
anterior portion alone being visible.
The dorsal or primary root is also well shown at the same
stage in fig. 15.
B. Comparison of the embryonic roots of the fifth and seventh
nerves with those of the adult.—It will be convenient here to
briefly summarise our results concerning the roots of origin of
the fifth and seventh nerves, and to trace their changes up to
the adult form.
About the close of stage 1 the fifth nerve (fig. 1) still retains
its primary attachment (va) to the brain, and is on the point
of acquiring its secondary one (v 8): owing to the growth of
the roof of the brain the two primary roots, which were at
first continuous across the top of the brain, are now widely
separate. The seventh nerve (fig. 2) arises by its primary root
from the dorsal summit of the brain, whose roof at this point
has not yet commenced its rapid growth, so that the nerves of
the two sides are still directly continuous with one another ;
there is as yet no trace of the secondary root of the seventh.
At stage x the fifth nerve (fig. 4) has completely lost its
primary root and is now attached to the brain by the secondary
root alone (v (3); a slight trace of the former-is still present as
a small dorsal projection on the nerve just beyond the root of
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 483
attachment. ‘Towards the close of stage k, the tertiary or anterior
roots have appeared, arising almost certainly as outgrowths of
the ganglion towards the brain ; but whether these are altogether
new developments or merely new attachments of the primary
root is uncertain. The seventh nerve (fig. 3) is in the same
condition as the fifth at the preceding stage; it is now attached
by both primary and secondary roots, the former, owing to
the growth of the brain-roof, being widely separate from one
another.
At stage N the condition of the roots is much the same as at
the end of stage xk. The fifth nerve (figs. 5 and 11) is attached
by its secondary and tertiary roots, the latter being very con-
stantly two in number, of which the anterior is the larger and
attached to the brain some distance in front of the seeondary
root (v 8). The seventh nerve (figs. 6, 11 and 12) is attached
by both primary and secondary roots, the nerve between the
two being in contact, but not in connection with the brain; the
secondary root (fig. 11) is divided into an anterior or facial, and
a posterior or auditory division.
At stage o (figs. 8 and 9) the chief differences are—first,
that, owing to increased growth of the brain, the distance
between the primary and secondary roots of the seventh nerve is
much greater than before; secondly, that the roots of the fifth
and seventh nerves, which, from the first, have been quite inde-
pendent of one another, are now situated much closer together
than they were at the earlier stages.
At stage o-p (fig. 14) the two roots of the seventh (vi1a and
vit (3) are still further apart from one another, but are now very
close to those of the fifth. The connection between the two
nerves which we have already seen is fully established at stage x,
and which is shown at stage Lin fig. 10 (N.c’.) and at stage n in
fig. 11 (N.c’.), is, by stage o-P, very much more extensive and
intimate than previously. The roots of the nerves are still quite
distinct from one another (fig. 14), but immediately beyond
these roots the two nerves become so closely and extensively
united together that it is impossible to draw a line of separation
between them. ‘The connection is rendered still more intimate
by the crossing of one of the branches of the seventh, as will be
described fully later on, over the main stem of the fifth, so as to
lie in front of the branches of this nerve.
The condition of the roots, as of the branches, of the fifth and
seventh nerves at stage o-P differs but little from that of the adult,
the sole change of importance as concerns the roots being that
the ventral roots (v 8 and vir 3) approach still closer together,
and come into actual contact.
The primitive distinctness, gradual approximation, and ulti-
484 PROF, MILNES MARSHALL AND W. B, SPENCER.
mate more or less complete fusion of the roots of the fifth and
seventh is of great interest, as proving that the fusion of these
two nerves, so characteristic of Pisces and Amphibia, is a purely
secondary feature, and that the two are at first as independent of
one another in these forms as they are throughout life in the
higher Vertebrates.
In adult Elasmobranchs the combined roots of the fifth and
seventh nerves are usually described together, and the descrip-
tions of different observers, though not quite in harmony with
one another in certain details, yet agree fairly well on the main
points. Stannius, whose descriptions are the most elaborate,
describes the combined fifth and seventh nerves as arising in
Plagiostomes by three roots,! of which one is seen on closer exa-
mination to be double, giving four roots in all; of these the first,
or most anterior one, arises from the ventral surface of the
medulla by two short non-ganglionic roots, which unite together
shortly after leaving the brain. This root is in Raa, according
to Stannius, mainly motor, supplying the muscles by which the
respiratory movements of the anterior wall of the spiracle are
effected, and also certain others in connection with the jaws.
The second root of Stannius is large, lies posterior to the first,
and is in close proximity behind with the auditory nerve ; it
may be distinguished into an anterior part which belongs to the
trigeminal, and a posterior, more ventrally situated portion,
which belongs to the facial. The third root is very large and
much more dorsally situated than the other; it is connected by
its deeper fibres with the second root, whilst, from its superficial
fibres are derived, according to Stannius, the ramus ophthalmicus
superficialis of the fifth, and also, in part, the maxillary and
buccal nerves.
Gegenbaur,” in his account of the cranial nerves of Hexanchus,
distinguishes between the roots of the fifth and the seventh.
He describes the fifth as arising by the union of two trunks of
about equal size, an anterior and a posterior; of these the ante-
rior (a) arises from the ventral surface of the medulla by two
roots situated very close together ; the posterior (4) has also two
distinct roots, a dorsal one (a) arising from the side of the
medulla by a large swelling projecting into the fourth ventricle,
and a ventral one (3) situated immediately above the root of the
facial, and in front of, and above that of the auditory.
The seventh nerve in Hexanchus is described as arising by two
1 Stannius, ‘Das peripherische Nervensystem der Fische.’? Rostock,
1849, pp. 29 and 30.
2 “Ueber die Kopfnerven von Hexanchus,” ‘Jenaische Zeitschrift,’
Ba. vi, 1871, pp. 501, 502, and 5138, 514,
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM, 485
roots, a larger one immediately in front of the auditory, and a
smaller one passing to it from the fifth.
Jackson and Clarke’ describe the combined fifth and seventh
nerves in Lehinorhinus as arising by three roots; an anterior
inferior root (v a), itself with two well-marked rootlets, a second
root (v 3) arising by a well-marked superior rootlet from the
lobus trigeminus and by a smaller inferior one, and a third root
(v y and vit) closely connected with the second one.
Balfour? describes the fifth nerve in Scyddiwm stellare as arising
by three roots :—(1) an anterior more or less ventral root; (2)
a root rather behind this arising by two strands, a dorsal and a
ventral, and closely connected behind with the root of the
seventh; and (3) a quite distinct dorsal and posterior root
situated slightly behind the dorsal strand of the second root.
The seventh nerve is described as arising by a single root close
to, and behind, the second root of the fifth.
On comparing these descriptions of adult Elasmobranchs with
our own observations on embryos and adults we are led to the
following conclusions :
The fifth nerve in the adult arises by two roots :
a. An anterior one arising from the ventral surface of the
medulla by two non-ganglionic rootlets, whose distinctness varies
much in different adult Elasmobranchs. These rootlets are the
tertiary or anterior roots of our embryos (figs. 10, 11, and 14,
vy). This root corresponds to the first root of Stannius, the
anterior root (a) of Gegenbaur, the anterior inferior root (v a)
of Jackson and Clarke, and the anterior root (1) of Balfour.
6. A posterior larger ganglionic root, the ventral or secondary
root of our embryos (figs. 10, 11, and 14, v3). This is at first
quite distinct from the root of the seventh, but during the later
stages of development gradually approaches this latter, and in
the adult cannot be clearly distinguished from it.
This root is the anterior part of the second root of Stannius ;
the ventral division ((3) of the posterior root (4) of the fifth of
Gegenbaur; apparently the inferior rootlet of the second root
(v 6), and possibly part of the third root (vy and vit) as well, of
Jackson and Clarke; and the second root (2) of the fifth of
Balfour.
The seventh nerve in the adult arises by two roots:
a. A dorsal root arising far up the side of the medulla, at the
junction of the thickened sides and thin roof of the fourth ven-
tricle. This root is the primary or dorsal root of the seventh
nerve of our embryos (figs. 2, 3, 6, 9, 12, 14, and 15, vir a),
* “The Brain and Cranial Nerves of Zehinorhinus spinosus.” ‘Journal
of Anat. and Phys.,’ vol. x, p. 81 ,
2 Op. cit., pp. 194 and 195,
486 PROF. MILNES MARSHALL AND W, B. SPENCER,
It has by previous observers been almost invariably described as
a root of the fifth, and never as a true root of the seventh; ow
description and figures here given leave no room for doubt that it
belongs to the seventh. As already noticed, the retention of this
root marks the seventh as being more primitive than the spinal,
and possibly more so than any of the other cranial nerves, all
the other nerves apparently retaining their secondary roots only.
This root is the third or dorsal root of Stannius; the dorsal
rootlet (a) of the posterior trunk (4) of the fifth of Gegenbaur ;
the superior rootlet of the second root (v (3) of Jackson and
Clarke, and the dorsal and posterior root (8) of the fifth of
Balfour.
6. A ventral root arising from the side of the medulla at a
rather lower level than the posterior root of the fifth. This is
the secondary or ventral root of the seventh of our embryos
(figs. 8, 6, 9, 10, 11, and 15, vir (3). The auditory nerve is at
first derived from this root, but in the adult appears to be more
distinct from the facial than is the case in the embryo. This
root is, at first, some little distance behind the secondary one
(v 8) of the fifth nerve (figs. 10 and 11), from which it is
perfectly distinct; in the later stages the two roots gradually
approach one another (fig. 14), and in the adult are usually in
close contact.
This root is the posterior part of the second root of Stannius,
the root of the seventh of Gegenbaur; part, or possibly the
whole of the third root (v y and vit) of Jackson and Clarke;
and the single root of the seventh of Balfour.
It would appear, therefore, that the fifth nerve loses its pri-
mary root, retains its secondary, and acquires tertiary roots,
while the seventh retains both primary and secondary. Con-
cerning the fourth nerve we would suggest the possibility that
it may prove to be the primary root of a nerve of which the
third nerve is the secondary root, which has, in this case,
acquired complete independence.
c. Lhe branches of the seventh nerve.—At stage k the seventh
nerve, which, as we have already seen, has acquired its secondary
as well as its primary roots of origin (fig. 3), expands below the
secondary root into a large ganglionic swelling lymg immediately
behind the third head cavity. From this enlargement three
branches arise: (1) from the anterior and superior angle of the
ganglion a large nerve with a ganglionic base arises, and runs
forward along the dorsal surface of the head, lying just beneath
the superficial epiblast; this is the ophthalmic branch of the
seventh, and is referred to in our figures as VII a.
(2) The second branch, which is also large, and has a
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 487
ganglionic base, arises from the front part of the ganglion
immediately below the root of the ophthalmic ; its deeper portion
runs forwards and slightly downwards over the top of the third
head cavity, and becomes connected with the main stem of the
fifth ; it is referred to in the figures as V. c’. The more super-
ficial portion passes on further forward in the same direction,
crosses the mandibular arch, and enters the maxillary process,
lying immediately superficial to the maxillary nerve, and just
beneath the external epiblast ; it is referred to in the figures as
vil d.
(3) The third branch is the direct continuation of the main
stem of the facial nerve; it runs downwards and backwards
along the anterior border of the hyoidean arch, and is the rudi- —
ment of the posterior or hyoidean branch of the seventh in the
adult ; it is referred to in the figures as VII c.
Of these branches the first, or ophthalmic, is from its earliest
appearance connected with the dorsal or primary root of the
seventh rather than with the ventral root. The second branch
is the most remarkable of the three; its deeper portion forms,
as we have seen, a direct connection between the fifth and
seventh nerves, a communication which appears to be very early
established, inasmuch as by stage x the connecting branch is
already a nerve of considerable size; the superficial portion of
this branch (vir @) is noteworthy, mainly on account of its very
close relations with the maxillary division of the fifth nerve.
At stage t the only changes of importance are, (1) that the
several branches have increased in size, and, excepting the branch
vit d, which has a very straight course, and ends abruptly in
the skin, have divided into secondary branches near their termi-
nations; and (2), that a small anterior branch has arisen from
the hyoidean nerve (vit c), some distance from the brain, which
runs forward over the top of the spiracular or hyomandibular
cleft, and then down in the anterior wall of the spiracle, ¢. ¢. in
the posterior portion of the mandibular arch; this branch will
be referred to as vit 0.
The several branches of the seventh nerve at stage N are well
shown in the diagrammatic figures 1] and 12. The ophthalmic
branch (vit a) is seen in fig. 12 arising from the base of the
primary or dorsal root (vit a) as a stout nerve, which expands very
shortly after its origin into a large somewhat fusiform ganglion,
beyond which the nerve runs forward as a stout trunk to the
extreme anterior part of the head. ‘Throughout its course it
lies just beneath the external epiblast, and immediately dorsad of
the ophthalmic branch of the fifth (v a), with which it is in very
close relation ; like this latter nerve it gives off branches along
its whole course to the integument of the neighbouring parts,
488 PROF, MILNES MARSHALL AND W. B. SPENCER.
the branches being few in number at the proximal end, and
much more numerous distally. A short distance before its
termination this nerve, like the ophthalmic branch of the fifth,
is crossed at a considerable angle by the nerve JW (fig. 12).
The connecting branch (WN. c’.) between the seventh and fifth
nerves is well seen in figs. 11 and 12; it is now shorter and
wider than at stage t (fig. 10), and contains very numerous
ganglion cells along its whole length.
The superficial portion of this nerve (vit @) is not shown in
fig. 11, but is represented along its whole length in fig. 12 ; it
is a stout nerve with a remarkably straight course ; it gives off
no branches at all along the greater part of its length, but near
its distal termination divides rather suddenly into a number of
branches, which end in the integument of the maxillary process,
the most anterior of the branches extending forwards almost as
far as the hinder border of the olfactory pit. The relations of
this nerve to the maxillary branch of the fifth are very curious ;
the two nerves are very close together, the branch of the seventh
lying, as at the earlier stage, immediately superficial to that of
the fifth. These relations are well seen in the transverse section
drawn in fig. 6. ‘This shows, as already noticed, the primary
and secondary roots of the seventh, and also the proximal portion
of the nerve vir d. This nerve is seen to be a direct continua-
tion of the primary root; its inner, or deeper, portion is seen on
both sides to become continuous with the maxillary branch of
the fifth, (v 2), the junction of the two forming the connection
between the fifth and seventh nerves already noticed. Beyond
this point of union the nerve vit d is continued downwards, lying
immediately superficial to the maxillary nerve (v4). The two
nerves preserve this relation up to their terminal distribution,
two of the ultimate branches being represented in figure 5 (v 4
aud vit d@). This very remarkable branch of the seventh puzzled
us greatly for a long time, and it was only after working out the
whole history of its development up to stage q that we succeeded
in determining its import. The nerve has already been described
and figured by one of us,’ and named tentatively the palatine.
This determination now proves to be erroneous; the palatine is a
deep-lying nerve, whereas the nerve vir d retains its superficial
position in the adult.
This nerve (vt d) we have now identified as the buccal nerve,
the proof of this determination, consisting in our having traced
the nerve directly up to the adult. The buccal nerve has always
hitherto been regarded as a branch of the fifth, and is described
1 Marshall, loc. cit., pp. 86, 87, and Pls. V, fig. 15; and VI, figs. 28
and 29.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 489
as such by Stannius,' Gegenbaur,” Jackson and Clarke,’ Balfour,*
and others. Stannius’ points out that the buccal nerve in fishes
is very variable; that it may either arise from the main stem of
the fifth, from the maxillary or the mandibular, or from both
these nerves, or, finally, may be absent altogether.
Up to stage N, as shown in figures 6, 11, and 12, the buccal
nerve is clearly a branch of the seventh, and could not possibly
be taken for a branch of the fifth. After stage n, however, the
connection between the roots of the fifth and seventh nerves
becomes, as we have seen, very much more intimate; and at the
stage between o and p, represented in fig. 14, the buccal nerve
(vir d@), which is now situated completely in front of the maxillary
(v 4), might very easily be taken for a branch of the fifth rather
than of the seventh; careful examination shows, however, that
the buccal, which is, as before, the most superficial of all the
ventral branches, can be traced up to the dorsal root of the
seventh from which it arises, as in the earlier stages.
This origin of the buccal nerve from the root vita has
already been noticed by Stannius,° who, however, as we have
seen, did not refer the root in question to the seventh. Stan-
nius’ figure of the nerve in Chimera’ shows clearly the very
superficial position of the buccal nerve and its independence of
both maxillary and mandibular nerves.
Of the remaining branches of the seventh the anterior one
(vir4) is shown im fig. 11 at its origin arising from a large
ganglionic swelling on the main or hyoidean branch of the
seventh, and running forward in close contact with the top of
the spiracle (sp.), in front of which it divides almost at once
into two branches, the distribution of which is shown in fig. 12;
of these the anterior one (vit ya) runs downwards, forwards, and
inwards, giving off numerous branches to the roof of the mouth.
Im fig. 12 the anterior branches of this nerve appear to cross
the posterior branches of the buccal, but it must be borne in
mind that at this point the two nerves are at very different
levels, the buccal beiug very superficial and the nerve (vit pa)
lying very deep. This latter is seen in transverse section in
fig. 7, which shows, on the right side, its origin from the
ganglion, and, on the left, its distribution to the mucous mem-
brane of the mouth. By comparing this figure with fig. 6, the
1 Handbuch der Zootomie,’ p. 158.
2 Loe. cit., p. 509.
3 Loc. cit., p. 86.
4 Op. cit., p. 195.
5 *Das Peripherische Nervensystem,’ pp. 41 and 42.
5 Loe. cit., p. 30.
7 Loe. cit., Mal 1, fig. 1.
490 PROF. MILNES MARSHALL AND W. B,. SPENCER.
difference of levels between the two nerves will be at once appa-
rent. This anterior branch (vit pa) is the palatine nerve ; it has
already acquired by stage n its characteristic distribution, and
undergoes no further change of importance from this period up
to the adult stage.
The second or posterior division (fig. 12, v1 sp) of the nerve
(virZ) runs downwards and slightly backwards along the ante-
rior border of the spiracular cleft; it gives off branches along
the whole of its length, the great majority of which run back-
wards to the mucous membrane of the border of the cleft and to
the spiracular branchia. This nerve, which at this stage is of
about equal size with the palatine, is the spiracular or pre-
spiracular nerve of zootomists.
The only branch of the seventh still left for description is the
main trunk or hyoidean branch (fig. 11, vite), which forms the
direct continuation of the main stem of the nerve. This, as is
seen from fig. 11, arises from the ventral or secondary root of
the seventh, and is at its origin closely connected with the
auditory nerve (v1). Immediately after the auditory nerve
leaves it, the facial forms a ganglionic swelling from which the
communicating branch (J. c’.) to the fifth nerve is given off ;
beyond this point it is continued for a short distance as a stout
nerve with comparatively few ganglion cells; this very speedily
dilates into the large ganglionic swelling on the top of the
spiracular cleft, from which the anterior branch (vir 4) is given
off. The main stem of the seventh (vit c) continues its course
downwards, running along the anterior border of the hyoid arch
and very close to the posterior border of the spiracular cleft ;
during this part of its course it contains few or no ganglion cells, |
it gives off a number of branches, of which the first is the largest,
from its posterior border which supply the muscles derived from
the wall of the third head cavity (3). A short distance below
the lower edge of the spiracular cleft the nerve divides into two
branches, of which the anterior (vit cl.) runs forward along the
lower border of the mandibular arch, sending numerous branches
to the integument of this part and extending forward so as to
come into very close relation with the posterior branches of the
maxillary division of the fifth (v4). The posterior of the two
branches (vic, 2) into which the seventh divides continues
the direction of the main stem, and runs down in the hyoid
arch just in front of the third head cavity, in the terminal dilata-
tion of which it ends. Of these two terminal branches of the
seventh, the anterior, sensory, and superficial one is the ramus
mandibularis externus of Stannius! and Gegenbaur,? while the
1 Loe. cit., p. 65.
* Loe. cit., p. 514.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 49]
posterior, muscular, and deep branch is the ramus mandibularis
internus v. profundus of the same authors. Both these branches
have already acquired, by stage n, not only the characteristic
distribution of the adult nerves, but nearly all the minor branches
as well.
To recapitulate ; we find that by stage nN the seventh nerve
has acquired all the important branches of the adult nerve, the
main trunks and many of the branches being fully developed at
a much earlier period—stage L. ‘The seventh nerve at stage N
has two roots, a dorsal or primary, and a ventral or secondary.
From the dorsal root (v11 a) arise two branches: (1) the ophthal-
mic (vila) and (2) the buccal (vm d@), both of which appear to
be purely sensory nerves. The connecting branch (J. ¢’.) to the
fifth nerve, though it appears in longitudinal section (fig. 11) to
be a distinct branch, in transverse sections (fig. 6) seems to be
only the deeper portion of the buccal nerve. From the ventral
root arises the main or hyoidean branch (vite), from which the
branch vir runs forward over the top of the spiracle, dividing,
almost immediately, into the palatine (ya) and ‘spiracular (sp)
nerves, whilst the hyoidean itself divides distally into the sensory
ramus mandibutaris externus (V ¢, 1) and the motor ramus mandi-
dularis internus (Vc, 2).
The Sixth (Abducens) Nerve.—Concerning the development
of the sixth nerve our observations simply confirm the account
already given by one of us.!
The whole length of the nerve is shown in longitudinal and
vertical section in fig. 13 (v1), where it is seen arising from the
base of the brain by a number of small non-ganglionic roots
which unite to form a slender nerve; this nerve runs forwards a
short distance, then turns downwards, pierces the investing
mass (7. v.), and ends in the posterior extremity of the rectus
externus muscle (1. é.). .
Fig. 7 shows the sixth nerve in transverse section at the same
stage (N): on the left side of the figure the termination of the
nerve in the rectus externus is seen; while on the right side,
which is taken from a more posterior section, one of the roots
of origin is seen. This figure shows that the roots of the
sixth are considerably nearer the mid ventral line than are the
secondary roots of the seventh nerves, and also that the sixth
and seventh nerves are quite independent of one another. At
stage N the sixth nerve appears to be altogether behind the
seventh, but in stage o it is situated rather further forwards,
so that the same section may pass through the roots of both
nerves.
! Marshall, loc. cit., pp. S9—93.
VOL. XXI.—NEW SER. KK
492 PROF, MILNES-MARSHALL AND W. B, SPENCER.
We have not yet detected the sixth nerve in embryos younger
than stage L: concerning the morphological value of this nerve
we adhere to the opinion already expressed that it is to be
viewed as bearing the same relation to the seventh that the
anterior root of a spinal nerve does to its posterior root.
The Eighth (Auditory) Nerve.—This nerve also we can
dispose of briefly: at stage K it appears as a large ganglionic
posterior branch of the seventh nerve, given off immediately
beyond the root of origin. It is from the first connected with
the ventral or secondary root (vii 3). The condition at stage
L is shown in fig. 10 (vit1). At stage N (fig. 11) its root, though
still intimately connected with that of the facial, shows a very
evident line of separation from it; the ganglionic character of
the auditory nerve placing it in marked contrast with the non-
ganglionic root of the facial. This distinction between the two
roots becomes more marked in the later stages.
General Considerations.—Several questions of a more general
character arise out of the facts we have recorded above, and
we propose to conclude the present paper with a brief notice of
the more important of them. The problems in connection with
the roots of origin of the nerves have been already sufficiently
discussed, so that we turn at once to the consideration of their
branches, concerning which the most important points are the
determinations of the equivalence of the branches of the different
nerves to one another.
We commence with the ophthalmic branches of the fifth and
seventh nerves, the branches named v a and vita in our figures.
These two nerves, whose courses and relations are well shown in
figs. 11 and 12, accompany one another very closely along
their whole length; they appear to be both sensory nerves, their
branches being distributed exclusively to the skin of the top
and front of the head, and more especially to the mucous canals
of these parts. Of the two nerves the branch of the fifth nerve
(v a) is the smaller and the more ventrally placed of the two:
though the smaller, its branches are, especially in the earlier
part of its course, more numerous than those of the seventh.
The two branches in their course through the orbit Ze dorsad of
all the other contents of the orbit. They are at first quite dis-
tinct from one another (figs. 11 and 12) and lie close beneath
the external epiblast (fig. 5, vi a); the branch of the seventh
being the more superficial of the two. In the later stages of
development, as in the adult, the two nerves lie in very close
contact with one another (fig. 16, va and vir a), the branch of
the seventh lying immediately dorsad of the branch of the fifth ;
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 493
they also, as shown in fig. 16, lie at a deeper level than at
the earlier stages.
The fourth nerve bears, as already noticed, a very close rela-
tion to these branches. As shown in figs. 1] (av) and 16 (1y) it
crosses the ophthalmic branches at right angles, lymg at a
slightly deeper level but turning outwards immediately beneath
them, to end in the superior oblique muscle (0. s.). At the point
of crossing the branches of the two nerves are in very close rela-
tion with one another, and we are inclined to believe that a
communication exists between the fourth nerve and the ophthal-
mic branch of the fifth at this point, though we have failed to
determine this with certainty. ;
In determining the morphological value of these ophthalmic
branches of the fifth and seventh nerve, very valuable evidence,
by which we have been much influenced, is afforded by the con-
dition of the glossopharyngeal nerve. ‘This nerve, at stage L,
gives off, just beyond its root of origin, a slender dorsal branch
(fig. 10, rx @), which, at first passing upwards and backwards,
soon curves round the hinder end of the auditory vesicle (aud.),
and reaching the dorsal surface of the head, runs forward a
short distance, lying immediately beneath the superficial epiblast.
It gives off branches along its whole course, which are distributed,
as shown in the figure, to the integument of the top of the head.
At stage N this nerve (fig. 12, 1x a) has the same course and
appearance, the only differences being that it extends rather
further forwards than at the earlier stage, so as to reach some
distance in front of the middle of the auditory vesicle; and,
secondly, that its branches are now seen to be in connection with
the commencing mucous canals of this region. This branch of
the ninth nerve is clearly the ramus dorsalis, and an examina-
tion of the figures 11 and 12 will, we think, leave no doubt that.
the nerves vit a and v a, which have a similarly superficial course
and a like distribution to mucous canals, must be viewed as the
equivalent branches of the seventh and fifth nerves. We are,
therefore, led to adopt the view put forward by Balfour, that
the ophthalmic branches v @ and vit a of the fifth and seventh
nerves are the rami dorsales of these nerves. Stannius and
_) In my paper on the head cavities of Elasmobranchs I abandoned the
view previously put forward (this Journal, Jan., 1878, p. 30), that the
ophthalmics were persistent remains of the commissure connecting to-
gether the roots of the nerves at their first appearance, but did not expressly
adopt the view that they were rami dorsales. I have been led to adopt
this view mainly because it now appears that, instead of being perfectly
exceptional in their course, as I had previously supposed them to be, the
ophthalmics merely express an exaggerated condition of a state of things
shown in a less extreme form by the ramus dorsalis of the glossopharyn-
geal.—A. M. M.
494, PROF, MILNES MARSHALL AND W. B. SPENCER.
Gegenbaur speak of the ophthalmics as rami dorsales, but refer
them entirely to the fifth.
What the causes are which have led to the very marked
extension forwards of the rami dorsales of these nerves is not
very evident ; we would suggest that it is due mainly to an
extension forwards and accumulation at the anterior end of the
head of the special tegumentary sense organs—the mucous
canals—this extension forwards involving a corresponding exten-
sion of the nerves supplying these organs; in connection with
this suggestion it is of interest to note that no one of the nerves
in front of the fifth sends any branches to these organs. Whether
there is any trace of a ramus dorsalis to the third is very doubt-
ful; at any rate the fourth nerve cannot be the ramus dorsalis
of the third, as its course is, at first, at right angles (fig. 11) to
the rami dorsales of the fifth and seventh nerves; and, secondly,
it is a motor and not a sensory nerve.
We now come to a far more intricate problem, viz. the import
of the connecting branches between the third, fifth, and seventh
nerves, with which it will be convenient to consider the nerve J.
(figs. 10, 11, 12, and 15).
These three nerves, VV. c., V.c.’ and WV. all appear very early ; we
have failed to determine the date of their first origin, but by
stage K they are fully established. The posterior one (J. ¢’.),
connecting the fifth and seventh nerves together, is the most
difficult to investigate, owing to its appearing from the first as
merely the deeper portion of the buccal nerve (fig. 6); in longi-
tudinal sections, however, it appears very distinct (vde fig. 10).
It is from the first much shorter than either of the other two
nerves we are considering, and in the later stages (fig. 14) and
the adult condition, owing to the close approximation of the fifth
and seventh nerves, ceases to be visible as a distinct trunk.
The second of the three nerves (J. c., figs. 10 and 11) forms, as
already noticed, a direct connection between the Gasserian gan-
glion of the fifth and the ciliary ganglion (c.g.) of the third
nerve, and is much more slender than WV. c’. Concerning the
nerve in question, it is of the utmost importance to notice that not
only is it fully established at the stage at which our observations
commence, but that it is from the very first a connecting nerve,
and that there is no reason whatever in the early stages for con-
sidering it as belonging to the fifth rather than to the third nerve.
We have, therefore, in this paper given it a perfectly neutral
name,
The last of these nerves, W., is still more remarkable; like the
others it is present at K. Starting at this stage from the ciliary
ganglion it runs an almost perfectly straight course to the anterior
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM, 495
end of the head, ending abruptly in the external epiblast, and
giving off no branches whatever. At stage L it is in very close
relation to the olfactory nerve, and in some specimens seems to
be connected with it, though we cannot speak with certainty on
this point.
As soon as the eye muscles are established they have very
definite relations to this nerve; the rectus superior and internus,
and the od/iquus superior lying above it, and the remaining three
muscles below it (fig. 11). It also passes through the substance
of the sclerotic, as noticed in a former portion of this paper.
Concerning the morphological significance of these nerves,
bearing in mind their very early appearance and the total absence
of evidence for regarding them as branches of either of the
nerves they serve to connect, we are disposed to view the nerves
NV.c. and JN. c.’ as persistent portions of the neural ridge between
the outgrowths to form the third, fifth, and seventh nerves, and
as being, therefore, homologous with the primitive commissure
connecting the posterior roots of the spinal nerves together.1_ As
to the nerve VV. we are much more in doubt; its apparent con-
nection with the olfactory nerve at L, if confirmed, would tell in
favour of its being regarded as a similar commissure between
the third and olfactory nerves, and would greatly support views
previously advanced by one of us concerning the morphological
value of the olfactory nerve.” On the other hand, the extension
forwards of the nerve WV. beyond the olfactory nerve to the
extreme anterior end of the head must, for the present, be
regarded as almost conclusive against its commissural nature.
In this case it can only be a branch of the third nerve, for the
only other nerve with which it is in direct, or indirect, connec-
tion is the connecting nerve (V.c.) between the third and fifth,
which, if it does not belong to the third, there is at any rate no
reason for referring to the fifth.
In the adult Scy/Ziwm this nerve retains the relation to other .
nerves which it has clearly acquired by stage N; it is described
in the adult by Schwalbe? as “ dieser scheinbare Zweig des Oculo-
motorius.” In Mustelus Schwalbe describes it as a branch of
the fifth. We much regret that we have had no opportunity of
studying the development of this nerve in Afustelus ; should it
prove to arise as in Scy//iwm, then it must definitely be regarded
as a branch ofthe third.
As we have already pointed out, the nerves V. c. and WV, toge-
‘ For these commissures in Elasmobranchs, vide Balfour, op. cit., pp. 158
—160, and Pl. XI, fig. 18, and Pl. XLV, fig. 154. In the chick, Marshall,
‘Quart. Journ. Mier. Sci.,’ Jan., 1878, Pl. LI, figs. 27 and 28,
? Marshall, ‘Quart. Journ. Mier. Sci,’ vol. xix, pp. 300 seq.
3 Schwalbe, ‘ Das Ganglion Oculomotorius,’ p. 16.
496 PROF. MILNES MARSHALL AND W. B. SPENCER.
ther make up the ramus ophthalmicus profundus of zootomists, a
nerve which seems to have escaped Balfour’s notice both in the
adult and in the embryo. Balfour does, indeed, in his descrip-
tion of the nerves of the adult Scy/lium, speak of a ramus
ophthalmicus profundus, but imasmuch as he says concerning it
that “ this latter nerve arises from the anterior root of the fifth,
separately pierces the wall of the orbit, and takes a course slightly
ventral to the superior ophthalmic nerve, dwt does not (as is
usual in Elasmobranchs) run below the superior rectus and
superior oblique muscle of the eye,’ itis clear that he is describ-
ing the ophthalmic branch of the fifth and not the true profundus,
whose existence he has overlooked. There appears to be con-
siderable confusion in the use of the terms ramus ophthalmicus
superficialis and ramus ophthalmicus profundus by different
writers, a confusion which our observations on Scyllium may
help to remove. We find, as already stated, three perfectly dis-
tinct nerves to which the term ophthalmic nerve can be, and is,
applied; of these the two dorsal ones (v a and vita of our figures)
are the rami dorsales of the fifth and seventh nerves, and may be
spoken of as the ophthalmic branches of the fifth and seventh
nerves respectively. Both these nerves are very superficial along
their whole course, and doth lie dorsad of all the eye muscles
and other contents of the orbit. The two nerves are at first per-
fectly distinct, but in the adult unite more or less closely toge-
ther, the extent of their union varying much in different Hlasmo-
branchs; the two together constitute the ramus ophthalmicus
superficialis.
The third of the ophthalmic nerves, the ramus ophthalmicus
profundus, has a very different course, and is of a totaily different
nature ; it is formed in Scyddiwm by the union of the connecting
branch between the fifth and third nerve (NV. c.) with the branch
n of the third nerve. It is very definitely characterised by its
course ventrad of the superior rectus, superior oblique, and internal
rectus muscles, by its close relation with the inner wall of the
eyeball, by the fact that the ciliary ganglion is either in its trunk
or is connected with it directly, by its having at first no branches
and by its close connection with the olfactory nerve.
We believe that the ophthalmicus superficialis and ophthal-
micus profundus always maintain these relations; that the pro-
Fundus, which is clearly the nasal nerve of Mammaiia, is a primi-
tive and very constant nerve, and that it uever shifts its position
so as to lie dorsad of all the eye muscles, as supposed by
Balfour.
The two divisions of the ophthalmicus superficialis, on the
other hand, appear to be very variable indeed in different Verte-
1 Op. cit., p. 194: the italics are our own.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 497
brates ; they attain their maximum development in the Hlasmo-
branchs, probably on account of the great development and
importance of the organs they supply—the mucous canals. In
Mammalia the ophthalmic branch of the fifth is represented by
the frontal and lachrymal nerves, while the seventh nerve has
no ophthalmic branch.
It would hardly be profitable to discuss the various descrip-
tions of these nerves by different writers; we will merely point
out here that Schwalbe! clearly distinguishes the three ophthal-
mic nerves. He calls, as we have done, the ophthalmic branches
of the seventh and fifth nerves together the ramus ophthalmicus
superficialis, distinguishing the component parts as portio major
(vita) and portio minor (v a) respectively. He also employs the
term ramus ophthalmicus profundus in the same sense as we have
done. Balfour, who was the first to clearly recognise the double
nature of the ophthalmicus superficialis, is in error in calling the
lower portion of it (va) the ophthalmicus profundus.
Concerning the other branches of the nerves in question, there
can be little doubt that the hyoidean branch (vii ¢) of the seventh
and the mandibular branch (ve) of the fifth are homologous
nerves, supplying respectively the anterior walls of the hyoidean
and mandibular arches; and there appear to be good reasons for
viewing the nerve (111 ¢) as the corresponding branch of the
third.’ All the three nerves in question are either mainly or
exclusively motor in function.
The seventh, like the hinder cranial nerves, forks over a
visceral cleft—the spiracle. As shown in figs. 11 and 12, there
are two branches of the seventh which run down in front of
the spiracular cleft, viz. the buccal (vir d) and the mandibular
(vit 4), which latter divides almost at once into the palatine and
spiracular nerves. Of these two a history of their development
and a comparison of the branches of the seventh with those of
the glossopharyngeal (1x, fig. 12), leave no possible room for
doubt that the mandibular branch (vir 4) is the homologue of
the anterior branch (1x 4) of the glossopharyngeal. This latter
nerve (Ix 4, fig. 12) extends very far forwards in the hyoidean
arch, being in this respect very closely imitated by the palatine
nerve (VII, pa), so that we are disposed to regard the whole of
the mandibular division (vit 4) of the seventh, 2. ¢. both palatine
and spiracular nerves, as together equivalent to the anterior or
hyoidean branch (1x 4) of the glossopharyngeal.
' “Das Ganglion Oculomotorius,” ‘Jenaische Zeitschrift,’ Bd. xiii,
pp. 11 seg.
? Marshall, loc. cit., p. 88.
498 PROF, MILNES MARSHALL AND W. B. SPENCER,
Balfour! describes the mandibular branch of the seventh as
being large in the embryo, so large in fact that he feels difficulty
about identifying it with the adult spiracular nerve. His
figures,' however, show perfectly clearly that what he describes as
the mandibular branch of the seventh is really the nerve we have
shown to be the buccal.?
The maxillary nerve (v 4) is, from its time and mode of
development, almost certainly to be regarded as the true anterior
branch of the fifth corresponding to the mandibular branch of
the seventh, although in the absence of a visceral cleft in this
region this determination cannot be considered absolutely proved.
Whether there is any equivalent branch of the third nerve is
very doubtful; at any rate no such branch can be pointed out
with certainty.
There now remains for consideration the buccal nerve, the
determination of which, as a branch of the seventh, is one of
the most striking points we have brought to light. Whether
this remarkable nerve has any homologue among the branches of
the fifth is a point our investigations have not yet enabled us
to determine. It is perhaps worth while pointing out that there
are many points of resemblance between this nerve and the ramus
ophthalmicus profundus, points of sufficient importance to render
a comparison between the two nerves at any rate a possible and
suggestive one. In each case the proximal portion of the nerves
in question connects together directly the ganglion of one seg-
mental nerve with that of the nerve next in front, while the
distal portion passes forward into the segment anterior to that
in which the main branches of the nerve are contained. The
early origin, the curiously straizht course, and the absence of
branches until close to their termination, are features common to
the two nerves, and ones in which they stand in marked contrast
to most other branches. The deep course of the profundus as
contrasted with the very superficial one of the buccal nerve may
perhaps be attributed to the great development of the eye: in
front of the orbit the profundus is a superficial nerve, and like
the buccal, is purely sensory in its distribution.
On the other hand, it must be noticed that, as already pointed
out, the evidence is distinctly in favour of the distal portion of
the profundus (beyond the ciliary ganglion) being a branch of the
third rather than of the fifth nerve. Another point of distinction
between them lies in the fact, that the former (the profundus)
is distributed to what is, morphologically, the dorsal surface, the
buccal to the ventral.
In the present paper we have purposely refrained from
| Op. cit., p. 202.
2 Op. cit., Pl. XIV, fig. 2 and fig. 15 a.
OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 499
attempting to determine the homologies between the nerves of
Scyllium and those of other vertebrates, preferring to wait
until by the study of the development of other types we are
enabled to bring forward positive evidence in support of our
determinations.
In conclusion, we would express the hope that, by working
out the development of the roots and branches of the cranial
nerves in a very typical vertebrate, and following these roots
and branches through their subsequent changes up to their adult
condition, we have rendered more practicable than has hitherto
been the case comparisons between the descriptions of embryos
and of the eorresponding adult animals, and have contributed
something towards the establishment upon a firm basis of
comparative neurology.
500 J. C. BLOOMFIELD AND A. G, BOURNE,
On the OccuRRENCE of CorpuscLEs in the Rep VascuLaRr
Fiurp of Cumropops. By J. E. Buomriz.p, B.A., and
A. G. Bourne.
Ir used to be (or we may even say that it is) an accepted
commonplace of zoological science, that the red vascular
fluid of the Cheetopoda is devoid of corpuscles. Certain
exceptions have been admitted, but they have been regarded
as exceptions. In reality they appear to be no exceptions
but the rule. Professor E. Ray Lankester (‘ Quart. Journ.
Mic. Soc., vol. xviii, 1878, p. 68) has demonstrated the
existence of colourless corpuscles in the red vascular fluid of
the earth-worm, and has described them as “small, oblong,
flattened, fusiform bodies, with clear, sharp outline, beyond
which occasionally appears a small quantity of ragged pro-
toplasm,” and considers them to be merely nuclei of the
cells forming the walls of the vessels which have become
“‘ free.”
In the above-mentioned paper there is a complete account
of what was hitherto known through the researches of M.
Ed. Claparéde and M. De Quatrefages, as to the existence
of similar corpuscles in the red vascular fluids of other
Chetopods.
Since the publication of this paper, Dr. Franz Vejdovsky
(* Beitrage fiir Vergleichenden Morphologie der Anneliden. 1.
Monographie der Enchytreiden.” Prag, 1879) has described
similar corpuscles in Criodrilus, and mentions them as occur-
ring in Tubifex, about which latter genus Dr. Vejdovsky
promises to say more on a future occasion. These cor-
puscles have then been hitherto observed in the following
genera :—Lumbricus, Criodrilus, and Tubifex, among the
Oligocheta; Ophelia, Cirrhatulus, Terebella, Staurocepha-
lus, and Syllidea, among the Polychaeta.
We are enabled to add to this list Eunice and Nereis, in
both of which genera we find similar corpuscles. ‘These
corpuscles are rendered evident by treating a portion of part
of the tissue which is well supplied by these vessels, e.g. a
muscular septum or parapodium, or even better, merely a
portion of one of the larger vessels removed to a slide with
two pairs of forceps, the blood being kept in it, with osmic
acid in l-per cent. solution, followed by picrocarmin, the
excess of the latter being removed by blotting-paper, and
the tissue washed first with water and afterwards with gly-
CORPUSCLES IN RED VASCULAR FLUID OF CHZTOPODS. 501]
cerin. To guard against error it is important to see the
corpuscles while actually within the walls of the vessels,
and to move them up and down by gentle pressure on the
coverslip to distinguish them from the nuclei of the cells of
the wall of the vessel itself. This method is the one applied
by Professor Lankester to the investigation of the red vas-
cular fluid of the earth-worm, and it seems exceedingly pro-
bable that in most Chetopoda when carefully applied, it
will yield the same result as it did in that case, viz. evidence
of the existence of corpuscles in the red vascular fluid.
The corpuscles occur either singly or in small masses. In
Eunice they are either round and average ;,),,th of an inch
in diameter, or are oblong with a long diameter of 3,',;th
of an inch. In Nereis the corpuscles are mostly round and
rather smaller, varying from 79'5th to 4;4,;th of an inch in
diameter.
502 VINCENT HARRIS.
PactntaAn Corpuscries in the PANcREAS and MESENTERIC
Guanps of the Cat. By Vincent Harris, M.D.,
Lond., Demonstrator of Practical Physiology at St.
Bartholomew’s Hospital.
a. In the Pancreas.—In examining some specimens of the
pancreas of a cat, from a part which was closely adherent to
the duodenum, I observed a large number of Pacinian cor-
puscles. In one small section no less than three were seen
grouped together, with here and there a solitary one; they
were cut in various ways by a transverse section of the tissue,
and so evidently lay with their long axes placed in various
directions. The largest number of the corpuscles was seen
near the outside of the sections, in the connective-tissue cap-
sule of the organ, but in one or two instances a solitary cor-
puscle appeared in the midst of the gland amongst the scanty
interlobular connective tissue. The difference in the size of
the bodies was very marked, some being twice as large as
others, but not any so large as those generally observed in
the mesentery proper.
As regards structure, they showed extremely well the
hyaline ground membranes lined with endothelium, but
here and there an appearance as though they were separated
from one another by an albuminous material in addition.
The average number of the ground membranes in a corpuscle
was about twenty-two.
B. In Lymphatic Glands.—In the mesenteric glands of
a cat examined in sections, I also noticed a large number
of Pacinian corpuscles. These again were found to be
situated to the outside of the sections, and were evidently
contained less in the gland itself than in the loose connective
tissue surrounding it. They presented the structure of the
ground membranes and of the central mass perfectly, and
the termination of the axis cylinder, closely invested with
large nuclei, was in most cases contained in a sheath filled
with a brownish material, which would not stain well with
logwood. This material was probably similar to that which
was observed between the capsules of the corpuscles in some
specimens of the pancreas.
The appearance of Pacinian corpuscles in the localities
mentioned above is most likely to be explained by the fact
that the tissues in which they were found are closely con-
nected with the mesentery, which in the cat is well known
to be abundantly supplied with such nerve endings. In
PACCINIAN CORPUSCLES IN THE CAT, 503
support of this supposition I may add that, in examining
some mesenteric lymphatic glands with the naked eye, I
observed that in the peritoneum surrounding at least two,
there was a large number of very small Pacinian corpuscles,
and that some might be traced almost to the gland capsule
itself. I cannot say definitely whether the mesentery proper
was well supplied with Pacinian corpuscles in the animals
from which the mesenteric gland and pancreas first men-
tioned were respectively obtained, but in the last instance
this was the case.
504 PROFESSOR E, RAY LANKESTER,
Limutus an Aracunip. By E. Ray Lanxester, M.A.,
F.R.S., Jodrell Professor of Zoology in University
College, London. (With Plates XXVIII and XXIX).
A. IntRopuction AND BiIBui0o- V. Hypothesis as to their
GRAPHY. mode of origin.
VI. Entosternite.
B. Comparison oF LIMULUS AND ;
ScoRPIO § c. Alimentary canal.
i § d. Vascular system.
§ a. Nervous system. § e. Generative glands.
§ 4. Skeleton. C. THe EvrypTerina as A CON-
I. Tergites. NECTING LINK.
II. Appendages. D. Review or opinions or MoDERN
ILI. Sternites. AUTHORITIES AS TO THE
IV. The common charac- AFFINITIES OF LIMULUS.
ters of the lamelligerous | E. Conctusions: LimuLus aAwnpD
appendages of Scorpio THE ANCESTRY OF TRa-
aud Limulus. CHEATE ARTHROPODA,
A. INTRODUCTION AND BIBLIOGRAPHY.
Tue prevailing opinion among zoologists at the present
day, with regard to the affinities of the King Crab, is that
it must be regarded as one of the Crustacea. Even when
this view is not fully accepted the King Crab is placed in a
special position of isolation and its relationship with Crus-
tacea strongly insisted upon, whilst more remote affinity
with the Arachnida is grudgingly admitted.
My friend Edouard Van Beneden, of Liége, is the only
zoologist who has definitely taken a divergent line, and has
frankly endorsed the instinctive perception of Straus Durk-
heim in declaring that Limulus is no Crustacean, but simply
and unreservedly an Arachnid. Ed. Van Beneden bases his
opinion upon embryological data. I have elsewhere ex-
pressed my full cuncurrence in that opinion, but the grounds
upon which my conclusion rests are not solely embryological
—they have reference to the structure of the adult Limulus
and Scorpion. In the following pages I hope to show that
Limulus is best understood as an aquatic scorpion, and the
Scorpion and its allies as terrestrial modifications of the
King Crab.
My views on this subject were formed some eight years
ago, and I have to acknowledge the kinduess of Mr. Car-
rington, F.L.S., of the Royal Westminster Aquarium, by
which I have been enabled to dissect and make histological
study of perfectly fresh specimens of Limulus sent to me in
the living state.
LIMULUS AN ARACHNID, 505
It is not desirable at the outset to follow the history of
the discussion relative to the zoological position of Limulus.
Those who desire to become acquainted with the most im-
portant contributions to the subject should consult the
memoirs of Anton Dohrn and A.S8. Packard, who have given
very ample references to the literature of the subject.
I shall here give in alphabetical order a list of the chief
works referred to in the following pages, the number at-
tached to an author’s name when cited, having reference to
the number in the present list. After I have put forward
the facts and inferences with reference to the structure and
affinities of Limulus which appear to me to be well-estab-
lished, I shall briefly review the various opinions which
have been advanced by recent writers of authority.
—
Special Memoirs.
. Dourn, Anton. “ Bau und Entwickelung der Arthropoden,” ‘ Jen-
, aische Zeitschrift,’ Bd. vi, 1871.
. Gecenzaur, Carl. “ Anatomische Untersuchung eines Limulus,”
, ‘ Abhandlungen der naturforschenden Gesellschaft in Halle,’ 1858.
. GkenacHer. “ Unters. uber das Sehorgan der Arthropoden,” 1879.
. Lanxuster, E. Ray.‘ Mobility of the Spermatozoa of Limulus,”
‘Quart. Journ. of Mier. Science,’ 1878.
. Mitwz-Epwarps, Alphonse. ‘Recherches sur |’Anatomie des
IAmules,” ‘ Annales des Sciences Naturelles,’ 5th series, Zoologie,
ol. xvii, 1873.
: Naywrorr, George. ‘‘ Nervous and Circulatory Systems in Myria-
y poda and Macrourous Arachnida,” ‘ Philos. Transactions of the
_* Royal Society,’ part 11, 1843.
_“"7, Owen, Richard. “Anatomy of the King Crab,” ‘Transactions of
8
9
ao wo wpm Fe
for)
the Linnzan Society of London,’ 18738.
. Pacxarn, A.S., Junr. “The Development of Limulus polyphemus,”
‘Memoirs of the Boston Society of Natural History,’ 1872.
. Pacxarp, A.S,Junr. “'‘The Anatomy, Histology, and Embryo-
logy of Limulus polyphemus,” ‘Anniversary Memoirs of the
Boston Society of Natural History, 1880.
10. Van Benepen, Edouard. “De la place qui les Limules doivent
occuper dans la classification des Arthropodes,” Société Entomo-
logique de Belgique, October, 1871 (translated in the ‘ Annals
and Mag. of Natural History,’ 1872).
11. Van per Horven. ‘Recherches sur )Histoire Naturelle et
P Anatomie des Limules,’ Leyden, 1838.
12. Watcot, C.D. “The Trilobite,” ‘ Bulletin of the Museum of
Comparative Zoology at Harvard College,’ vol. vii, April, 1881.
13. Woopwarp, Henry. “ A Monograph-of the British Fossil Mero-
stomata,” ‘ Paleontographical Society of London,’ 1866—1878.
Text-books of Zoology.
14, Ciavs, Carl. ‘ Grundziige der Zoologie,’ fourth edition, first volume,
third part, p. 638, 1880.
506 PROFESSOR E. RAY LANKESTER,.
15. GeGENBAUR, Carl. ‘Elements of Comparative Anatomy,’ English
translation, 1878, p. 230.
16. Huxtey, Thos. H. ‘The Anatomy of Invertebrated Animals,’
1877, p. 260 and p. 374.
17. Harcxen, Ernst. ‘Generelle Morphologie,’ vol. ii, p. xe.
18. Owen, Richard, ‘ Lectures on Invertebrate Animals,’ 1843, p. 181.
19. Straus DurKHEIM in Appendix to the sixth volume of the French
translation of Meckel’s ‘Comparative Anatomy,’ 1829.
Embryology of Arachnida.
20. Batrour, F. M. ‘ Notes on the Development of the Araneina,”
‘Quart. Journ. of Micr. Science,’ vol. xx, 1880.
21. Merscuntkorr, Elias. ‘“ Embryologie des Scorpions,” ‘ Zeitschrift
fiir Wiss. Zoologie,’ Bd. xxi, 1870.
As I am about to endorse the conclusion arrived at by an ©
eminent naturalist of the first half of this century, viz.
Straus Durkheim, it will be well to give here at once the
grounds upon which he based that conclusion.
Straus Durkheim maintained that Limulus should be
classified with the Arachnida, but the publication \of his
views on the subject appears never to have taken a very
definite or satisfactory form. In fact the only record of
Straus Durkheim’s teaching on this subject which I can
find is in the French translation of Meckel’s ‘General
Treatise on Comparative Anatomy.” MM. Riester and
Alph. Sanson carried out this translation, and added many
notes in the form of appendices to each volume. At the
end (p. 497) of the sixth volume, which bears the date
1829-1830, there is a note headed, “Sur l’appareil locomo-
teur passif des Arachnides,” which appears to be an abstract
of a memoir ‘On the Comparative Anatomy of the Arach-
nida, read to the Academy of Sciences, June Ist, 1829, but
never, I believe, published. M. Straus Durkheim com-
municated its contents to MM. Riester and Sanson. From
this note I submit a few extracts. The authors commence,
“La classe des Arachnides, dans laquelle M. Straus com-
prend le genre Limule, formant a lui-seul un ordre designé
sous le nom de GNATHOPODES, et dont il isole les Pycno-
GONIDES qu’il renvoie aux Crustacés, offre dans la disposi-
tion de son squelette et des muscles qui en meuvent les
diverses piéces, des particularités tellement tranchées qu’on
ne peut y méconnaitre un type different. C’est de ce
squelette que sont tirés les traits principaux propres a
characteriser la classe des arachnides en general, et qui
consiste dans la disposition des pattes rayonnant sur un
sternum commun, dans la présence @un sternum cartia-
gineux intérieur, dans Pabsence d’antennes.”
LIMULUS AN ARACHNID. 507
The Arachnida are then divided into three orders, “ les
pulmonaires, les branchiféres, et les trachéens,” but it is not
explained whether the term ‘‘ gnathopodes”’ is to be regarded
as simply a synonym of the order “ branchiféres.”
With regard to the internal sternum, the citation of the
views of M. Straus runs as follows:—‘‘ Dans Vinterieur du
thorax de tous les arachnides, a lexception peut-étre des
acarides dont la plupart des espéces sont trop petites pour
qu’on puisse les disséquer et connaitre leur organisation, on
trouve une piéce cartilagineuse diversement configurée
suivant les familles, et placée dans le thorax au-dessus du
sternum. Cette piéce, a laquelle convient le nom de sternum
interieur est maintenue librement par le moyen de plusieurs
muscles qui se soudent de différents points de sa surface sur
le bouclier, ou sur le sternum extérieur auquel ils se fixent.
Elle sert en outre de point d’insertion 4 un certain nombre
de muscles des pattes.”
Since the time when Straus Durkheim put forward these
views a mass of knowledge has accumulated which has
tended to throw light on the affinities of Limulus. Of most
importance has been the discovery of the complete form of
the body of the paleozoic scorpion-like Arthropods known
as the Eurypterina, and the quite recent (1873) thorough
investigation of the nervous system of Limulus, by Alphonse
Milne-Edwards, and further, the investigation of the de-
velopmental history of Scorpio, by Metschnikoff, and of
Limulus, by Dohrn and by Packard. The gradual growth
of the recognition of the Arachnidan affinities of Limulus
during the last twenty-five years is obvious enough, and yet
all systematic writers, and all who have especially discussed
the question, continue to classify Limulus among the Crus-
tacea whilst speculating as to the possible derivation of
the Arachnida from that form, or else place Limulus in a
distinct group, neither Crustacean nor Arachnidan.
I shall endeavour to show in the following pages that
there is a much closer agreement of parts between Limulus
and the Arachnida (especially Scorpio) than has been hitherto
admitted by any one writer, even by Straus himself.
It appears to me that the full extent of the agree-
ment between Limulus and the Arachnida has never yet
been stated, for whilst this or that observer has recognised
one set of facts he has overlooked or misinterpreted another,
and thus undervalued the indications of affinity between the
two forms which he had admitted to exist. That the King
Crab is as closely related to the Scorpion as is the Spider
VOL, XXI, —NEW SER, LL
508 PROFESSOR E, RAY LANKESTER,
has for years been an open secret, which has escaped notice
by something like fatality.
B. Comparison oF LimuLus AND Scorpio.
The Arachnid which comes nearest in structure to Limulus
is the Scorpion. In some few points the Spiders and, yet
again, the Phrynidz are more closely similar to Limulus
than isthat animal. I shall proceed, systematically, through
a comparison of the skeletal and chief internal organs of
Limulus with those of Scorpio, pointing out where other
genera of living Arachnida come into closer agreement with
the former than does the Scorpion.
§ a. NERVOUS SYSTEM.—As the view which may be
adopted in regard to the agreement or distinctness of appa-
rently corresponding parts in Limulus and Scorpio depends,
to a considerable extent, on the indications afforded by the
nervous system, it will be as well to proceed at once to
state what is now known with regard to that system in
both Limulus and Scorpio.
For a long time our knowledge of the nervous system of
Limulus was very defective, owing to the fact that only
badly preserved spirit-specimens had been dissected. Hence
it has been held by Van der Hoeven (11) and by Owen (7)
that the nerves which supply the first two pairs of appen-
dages take their origin from a nervous mass in front of the
cesophagus. Dohrn (1) and Huxley (16), on the other hand,
have stated that only the nerves to the first pair of appen-
dages are pre-cesophageal in origin. It was reserved for
M. Alphonse Milne-Edwards (5) to demonstrate by the dis-
section of perfectly fresh specimens of Limulus the true
arrangement of these parts. I am able, from my own dissec-
tion of a fresh specimen of the same animal, to confirm
M. Milne-Edward’s description, though I must say that such
confirmation is a mere formality, since the beautiful memoir
in which that author has published his results bears through-
out unmistakable evidence of care and accuracy.
With regard to the nervous system of Scorpio, we are not
in the same favourable position. No zoologist, so far as I
am aware, has studied the nervous system, or, indeed, any
of the viscera of Scorpio by the aid of fresh specimens, and
I cannot but expect that some very important modifications,
in accepted conclusions, may result from a renewed investi-
gation of the anatomy of that animal carried out upon freshly
killed individuals. Nor has the nervous system of the adult
Scorpion been studied by the aid of the microscope, in regard
to which deficiency we are in the same difficulty so far as
LIMULUS AN ARACHNID. 509
Limulus is concerned in spite of Packard’s recent work-in
that direction (9) ; in fact, the comparative anatomy of the
nervous system of Arthropoda generally has yet to be placed
on a firm histological basis, and until this is done we must
not attach a very great importance to the results of simple
dissection. With regard to the naked-eye appearance of
the nervous system of Scorpion, we have, however, the
exceedingly careful work of George Newport (6), which is
worthy of all confidence, and what is of more importance
we have certain embryological data furnished by the investi-
gations of Metschnikoff (21) and of Balfour (20). The
observations of the latter zoologist relate to the Araneina,
but may fairly be considered as confirmatory of those of
Metschnikoff.
The central nervous system of Limulus consists, according
to M. Alph. Milne-Edwards, (A) of a distinctly emarginated —
brain or cerebral mass which I have elsewhere proposed to
call the ARCHI-CEREBRUM,! and of two strands of nervous
tissue, which embrace the cesophagus and unite behind it, so
as to form (B) an oval aisOPHAGEAL COLLAR, being continued
backward from their point of union along the ventral surface
of the animal as (c) the ABDOMINAL CORD to a point some
distance in front of the anus. The limbs of the collar are
united by from three to eight transverse commissures in
front of their point of union with one another and behind
the esophagus. From the archi-cerebrum are given off five
nerves only, namely, those to the ocelli, to the compound
eyes, and to the frontal integument. From the esophageal
collar a great number of nerves radiate, including those to
the first as well as to all the other pediform appendages,
and also the nerves to the chilaria (or metathoracic sternites)
and to the genital operculum. We find a distinct nerve to
each appendage, and a number of large tegumentary nerves
also given off from the cesophageal collar. It is important to
note that the pair of nerves to the genital operculum is
derived from this region and not from the cord-like prolonga- »
tion of the united strands of the collar. It is also important _
to observe that at present we have no knowledge of the exist-
ence of distinct ganglia or enlarged masses of nerve-cells in
the esophageal collar, so that it is not possible to infer from
any such fact of strifcture how many ganglia corresponding
to an equal number of segments are represented by the
cesophageal collar. M. Alphonse Milne-Edwards, who holds
the ‘‘chilaria” to be the equivalents of the Scorpion’s “ pec-
1 This Journal, April, 1881. ‘On the Appendages and on the Nervous
System of Apus cancriformis,’
510 PROFESSOR E. RAY LANKESTER,
tiniform organs,” considers that eight pairs of ganglia are
thus represented, a pair for each of the walking legs, a pair
for the chilaria, and a pair for the genital operculum. The
4 chilaria appear to me (as explained below) to be simply
sternites,” and not related to the Scorpion’s “combs;” and
and I should therefore consider only seven pairs of segmen-
tal ganglia to be represented in the cesophageal collar. The
_ history of development is not yet quite definitely ascertained,
but it should decide this point, and should show, supposing
the views which I am about to advocate are correct, that
there is no ganglionic enlargement of the cord corresponding
to the “chilaria,” whilst the ganglonic enlargement from
which the genital operculum is innervated should at first be
more distinctly abdominal in position, and at a later period
become fused with the six ganglion-pairs corresponding to
the pediform appendages,
The third portion of the central nervous system of
Limulus distinguished as the ABDOMINAL CORD, stretches
from the cesophageal collar into the abdominal region, and
gives off no nerves over a space equalling half its total
length; it then enlarges and gives origin to a series of five
groups of nerves, of which the first four correspond to and
supply the four first pairs of branchial feet, whilst the fifth
supplies not only the fifth pair of branchial feet, but also the
preanal and perianal regions and the postanal spine. As
to the disposition of nerve-cells in this ahdominal cord we
have no information, that is to say, as to whether it is
possible anatomically to define separate ganglia in connec-
tion with the five groups of nerves in its hinder part, or in
any region in front of them.
A very important relation between the arteries of Limulus
and the main nerve trunks was first indicated by Owen (18),
but more fully elucidated by Alphonse Milne-Edwards. This
consists in the ensheathing of the cesophageal collar and of
the abdominal cord in an actual arterial trunk; not only
this but many of the larger nerves (those to the limbs) are
‘ ensheathed also by branches of the same arterial trunk.
M. Milne-Edwards has pointed out that this arrangement is
most nearly approached in Scorpio, and has recognised the
remarkable agreements between the agterial system of the
two animals—to which reference will be made further on—
though he nevertheless is led by other considerations which
are, I think, erroneous, to refuse to Limulus a position
among the Arachnida. ;
When we compare the nervous system of Scorpio, as far
as it has been made known by Newport and Metschnikoff,
*.
LIMULUS AN ARACHNID. 511
with that of Limulus we find portions precisely correspond-
ing to the three main regions above distinguished in the
latter animal. Anteriorly we have (a) a cerebral mass
supplying the central and marginal eyes with nerves, (B) a
large cesophageal collar, from which radiate the nerves to
the appendages and some other parts, and (c) an abdominal
cord which terminates in the fourth of the narrow preanal
segments of the body.
When we lock into details a little more closely we find
some very obvious differences between these regions as pre-
sented in the Scorpion on the one hand and in Limulus on
the other. But it must be remembered, in regard to these
differences, that we have no account of the Scorpion’s nerve-
centres derived from the dissection of fresh specimens, nor
of the actual arrangement of nerve-cells and nerve-fibres as
revealed by microscopic examination.
In the first place the brain and the esophageal collar of
Scorpio are more intimately fused with one another than
are the corresponding parts of Limulus. Moreover, the
esophageal collar is relatively more massive, and exhibits
but a small perforation for the passage of the very narrow
esophagus. Instead of being bridged over behind the ceso-
phagus by transverse commissures, as in Limulus, the two
halves of the collar appear to be flattened out here and
fused with one another. It is possible that a more accurate
knowledge of this region in Scorpio might show structure
representing the transverse commissures of Limulus.
A long tract of the most anterior portion of the abdo-
minal cord in Scorpio, as in Limulus, gives off no nerves.
But in accordance with the elongated form and well-
marked segmentation of the hinder region of the body, we
find that after this first tract there are, in Scorpio, seven
well-marked ganglia placed at intervals on the cord, the
most anterior of them sending off nerves to the third pair of
lung-sacs, but to nothing in front of this.
With regard to the actual origin of nerves, it has always
been stated that the first pair of appendages of Scorpio
receive each a nerve from the pre-cesophageal ganglion. If
this were absolutely the case it would mark a considerable
difference between Scorpio and Limulus. But as a matter
of fact mere inspection of Newport’s drawing is sufficient to
show that the nerves to the chelicerze of the Scorpion have
a lateral position embracing the true “ archi-cerebrum,”
which supplies the lateral and central eyes between them,
and whatever may be the result to be obtained in the future
by microscopic sections or study of fresh specimens, we have
512 PROFESSOR E. RAY LANKESTER,
the important embryological fact due to Metschnikoff (and
confirmed for other Arachnida by Balfour) that the nerve-
ganglion mass from which the nerve to the chelicera on each
side takes its origin is guite independent of the archi-cere-
brum, and in the embryo is placed behind the latter, and to
the side of the cesophagus right and left. This seems to me
sufficient to justify a complete assimilation of the two regions
in Scorpio and Limulus, the difference being merely that post-
embryonic fusion of the archi-cerebrum and lateral ganglia
has proceeded a little further in Scorpio than in Limulus.
From the collar, then,in Scorpio, as in Limulus, the
nerves to all six of the pediform appendages take their
origin. But the agreement extends even further than this,
for the nerves to that region of the Scorpion’s body which
corresponds with the genital operculum of Limulus also
proceed from the cesophageal collar. The attraction (if 1
may use the term) of nerve origins to the cesophageal collar
appears to have proceeded further in the Scorpion than in
Limulus, for, whereas, in Limulus, the first and remaining
four pairs of branchial feet are supplied from the abdominal
cord, in Scorpio those parts, which for reasons to be given
below, I consider to represent the first, second, and third of
the branchial feet of Limulus, all appear to receive their
nerves from the esophageal collar, so that it is not until
we come to the representatives of the fourth pair of bran-
chial feet of Limulus (viz. the third pair of lung-books, see
below) that we find in the Scorpion a nerve supply from
the abdominal cord. This phenomenon of the travelling
forward and concentration of nerve origins and their con-
nected ganglia is one sufficiently familiar in various groups
of animals. The fact of the dislocation in this way of the
nerve supply of the genital operculum of Limulus above
remarked on, receives illustration by the still further carry-
ing out of the same process in Scorpio.
The difference in the disposition of the nerve orgins (such
as it is) in regard to the hinder part of the abdominal cord
in the two animals receives its explanation from the differ-
ence of general form and segmentation of the hinder region
of the body which they respectively exhibit.
It appears, then, that there is when the most recent results
of anatomical and of embryological observation are taken
into consideration, no important difference between the
central nervous system of Limulus and of Scorpio, and more
especially it is to be noted for the purpose which we have
next in view, viz. that of comparing the skeleton and ap-
pendages of the two animals, that there is not a difference of
LIMULUS AN ARACHNID. 513
origin in the large nerves supplying the appendages, or the
genital or the respiratory region, which can forbid us from
unreservedly accepting as exactly representing one another,
parts, which on the ground of numerical sequence, appear to
reciprocally correspond.
§ 6. SKELETON.—I. Tergites, or Dorsal Sclerites.—It is
difficult to separate the description of one part of the skeleton
OC -.-/.....
eA rine es XIV to XVIIl
Anus
Fie. 1.—Outline of the tergal surface of Limulus polyphemus (drawn from the
object). The dotted lines correspond to the markings on the abdo-
minal carapace, which in the adult indicate what were separate segments
in the embryo. 4c’. Simple eyes (mesial). oc. Compound, or grouped
eyes (lateral). 2.4. Post-anal spine.
of Limulus and Scorpio from that of another, and in com-
514 PROFESSOR E, RAY LANKESTER.
mencing with the tergal elements, we must necessarily refer
simultaneously to the general disposition of the appendages.
Cephalothoracic tergites—In Limulus (woodcut, fig. 1),%
as in Scorpio (woodcut, fig. 2), the anterior region of the
body is covered in by a large sclerite, which is known as the
cephalothoracic plate or carapace.
ro =f S<48e4
oD
>
Fic. 2.—Outline of the tergal surface of a scorpion, Buthus Kochii (drawit
from the object). oc’. Simple eyes (mesial). oc. Grouped eyes (lateral).
P.A. Post-anal spine. The anus is on the sternal surface.
In Limulus its margins are produced and its posterior -
angles extended, so as to produce a form which differs from
1 It is necessary to state once for all that where not otherwise expressed
I always allude by the term Scorpio, or Scorpion, to the species Buthus
Kochii, of India, which happens to have been that studied by me. Other
species differ in trifling details from this.
LIMULUS AN ARACHNID. 515
that seen in the Scorpion, but in essential points there is
remarkable agreement. In both the carapace carries two
paired groups of eyes. Nearer the middle line is a single pair
of simple eyes (0c’), which in Scorpio have an almost central
position; more laterally placed (quite laterally in Scorpio)
is a group, on either side, of simple eyes (0c), which in
Limulus are so closely aggregated as to form what is often
called. “ a compound eye.” The compound eyes of Limulus
have, however, been shown by Grenacher (3) to differ very
much in structure from the compound eyes of either Crus-
tacea or Insects, to which they have usually been asssimi-
lated. They are more correctly interpreted—as the com-
parison with Scorpio would suggest—as an aggregation of
simple eyes. Such an aggregation (varying, according to
the genus, in number from two to five) we find in a less
compact form than in Limulus on the right and left side of
the Scorpion’s cephalothoracic tergite.
In both Limulus and Scorpio the cephalothoracie tergite
covers in an area corresponding to the six leg-like appen-
dages which are present in both animals, and may therefore
be considered as representing six coalesced tergites (1 to V1).
In Limulus the genital operculum which follows upon the
legs, and also the metathoracic sternites or chilaria which lie
between it and the bases of the last pair of legs, have been
by some morphologists regarded as also indicating segments
which should be reckoned to the cephalothorax, and accord-
ingly eight coalesced tergites have been supposed to con-
stitute the carapace of the King Crab, whilst only six can be
reckoned for the Scorpion. In reality, however, the chilaria
are not appendages at all, as is proved by their late appear-
ance in development (Packard, 8) and their form; they are
simply sternites corresponding to the pentagonal sternite
placed between the bases of the last pair of legs in Scorpio
(woodcut, fig. 5). As to the genital operculum of Limulus,
though in the adult it is in some measure adherent to the re-
gion of the cephalothorax, yet it has a tergal area correspond-
ing to it in the abdominal carapace, and in the embryonic
Limulus is clearly seen to belong to that region, and not to
the cephalothorax. The innervation of the genital operculum
from the esophageal nerve-collar has, as already pointed,
out, no weight as an argument in favour of the association of
that coalesced pair of appendages with the cephalothorax,
for on the very same grounds it would be necessary to asso-
ciate a large part of the middle region of the Scorpion’s
body (as far as and inclusive of the second pair of pulmonary
sacs) with the cephalothorax.
516 PROFESSOR E, RAY LANKESTER,
Abdominal tergites—Following upon the cephalothoracic
plate we have in the Scorpion seven wide band-like sternites,
to which succeed five narrow cylinders, the dorsal part of
each of which is tergite, and solidly fused with the ventral
half or sternite. In the last of these twelve segments is
placed the anus (in fig. 2 its position is marked, though it
is not seen on account of its ventral position), and beyond
the anus is the postanal spine or sting.
In Limulus (fig. 1), in place of the seven band-like and
five half-cylindrical tergites, we find one large chitinous
plate, which is known as the “ abdominal carapace.” In its
posterior region is placed the anus, and to it succeeds a post-
anal spine, sometimes, but erroneously, compared to the cylin-
drical segments of the Scorpion’s body. Clearly enough the
postanal spines in the two cases correspond to one another.
If there is correspondence between Limulus and Scorpio of
segment for segment and piece for piece throughout (as it
is the purpose of this essay to demonstrate), then in the
abdominal carapace of Limulus we must find the repre-
sentatives of the twelve segments, which in the Scorpion
exist between cephalothorax and anus. The embryonic
Limulus, as has been shown by Dohrn and Packard, ex-
hibits in this region of the body a series of separated seg-
ments, which fuse together as growth advances, and constitute
the one immovable abdominal carapace. In the adult the
indications of the former existence of these separate seg-
ments is more Obvious than has been supposed. In fig. 1
I have indicated by dotted lines the series of ridges, which
can be made out in the abdominal carapace of an adult
Limulus polyphemus, and which clearly mark off a number
of the original segments.
With regard to the general form of this region as com-
pared with the body of the Scorpion, it may be pointed out
that here, just as in the region of the cephalothorax, there is
an excessive development and exaggeration of the margin
of the dorsal integument, so that the central area marked
out in the figure is the real “ body” of the Limulus, and
the wide spreading lateral areas are only enormous excres-
scences of a relatively superficial character. It is not diffi-
,cult to find numerous parallels to these pleural develop-
ments in all groups of Arthropoda.
Returning to the examination of the actual number of
segments indicated in the abdominal carapace of the adult
Limulus, we find areas corresponding to the seven wide
tergites of the Scorpion marked in the drawing of Limulus
by the numbers vil to x111. Corresponding to these areas
LIMULUS AN ARACHNID, 517
are a series of marginal processes, the first corresponding to
the first area, is a mere angular process of the integument,
but the six which follow are in the form of movable spines.!
Corresponding also to the six segments which bear the
six spines (that is, to the six hinder segments of the seven
in question) are a series of pits in the axial region of the
tergum, a pair in each segment.
—+
Fig 3.
Fic. 3.—View of the abdominal carapace of Limulus polyphemus from
below, the soft sternal region and appendages of the anterior six
segments and the viscera having been removed.
The figures vi1 to x11 upon the drawing (drawn from the object) are placed
by the sides of the tergal entapophyses. The continuation of the same
series (XIII to XVIII) is placed upon the chitinized sternal surface
of the unsegmented region, which in Limulus represents the seventh
abdominal and the five cylindrical preeanal segments of the Scorpion.
These are deep invaginations of the integument forming
hollow processes, pushed as it were into the body cavity and
clothed internally with cartilage, the structure of which has
been described by Gegenbaur (2); they give attachment to
muscles and are well termed “ entapophyses”’ by Owen (7).
When we look in the abdominal carapace of Limulus for
representatives of the five cylindrical preanal segments of
the Scorpion, we find nothing but a broad smooth area
extending from the marking which indicates the hind
? These spines I have seen slowly moving, independently of one another,
in the living King Crab, indicating a separate musculature for each spine.
518 PROFESSOR E, RAY LANKESTER,
border of the thirteenth segment (seventh of the abdominal
series) to the soft membrane which forms the hinge of the
postanal spine.
In the embryo Limulus, however, this area is further seg-
mented. We do not find the five segments of the Scorpion,
but we find two of which (as segments) no indication is left
in the adult, and the foremost of these carries a movable
spine on each side like those in front of it.
The anterior margin of the segment or tract of the body
which carries the anus appears to be uniformly in Arthro-
poda, and in some other segmented animals, the part from
which new segments grow and become individualised, and
it is to this tract of the body including its pree- and post-
anal regions that the name “ telson” is applicable as, for
example, in the Lobster. It not unfrequently happens that
this segment-producing region does not produce the full
number of segments in given examples of an Arthropodous
class, which is characteristic of the majority or of the more
fully segmented members of the class. Thus, both in
Crustacea and Arachnida we find numerous forms with a
reduced number of abdominal segments. Usually, however,
as in the spiders, the embryo exhibits at some time of its
development the full complement of segments, the hinder-
most of which subsequently become obliterated by fusion or
atrophy. Limulus so far conforms to this plan as to show |
the segmental potentiality of its preanal area, but fails to
exhibit to the observer the full complement of segments even
as a temporary arrangement of its living substance.
Accordingly the whole area posterior to the ridge mark-
ing the posterior border of the thirteenth segment may
be regarded in Limulus as belonging to the “telson,” or
area of potential segmentation, a certain reservation being
observed in respect to the one or two minute segments
which appeared and disappeared in this region in the
embryo.
We may, when comparing this condition of things with
that exhibited by the Scorpion, either consider the telsonic
area and spine of Limulus as representing the five cylin-
drical segments and the sting of the Scorpion in an unseg-
mented state, or we may insist rather upon the actuality
than the protentiality, and identify the telson or fifth of the
cylindrical segments of the Scorpion (viz. that carrying the
anus), and the postanal spine with the telsonic area and
spine of Limulus, whilst regarding the four anterior cylin-
1 Note also the evanescent character of the three last segments of Thely-
phonus (fig. 12).
LIMULUS AN ARACHNID. 519
drical segments of the Scorpion as something over and above
and not developed in Limulus at all.
It seems, however, probable from the evidence of extinct
forms, as well as from the abortive segmentation of the
embryo, that Limulus is mo¢ derived from an ancestor in
which the telsonic area was as limited in its production of
segments as it is in Limulus itself, but on the contrary, that
the ancestor of Limulus had the full complement of seg-
ments (and possibly more) which is seen in Scorpio and the
Eurypterina. In that case the przanal area and spine of
Limulus would not merely be an area representing the five
cylindrical segments and sting of Scorpio in poéentzality,
but would be the actual representative of those segments
gradually reduced and fused in the course of an historic
process of change.
II. Appendages.—At each stage of the comparison between
Limulus and Scorpio, the proofs of the intimate affinity of
the two animals become more convincing, since we find that
the view which it is necessary to adopt in order to make
one set of structures agree closely in the two animals, is
precisely the view which it is necessary to adopt, when a
second set are considered, in order to make agreement
possible.
We have just dealt with the tergites and have found an
exact correspondence of piece for piece, with the exception
that four preeanal segments are suppressed or five fused in
Limulus which are discretely present in Scorpio. In order
to admit such an agreement of piece for piece as to tergites,
we have to reject the view that the chilaria and the genital
operculum represent segments belonging to the cephalo
thoracic tergite, for in that case the cephalothorax of
Scorpio would be a fusion of six, whilst that of Limulus
would be a fusion of eight pieces.
When we come to examine the sternites, we shall find
that the exclusion of the chilaria from the series of appen-
dages is exactly what is required in order to identify the
sternites of Limulus with those of Scorpio, and the removal
of the genital operculum of Limulus from the cephalo-
thorax makes its identity with the genital operculum of
Scorpio even more obvious than it would otherwise be.
The six pairs of appendages of the cephalothorax of
Limulus may be compared one by one with the six pairs of
Scorpio.
Cephalothoracic appendage, No. I—We have already
disposed of the obstacle which has been always raised
hitherto when the chelicere of the Scorpion have been
520 PROFESSOR E, RAY LANKESTER,.
Fic. 4.—Cephalothoracic appendages of Scorpio (left), and of Limulus
(right), drawn from the object. cov, coxa. s¢e, Sternocoxal process of
the coxa. epe. Epicoxite. ea’. Exite of the coxa of the sixth ap-
pendage of Limulus. en’. Endite of the fourth segment of the same
limb. a, 4, c, d. Endites and exites of the fifth segment of same.
en®, Endite of the sixth segment of the same.
LIMULUS AN ARACHNID. 521
assimilated to the chelicere or first pair of limbs of Limulus.
Instead of there being a difference as to innervation we
have seen that there is a real identity.
In Limulus, each of the first pair of appendages is a
short pair of nippers (woodcut, fig. 4, 1, right) composed of
three sclerites; at the base of the two appendages and
between them and the mouth is placed an ovate sternite, the
camerostome or upper lip. (Plate XXVIII, fig. 4).
In Scorpio (woodcut, fig. 4, 1 left) a similarly small pair
of appendages is found similarly composed of three sclerites,
and similarly overhanging an oval “ camerostome.”
Ceph. thor. app., No. II.—In this and the following leg-
like appendages of Limulus six chief sclerites are developed,
the basal one or “coxa” being much enlarged, and its in-
terior border produced into a well-marked process provided
with tooth-like hairs. The arrangement of the limbs around
the mouth and the central sternite which follows it (pmsé¢
in Pl. XXVIII, fig. 4), is such that the processes of the
coxze of all ten limbs act together as manducatory organs.
The process of the coxa may be called “the sterno-coxal
process ”’ (ste. in the woodcut, fig. 4). The second cephalo-
thoracic appendage in the female Limulus polyphemus is like
the third, fourth, and fifth, a chela—that is to say, the penulti-
mate sclerite is produced so as to form with the last sclerite
a pair of nippers. In the male this is not the case, the
second pair of appendages being thicker and heavier than
in the female, and the penultimate joint not prolonged. The
form of appendage seen in the male L. polyphemus in this
position is similar to appendages seen in other Arachnida
than Scorpio, viz. Thelyphonus (woodcut, fig. 12).
The second pair of appendages in the Scorpion is like
that of the female Limulus, but relatively larger. It con-
sists of six sclerites as in Limulus, and has a sterno-coxal
process on its coxa, which acts with its fellow of the opposite
side as a Jaw (woodcut, fig 4, 11).
Cephalo-thoracic appendage, No. III.—1n Limulus poly-
phemus this has, in both sexes, the same form as has the
second appendage in the female. It is similarly composed
of six sclerites, but in addition to these we find a distinct
movable sclerite developed on the median border of the coxa.
This sclerite may be termed the “ epicoxite”’ (woodcut,
fig. 4, 111, epe., right). The epicoxite is a remarkable
feature, and is not easily paralleled among Arthropoda.
The basal “ endite ” of the limbs of the Crustacean Apus is
similar to it, and perhaps derived from a common ancestral
origin.
522 PROFESSOR E. RAY LANKESTER.
In Scorpio the third cephalothoracic appendage is in the
form of a walking leg, and as such has seven sclerites. It
is a remarkable fact that in Limulus the sixth cephalo-
thoracic appendage, which is non-chelate, also presents
seven axial sclerites (woodcut, fig. 4, v1, right), so that the
Scorpion’s ambulatory limbs do not depart from the possi-
bilities of Limulus in developing axial sclerites beyond the
number six. It isalsoimportant to notice in this connection
that the Arachnida exhibit a great variability in the number
of joints present in their legs. 'Thelyphonus develops a four-
jointed “tarsus” at the end of the five proximal segments
of its ambulatory limbs (woodcut, fig. 12), whilst Galeodes
presents ‘a curious increase in the number of segments in
the proximal region of its hinder limbs (woodcut, fig. 10).
The most important feature in which the third and sub-
sequent cephalothoracic limbs of Scorpio resemble those of
Limulus is in the great development of the coxe. The
sterno-coxal process is present on the third and fourth
cephalothoracic appendages, and is even larger relatively than
in Limulus. In the third and fourth limbs it is free, overlying
a very soft minute sternal region belowthe mouth, and playing
with its fellow of the opposite side the part of an ingestive
organ for the mouth. The narrow cleft between the opposed
sterno-coxal processes probably acts by capillary attraction
in the taking up of such food as the blood of other animals.
The coxe of the fifth and sixth appendages of Scorpio
have, on the other hand, no free sterno-coxal process.
The great enlargement of the coxe of these four pairs of
appendages, and their encroachment upon the median area,
is accompanied by, and related to, the suppression of any
representative of the sternal sclerite (pmst., fig. 4,
Pl. XXVIII) which is present in Limulus. The coxe of
the third pair and of the fourth pair meet one another in
the middle ventral line, but are separated by soft membrane.
The cox of the fifth and sixth pairs do not meet their
fellows in the middle line, but are kept apart by the wedge-
shaped extremity of a sternite (met. in woodcut, fig. 8).
They differ from the coxze of the third and fourth pairs in that
the fifth is adherent to the sixth (woodcut, fig. 4, v, v1, left.)
The base of the third appendage in Scorpio exhibits a
development internal to the sterno-coxal process, which
corresponds to, and probably represents, the ‘‘ epicoxite ” of
Limulus. This is in the form of a movable plate (woodcut,
fig. 4, 111, epe., left), which presents parallel ridges on its
surface.
Cephalothoracic appendage, No. IV.—Appendage No. iv
LIMULUS AN ARACHNID. 523
in Limulus closely resembles No. 111. As in No. It, an
epicoxite is present.
The corresponding appendage of Scorpio has been already
mentioned. It has seven joints and a large sterno-coxal
process, but no epicoxite, such as occurs in the limb next in
front of it.
Cephalothoracic appendage, No. V.—In Limulus this
resembles Nos. 111 and 1Vv, like them having an epicoxite.
In Scorpio, No. v, is a seven-jointed ambulatory limb,
with large coxa fused to the coxa of the next following
appendage, but devoid of sterno-coxal process.
Cephalothoracic appendage, No. VI.—In Limulus this is
the characteristic digging limb, unlike in the special modifica-
tion of its parts and their remarkable function (for which
see the citations of Lockwood and of Lloyd in ‘ Owen’s
Memoir,’ No. 7) any other arthropod appendage.
In structure it is remarkable for exhibiting the feature of
secondary movable arthrites diverging from the axis of the
limb, unusual in Arthropoda other than the Crustacea. Seven
axial sclerites or segments can be distinguished, the coxa
being large, as in the other limbs, but devoid of an epicoxite.
On the other hand, whilst the “ endite ” is thus absent, an
“‘exite”’ is developed in the form of a flattened elongated
piece articulated to the external border of the coxa (wood-
cut fig. 4, vi ex’ right).
The second and third segments of the axis are devoid of
apophyses, but the fourth bears a large spine-like articulated
endite. The fifth joint of the axis carries four flattened
apophyses (endites and exites), which are articulated and
capable of active movement. ‘The sixth joint bears one arti-
culated endite, and, further, the short terminal seventh or
ultimate segment of the axis, which is relatively much
longer in newly hatched individuals than in the adult.
The sixth cephalothoracic appendage in Scorpio is quite
similar to the three preceding walking legs. Its large coxa
is fused to that of the fifth appendage of the same side. The
spinous outgrowths on the sixth and seventh segments of
this and the other legs are in character somewhat similar to
the more highly developed apophyses of the digging limb of
Limulus.
The seventh pair of appendages or genital operculum.—In
Limulus lying between the bases of the sixth pair of cepha-
lothoracic appendages is a pair of sclerites, the chilaria of
Owen, actually the metathoracic division of the sternum
(woodcut fig. 5,s¢. right), which belongs to the segment carry-
ing the sixth pair of appendages. Precisely similar in position
VoL, XXI,—NEW SER, MM
524 PROFESSOR E. RAY LANKESTER.
in Scorpio is a pentagonal! sclerite divided into a right and
a left half by a median groove (woodcut fig. 5, s¢ left upper
figure). This is, in like manner, the metathoracic sternite,
of which more will be said below.
Fic. 5.—The seventh (op) and eighth (ga) pairs of appendages of Scorpio
(left) and Limulus (right), together with the thoracic metasternites
(st of the upper figures), and sternites of the eighth segment (s¢ of
the lower figures). The anterior face of the appendages is shown
Drawn from the object.
Following in Limulus as in Scorpio upon the metathoracic
sternite, is a lid-like plate, the hinge of which is transverse
to the long axis of the body, and on the inner face of which
are placed, both in Scorpio and in Limulus, the genital
apertures, male or female, as the case may be (woodcut fig. 6,
vil, right Limulus, left Scorpio).
The history of development in Limulus shows that this
genital operculum starts as two independent processes of
the body, which are to be regarded as the appendages of the
seventh segment. The operculum retains throughout life
evidence of its double origin, and closely resembles in form
the five succeeding pairs of appendages which carry the
respiratory lamelle.
In Scorpio, on the other hand, the genital operculum is
relatively of very small size, as seen in figs. 5 and 8 go; in
fig. 6, it and the following appendages are drawn on an
enlarged scale for the purpose of comparison with the corre-
sponding parts in Limulus. Very little trace of having been
formed by the union of two lateral appendages is exhibited
by the genital operculum of Scorpio. At the same time its
1 Pentagonal in the subgenus Buthus, from which my drawings and
notes are taken, but more triangular and reduced in size in the subgenus
Androctonus.
LIMULUS AN ARACHNID. 525
Fic. 6.—The seventh, eighth, and ninth pairs of appendages of Scorpio
(left) and Limulus (right). The posterior face of the appendages is
shown. gp. Genital pore. s¢g. Parabranchial muscular stigmata
(tendons of the thoraco-branchial muscles) of Limulus. eps. Epistig-
matic sclerites of same. Drawn from specimens.
526 PROFESSOR E. RAY LANKESTER,.
Fa,
Fic. 7.—The tenth, eleventh, and twelfth pairs of appendages of Scorpio
(left), and of Limulus (right). The posterior face of the appendages
is shown. stg. Parabranchial stigmata of Limulus. eps¢. Epistig-
matic sclerites. /'. Mediad, or first lamella of the lamelligerous
appendages. /130. External, or one hundred and thirtieth lamella of
the same in Scorpio. /150. External, or one hundred and fiftieth
lamella of the same in Limulus. Draw from specimens. It is important
to note that in these and other figures the lung-books of the Scorpion
are represented as entirely freed from the delicate pulmonary sac which
invests them.
LIMULUS AN ARACHNID. 5a
bifid margin speaks of such an origin, and, as a matter of
fact, such appears to be its embryological history.
I shall here quote a passage from ‘ Balfour’s Embryology,’
recounting Metschnikoff’s observations upon the existence
of rudiments of appendages in the segments of the Scorpion’s
body following upon the cephalothorax with its six pairs of
limbs. The observations have great importance, not only in
reference to the genital operculum but also in regard to the
pulmonary sacs and their ‘branchial books” which are
found in succeeding segments.
Balfour says, “‘ Rudimentary appendages appear on the
six segments behind the ambulatory legs. . . . They persist
only on the second segment, where they appear to form the
comb-like organs or pectines. The last abdominal segment,
i.e. that next the tail, is without provisional appendages.
The embryonic tail is divided into six segments, including
the telson. The lungs are formed by paired invaginations,
the walls of which subsequently become plicated, on the
four last segments, which bear rudimentary limbs, and
simultaneously with the disappearance of the rudimentary
limbs ” (‘ Comp. Embryology,’ vol. i, p. 359).
Hence it appears that, in Scorpio, in front of the comb-like
organs, that is to say, in the position subsequently occupied by
the genital operculum, there is in the embryo, as in that of
Limulus, a pair of rudimentary appendages. We know that in
Limulus these grow together to form the genital operculum.
It is in the very highest degree probable that the same history
obtains for the similarly related genital operculum of Scorpio.
In discussing the tergites, it has already been pointed out
that the genital operculum corresponds to a separate band-
like tergite in Scorpio (v11, in woodcut, fig. 2), and to an
emarginated area on the anterior border of the abdominal
carapace of Limulus (vir, in woodcut, fig. 1), which is more
distinctly marked in the embryo.
The eighth pair of appendages.—In Scorpio we find, on the
ventral surface corresponding with the eighth tergite (six ter-
gites being reckoned to the cephalothorax )a pair of appendages
carrying fine lamellz set like the teeth of a comb along the in-
ferior margin (woodcuts fig. 5 ga, left, and fig. 6 vi1t, left ; see
also Plate XXVIII). They are developed from the second
pair of rudimentary abdominal appendages of the embryo.
In Limulus, in the corresponding position, we find a pair
of appendages, the first of a series of five pairs (woodcuts fig. 5
g@, right, and fig. 6 vit, right). The appendages of the two
sides, as in the case of the genital operculum, do not diverge
from one another but are directed towards one another and
528 PROFESSOR E, RAY LANKESTER.
united across the middle line by a soft plate-like fold of the
sternal integument ; the result being that a plate-like body is
formed from two originally distinct right and left appendages.
On the under surface of each of the combined appendages
a series of very delicate lamelle is found corresponding to
the lamelliform teeth of the Scorpion’s comb-like organs.
Ninth, tenth, eleventh, and twelfth appendages.—In
Limulus, corresponding to the tergal areas marked Ix, x, x1,
XII, we find a series of pairs of appendages precisely similar
to that belonging to the eighth segment.
In Scorpio it will be remembered that in the embryo
rudimentary appendages appear corresponding to the first
six abdominal segments, or the seventh, eighth, ninth, tenth,
eleventh, and twelfth of the whole body. Of these the first
pair we have seen, become in all probability the genital oper-
culum ; the second pair are known to become the ‘‘ pectines ;””
the pairs on the ninth, tenth, eleventh, and twelfth segments
disappear, as the lung sacs on those segments develop by a
process of invagination.
They disappear, but only from view. It has not been
shown by actual observation, but it cannot well be doubted,
that these rudimentary appendages sink within the lung-
invaginations, and become the lamelligerous appendages
which are found in them in the adult Scorpion.
The four pairs of stigmata on the ventral surface of the
ninth, tenth, eleventh, and twelfth segments of the Scor-
pion’s body (woodcut, fig. 8) lead into sacs, each of whch con-
tains, concealed within it, an appendage consisting of an axis
bearing a series of delicate lamellae (woodcuts, figs. 6 and
eX S, Royce, Tete).
Each of these concealed appendages is strictly comparable
in structure to one of the comb-like organs of the eighth
segment, the axis corresponding to the axis, and the delicate
lamellz to the teeth of the comb.
Thus, then, we find five pairs of lamelligerous appendages
on the five segments of the Scorpion’s body numbered 8, 9,
10, 11, 12, of which the first pair is external, and accordingly
modified, whilst the next four are sunk below the surface,
and accordingly modified. In Limulus, on the exactly cor-
responding segments, namely, those numbered 8, 9, 10, 11,
12, we find five pairs of lamelligerous appendages, but these
are all external, and all alike modified for the purposes of
aquatic respiration.1
! Latreille, though holding the Limuli to be Crustacea, and not Arach-
niaa, was the first to insist on the branchia-like character of the Scorpion’s
lung-books
LIMULUS AN ARACHNID. 529
Furthermore, it is important to notice that in Scorpio
neither in the embryo nor at any other time does the seventh
abdominal segment (thirteenth of the whole series) carry a
pair of appendages, nor do any of the subsequent cylindrical
segments. Similarly in Limulus no appendages or rudi-
ments of appendages are to be detected after the last pair
of lamelligerous organs—the twelfth of the whole series.
The segmented region, devoid of appendages in the
Scorpion, is represented by an unsegmented region devoid
of appendages in the King Crab.
Before entering into a more minute comparison of the
lamelligerous appendages of the Scorpion with those of
Limulus, with the object of establishing the identity of
origin of the two series by the detection of agreement
between them in details of structure, it will be most con-
venient to examine another series of skeletal elements,
namely, the sternites.
III. Sternites.—In Limulus, in the cephalo-thoracic region,
we find that the integument of the sternal area, though to a
large extent soft and devoid of hard chitinous plates, yet
presents here and there well-marked sclerites. On the
sub-frontal area, a small discoidal piece, the sub-frontal
sclerite is found (Pl. XXVIII, fig. 4, sf). Between the
mouth and the bases of the first pair of appendages a much
more important sclerite occurs, to which the term used by
Latreille for the similarly placed sclerite in Arachnida, viz.
(camerostome), may be used.
In the Scorpion (fig. 8, in front of the mouth to which the
line m points) a similar tubercular sclerite is found. There
is advantage in not merely designating this piece “ labrum,”
since there is but little ground for holding it to be equivalent
either to the labrum of Insecta or to that of Crustacea.
In the Spider Mygale (fig. 9) and in Galeodes (figs. 10
and 11, cam), this same piece is observed, attaining a remark-
able development in the latter.
When we come to the region behind the mouth, we find
in Limulus a large median sclerite extending from the
pharynx backward. It lies between the bases of the third,
fourth, fifth, and sixth pairs of cephalothoracic appendages.
On account of its position, it may be termed the thoracic
promeso-sternite (Pl. XXVIII, fig. 4, pmst), since it appears
to represent elements which, in other Arachnida, are marked
off as distinct prosternite and mesosternite.
In Scorpio we find nothing corresponding to this piece. By
the enlargement and mesiad production of the coxe of the
four hinder cephalothoracic appendages it has been as it were
530 _
Fic.
Fic.
PROFESSOR E, RAY LANKESTER,
8 (A).—Ventral aspect of a scorpion (Buthus Kochit), with the terminal
segments omitted. Drawn from the object. 1 to v1. The cephalo-
thoracic appendages. 11. Points to the sterno-coxal process of the
great chele, wr. To the sterno-coxal process of the first walking
leg. Iv. To the sterno-coxal process of the second walking leg.
met. Thoracic metasternite. vil go. The genital operculum. vut p.
The pectines, or eighth pair of appendages. z. Sternite of the eighth
segment. IX stg, x stg, X1 stg, x11 stg. Stigmata leading into the
pulmonary sacs, containing the appendages of the ninth, tenth, eleventh,
and twelfth segments. y. Sternite of the thirteenth segment devoid
of appendages. m. Mouth, in front of which is seen the camero-
stome.
9 (8).— Ventral aspect of a bird’s nest spider (Mygale sp), the hairs
removed. Drawn from the object. 1 to vi. Cephalothoracic appen-
dages. mM. Mouth, in front of which is seen the camerostome. pro.
Thoracic prosternite. mes. Thoracic mesosternite. s¢g. The apertures
of the two pulmonary sacs of the left side. gz. Genital aperture.
an. Anus.
obliterated. A similar obliteration has taken place in Galeodes
(fig. 10), but in Thelyphonus (fig. 12), a triangular sternite
(st¢’) is found (though erroneously omitted in the figure given
in the last edition of Cuvier’s ‘ Regne Animal’) in front of the
coxe of the fourth pair of cephalothoracic appendages.
The Arachnids, which come nearest to Limulus in the
LIMULUS AN ARACHNID. 53]
Fic. 10 and 11.—Ventral and dorsal aspect of Galeodes sp. (from the
object). 1 to vi. The cephalothoracic appendages. 7. Thoracic
right tracheal aperture. /?, /°. Abdominal tracheal apertures. ge:
Genital aperture. s¢. Sternal surface. a. Anus. cam. Camerostome.
ct. Cephalothoracic tergite. 7¢'. Prothoracic portion of the cephalo-
thoracic tergite. #. Separate mesothoracic tergite. 2, Separate
metathoracic tergite.
character of this portion of the sternal area, are the Spiders.
In Mygale (M. avicularia) the coxe of the five hinder
cephalothoracic pairs of appendages are arranged around a
large oval sternite (fig. 9), which is divided into two portions,
an anterior small prosternite (pro) and a larger mesosternite
(mes). This double piece appears to correspond to the
sternite of Limulus, marked pmsé in fig. 4, Pl. XXVIII.
It is not a little remarkable that, in astructural feature
observed in Limulus and zo# repeated in Scorpio nor in any
Crustacean or Insect, the closest parallel should be found in
another Arachnid; it is remarkable because it tends still
further to determine the association of Limulus with the
Arachnida in classification rather than with any other group.
Behind the thoracic promesosternite of Limulus, separated
from it by soft integument aud posterior to the coxz of the
PROFESSOR E. RAY LANKESTER,
Fic.
Fic.
Fic.
an -
12 (a).—Ventral aspect of Thelyphonus (from the object). 1 to vi.
Cephalothoracie appendages ; the first, which is concealed by the coxa
of the second, is represented as removed from its attachment. sfc.
Sterno-coxal process of the coxa of the left second appendage. sf}.
Thoracic prosternite. s¢?. Thoracic metasternite. vi to xvil1. Seg-
ments of the abdomen. J, 7. Apertures of the right lung sacs in the
ninth and tenth segments. msg. Muscular stigmata on the sternites
of the tenth, eleventh, twelfth, thirteenth, and fourteenth segments.
an, Anus.
13 (B).—Dorsal aspect of the abdominal segments of the same. _—p.
Muscular pits corresponding to the entapophyses of Limulus. paf.
The jointed postanal filament.
14 (c).—Abdominal segments of the same, with the terga and viscera
dissected away (after Blanchard). . Nerve cord. zg. Abdominal
nerve ganglion. J, 2. Pulmonary sacs in the ninth and tenth seg-
ments. m,_m,m,m. Muscles attached to muscular stigmata of the
four following segments. az. Anus. pa/. Postanal filament.
sixth pair of cephalothoracic limbs, we find a pair of closely
opposed upstanding sclerites, the chilaria of Owen (mets¢
1A
XXVIII, fig. 4, and woodcut, fig. 4). The late develop-
ment of these pieces, as determined by Packard, as well as
their position, leaves no doubt that they are not to be re-
garded, as is supposed by some, as rudimentary appendages.
They are a paired development of the metathoracic sternal
area and may be designated metasternites.
LIMULUS AN ARACHNID, 533
They have no representative in Mygale (fig. 9), but here
Scorpio returns to its allegiance and exhibits a well-developed
sclerite exactly corresponding to them. The pentagonal
sclerite wedged between the coxe of the last pair of cephalo-
thoracic limbs in Scorpio (woodcut, fig. 8, met) clearly
enough agrees in position precisely with the chilaria of
Limulus (see also woodcut, fig. 5). It is true that the form
of the pentagonal metasternite of Scorpio differs from that of
the two little tubercles of Limulus, but the exclusion from
the functions of the mouth of the former sufficiently accounts
for the difference.
In Thelyphonus (woodcut, fig. 12, s¢.”) a triangular meta-
sternite corresponding in position to that of Scorpio is found.
It is exceedingly astonishing that so careful an observer
as M. Alphonse Milne-Edwards should have suggested, as
he has done, that the “chilaria” of Limulus correspond to
the “‘ pectines ”’ of the Scorpion, since the former are in front
of and the latter are behind the genital operculum. When the
possibility of such homologies is entertained, it is but a natural
consequence that the complete series of agreements of segment
for segment and appendage for appendage which obtains be-
tween Limulus and Scorpio, should be entirely overlooked.
When we pass to the abdominal segments we find a very
considerable difference between Limulus and Scorpio in the
development of sternites.
The sternal integument of the region at the base of the
genital operculum and the gill-bearing appendages, is almost
entirely soft and free from sclerites in Limulus. In Scorpio,
on the other hand, whilst the sternal region around the
genital operculum is soft, a well-developed sternite (woodcut ,
fig. 8 z) is found supporting the pectiniform appendages ;
and for each of the five following segments a broad band-
like sternal sclerite is developed. The four anterior of these
are perforated, each by a pair of slit-like apertures leading
into four pairs of recesses, in each of which a lamelligerous
appendage is sunk. The fifth is imperforate, and bears no
appendage. The segments of the so-called ‘ tail” which
follow present a complete chitinisation of the integument, so
that the sternites of each segment is confluent with the tergite.
When we examine the sternal area of the segments of
Limulus which carry lamelligerous appendages, we find that
although the integument is mostly soft and flexible, yet
there are small sclerites present, and, in fact, stigmata or
apertures leading into pits corresponding to the stigmata of
the pulmonary sacs of Scorpio.
These parabranchial stigmata of Limulus have hitherto
5384 PROFESSOR E. RAY LANKESTER.
escaped observation.! They are found on the posterior face
of the median sternal elevation or lobe which unites the two
lateral elements or appendages which go to form one of the
double lamelligerous organs of that animal (Plate XXVIII,
fig. 10 stg, and woodcuts, figs. 6 and 7 stg). The lips of the
stigma are chitinised, and the opening leads into a funnel-like
cavity with chitinised walls. The sternal integument further
shows one or two small sclerites, the ‘‘ epistigmatic sclerites ”
(epst), by the side of the stigma. These stigmata occur in
the position mentioned, not only at the bases of the appen-
dages of the four segments corresponding to those which
carry the pulmonary stigmata in the Scorpion, namely, the
ninth, tenth, eleventh, and twelfth, but also at the base of
the appendages of the eighth segment, which represent the
pectines of the Scorpion, and at the base of the genital oper-
culum. They are connected with the attachment of a series
of powerful muscles, the thoraco-branchials, which, taking
their origin in the thorax, are inserted into the integument
right and left at the base of each of the six pairs of abdo-
minal appendages. The function of these muscles is clearly
enough to agitate this series of plate-like organs, either for
the purpose of respiration or fur that of locomotion, probably
for both simultaneously.
The fact that the insertion of a muscle into the integu-
ment of Limulus is connected with a “‘ cupping ” of the area
of attachment is remarkable but not without parallel. The
series of dorsal entapophyses have a precisely similar signi-
ficance, and in other Arachnida, e.g. Thelyphonus (fig. 12
msg fig. 13 p, and fig. 14 m), we find an identical
arrangement on both ventral and dorsal surface, the stig-
mata being, however, much shallower than in Limulus.
I am not aware of the occurrence of such “ muscular
stigmata ”’ in any other Arthropoda than the Arachnida, at
any rate, of stigmata comparable to those of Limulus.
Usually the tendons of muscles are in Arthropoda formed
by solid fibrous extensions of the subepidermic layers of
the integument.
The tendons or processes connected with the parabranchial
stigmata, and with the dorsal entapophyses of Limulus, are by
no means entirely formed by the invaginated epidermis and its
chitinous product. The tissue below the epidermis is deve-
loped in a very special manner, and forms part of an endo-
skeleton which in the thoracic region gives rise to a very
remarkable internal sternum or entosternite. The struc-
1 Tconimunicated an account of their occurrence and probable signi-
ficance to the Royal Society on May 26th, 1881.
LIMULUS AN ARACHNID. 535
ture of this deep skeletal tissue has been investigated by
Gegenbaur, who has shown that it may have the form
either of a fibrous or of a more distinctly cartilaginous
modification of the connective tissue into which it gradu-
ally passes, and from which, on the other hand, is developed
in other regions a series of vascular channels constituting
the capillaries, veins, and arteries. On the present occasion
I do not propose to enter into histological details with
regard to Limulus, but I may just mention that whilst the
hollow entapophyses are invested on their visceral surface
by a richly developed cartilaginous modification of the con-
nective substance, with a well developed capsular arrange-
ment of the intercellular substance, the funnel-like invagi-
nations connected with the parabranchial stigmata are
clothed and continued by a fibrous tissue not unlike the
tendon of Vertebrata. The same tendon-like tissue also
forms the entosternite.
In Plate XXVIII, fig. 11, the internal connection of the
pair of parabranchial stigmata of a lamelligerous appendage-
pair of Limulus is drawn. The integument has been dis-
sected away from the whole of the anterior face of the
appendages and their uniting sternal bridge, so as to show
the inner aspect of the integument of the posterior face.
The pouch-like character of the invaginations into which
the stigmata lead and the attachment of the thoraco-
branchial muscle is thus exhibited. In fig. 18, PI.
XXVIII, one of the funnel-like tendons, consisting inter-
nally of chitin borne on epidermis, and externally of fibrous
tissue, is shown in an isolated condition. It is possible to
introduce a probe into the funnel to the depth of an inch,
the axial cavity of invagination extending to that distance.
The funnel-like pouch of Limulus thus constituted, I con-
sider to be the homologue (that is, the genetic representa-
tive or homogen) of the pulmonary sac of Scorpion.
It will now be convenient to give, in a tabular form, a sum-
mary of the view which has been set forth in the preceding
pages. Having thus exposed what I conceive to be the legiti-
mate conception of the morphological relations of Limulus
and Scorpio, I shall endeavour to justify, by a closer
examination, the identification (which forms an essential
part of it) of the pectines of the Scorpion and its four
pairs of book-like organs sunk in recesses of the integu-
ment with the five pairs of lamelligerous appendages of
Limulus.
(The tabular statement is given on the next page.)
5 36 PROFESSOR E. RAY LANKESTER,
‘ LIMULUS.
3
om Tergites. Sternites. Appendages.
mT Camerostome (small/Small chele.
tubercular _ sclerite)
in front of the mouth.
2g Chel
3
The fused pro- and|Chele.
—| Cephalothoracie carapace | mesothoracic stern-
4 ites (a narrow elong-
with central and peri-
5 | pheral eyes.
7 |Narrow emarginate area
at the anterior border
of the abdominal cara-
pace. No dorsal pits.
8 |1st pair of lateral spines.
Ist. pair of dorsal pits
and entapophyses.
9 |2nd pair of lateral spines.
2nd pair of dorsal pits
and entapophyses.
Abdominal carapace.
ate sclerite stretch-
ing from the mouth|Chele.
to the chilaria). ed
The chilaria or paired| Digging legs.
metastoma, or meta-
thoracic sternites.
Soft integument and/Genital operculum.
stigmatic pits (mus-
cular), posterior to
base of operculum.
Epistigmatic pair of|lst gill-book pair
sclerites and stigma-| projecting.
tic pits.
Epistigmatic pair of/2nd gill-book pair
sclerites and stigma-| projecting.
tic pits.
Segments.
1 |Chelicers.
2 |\Chele.
6 |Walking legs.
Appendages.
3 |Walking legs.
4 |Walking legs.
5 |Walking legs.
LIMULUS AN ARACHNID.
SCORPIO.
537
Sternites.
Camerostome (of La-
treille), or upper lip.
Obliterated by the me-
siad extension of the
coxe of the four
walking legs; the
two anterior movable,
the two _ posterior
fixed. (In Mygalea
distinctly marked
small _ prothoracic
sternite is followed
by a large oval meso-
thoracic sternite.)
—_—_—._ _..____
Pentagonal elongate
sclerite or metatho-
racic sternite.
7 \Genital operculum. |Soft integument.
Tergites.
Cephalothoracie carapace
with central and peri-
pheral eyes.
A separate narrow band-
like sclerite.
8 |Pectine, or pair of|Separate small rect-|A separate narrow band-
comb-like organs ;| angular sclerite.
modified gill-book
projecting.
like sclerite.
9 \lst gill-book pair|Aseparate broadtrans-|A separate band-like scle-
sunkin pulmonary) verse sclerite with] rite.
sacs.
stigmata leading to
pulmonary sacs.
538
PROFESSOR E. RAY LANKESTER.
Segments.
Tergites.
|
10 [3rd pair of lateral spines.
3rd pair of dorsal pits
and entapophyses.
11 |4th pair of lateral spines.
4th pair of dorsal pits
and entapophyses.
12 |5th pair of lateral spines.
5th pair of dorsal pits
and entapophyses.
13 |6th pair of lateral spines.
6th pair of dorsal pits
and entapophyses.
14 |Only in the embryo this
segment is separate,
and has a 7th pair of
lateral spines.
segment is indicated.
These three segments
iy are never expressed
aud are represented
by the preanal re-
— gion of the telson.
18
Post-anal spine.
15 |Only in the embryo this
Abdominal carapace.
LIMULUS.
Sternites.
Epistigmatic pair of
sclerites and stigma-
tic pits.
Hpistigmatic pair of
sclerites and stigma-
tic pits.
Appendages.
3rd gill-book pair
projecting.
4th gill-book pair
projecting.
Kpistigmatic pair of|5th gill-book pair
sclerites and stigma-
tic pits.
projecting.
None.
Large and solid scle-
rite forming the ster-
num of the *‘Telson,”’
i.e. of the pree-anal
region of potential
segmentation, which
includes a soft inva-
ginate area on which
opens the ANUS.
None.
None.
None.
None.
None.
LIMULUS AN ARACHNID. 539
SCORPIO,
Segments.
Appendages. Sternites. Tergites.
10 |2nd gill-book pair/Aseparatebroadtrans-|A separate band-like scle-
sunk in pulmonary} verse sclerite with| rite.
sacs, stigmata leading to
pulmonary sacs.
11 |8rd gill-book pair|Aseparate broadtrans-|A separate band-like scle-
sunk in pulmonary| verse sclerite with) rite.
sacs. stigmata leading to
pulmonary sacs.
12 |4th gill-book pair/Aseparate broad trans-/A separate band-like scle-
sunk in pulmonary| verse sclerite with rite.
sacs, stigmata leading to
pulmonary sacs.
13 |None. A separate broad trans- A separate broad band-
) verse sclerite devoid) like sclerite.
| of stigmata.
4 IN one, : Ventral half of a dis-|Dorsal half of a distinct
tinct cylindrical scle-| cylindrical sclerite.
rite.
15 |None. Ventral half of a dis-|Dorsal half of a distinet
tinct cylindrical scle-| cylindrical sclerite.
rite.
16 |None. Ventral half of a dis-|Dorsal half of a distinct
tinct cylindrical sele-| cylindrical sclerite.
rite,
17 |None. Ventral half of a dis-|Dorsal half of a distinct
tinct cylindrical scle-| cylindrical sclerite.
rite.
18 |None. Ventral half of a dis-\Dorsal half of a distinct
tinct cylindrical scle-| cylindrical sclerite.
rite, in which is
placed the anus.
es te -
Post-anal spine or sting
(a jointed filame nt in T he-
lyphonus).
VOL. XXI.—NEW SER. N N
540 PROFESSOR E. RAY LANKESTER,
IV. The common characters of the lamelligerous appendages
of Scorpio and Limulus.—When we have once, on the ground
of a certain general agreement in structure and of a definite
identity in relation to other parts which correspond one to
another, started the hypothesis that the lamelligerous
appendages of the Scorpion agree each to each in their order
with the lamelligerous appendages of the King Crab, two
further proceedings are naturally the consequence. We
inquire first of all whether there are any less obvious agree-
ments in the structure of the organs compared which may be
brought out and made to give their testimony in favour of
our hypothesis, and, secondly, we inquire how can we form
a plausible conception of the origin of the two sets of struc-
tures from one set of organs present in a common ancestor
of Limulus and Scorpio? this last inquiry having especial
value, in that it may lead us to give due value to structures
present either in Scorpio or Limulus which had appeared
previously to have no special significance in the matter.
A close comparison! of the lamelligerous appendages of
Scorpio and Limulus—including under this head the
pectines and the pulmonary books of the former, anu the
branchial books of the latter—reveals the important fact that
they agree closely with one another in the mode in which
the lamelle are set upon the supporting axis
In all, we find an axis springing from the body wall,
transverse to which, on its posterior face, ave set 4 series of
lamelle. In order to compare one of these «ppendages
with another, it is necessary that all should be p.aved in one
and the same position. We must be careful not to compare
the anterior aspect of one with the posterior aspect of the
other. In the woodcuts, figs. 6 and 7, the posterior face of
the appendage as it hangs from its sternal attachment has
been represented.
There is no difficulty about determining this face for the
pectines of the Scorpion or for the branchial appendages of
Limulus, but the pulmonary books of the Scorpion require
some consideration. Supposing them to have once been
external, we must suppose that, with the gradual invagina-
1 The account which I give in the text of the lung-books of Scorpio
differs a good deal from that which is current, due to Joh. Muller as long
ago as 1828. I have not had specimens sufliciently well preserved to enable
me to determine the relation and possible adhesions of the proper wall of
the pulmonary sac (the invaginated sternal surface) to the lamellse, but have
freed the appendage from the investing membrane. I hope to be able by
the examination of fresh specimens to give on a future occasion a more
thorough account of the pulmonary sacs and lamelligerous appendages of
the Scorpion.
LIMULUS AN ARACHNID, Hil
tion of their surface of attachment, they have become more
and more deflected into the cavity of invagination, moving
on their fixed base at first backwards, then upwards, and
finally forwards. As we now find them (in a spirit speci-
men !), on viewing the inner surface of the ventral sclerites
by removing the terga and viscera, they can be rotated on
their hinge line so that they may be made to lie prone for-
wards, exposing the stigma or opening of the pulmonary
recess posteriorly, asin Pl. XXVIII, fig. 1 a, or they may be
made to lie prone in the reverse direction, hiding from view
the stigma, as shown in Pl. XXVIII, fig. 2 a, and in the
woodcuts, figs. 6 and 7. The position which corresponds
with that of the external appendages the pectines and the
branchial organs of Limulus, when viewed from the posterior
face, so as to show (in the case of Limulus) the lamelle, is
that in which the lung-book is directed backward so as to
hide the stigmatic aperture and is looked at from within the
Scorpion’s body, that is, by dissecting off the terga, viscera,
and muscles. ;
When the pectines, lung-books, and branchial books are
~ thas placed we find that the lamellz are not set precisely at
right anvles vpon the axes, but obliquely, so that there is
an imb ation of the successive lamelle. In all three it is
the p oxi! lameila which is uppermost (see Pl. XVIII, fig.
Zand x / and ig. 107’). The imbrication is identical in all.
As to nui)cr of lamelle, we find in the pecten of Buthus
Kochi eighteen (in other scorpions there are more or less) ;
in the lung-books of some scorpions! as many as 130, and in
the Limulus gill-book as many as 150. These numbers
vary slightly, increasing with growth in al! probability.
As to structure of lamelle, those of the pecten are more
solid and strongly chitinised than those of the other two
organs, but are, nevertheless, true ‘lamelle flattened
transversely.
Those of the lung-books are exceedingly delicate plates
composed of two closely approximated membranes, between
which the blood circulates ; they are, in fact, flattened bags.
They carry on their free margins a few chitinous spinules
(Pl. XXVIII, fig. 8). The lamelle of the gill-books of
Limulus are similarly delicate flattened bags with a setose
free border. I am not able to institute any comparison
of the histological structure of the lamelle of the Scorpion’s
lung-book with that of the King Crab’s gill-book, for
although I have been able to work out that of the latter on
: ' I believe the form in which I counted these to be a species of Androc-
onus,
542 PROFESSOR E, RAY LANKESTER,
fresh material, no such opportunity has yet presented itself
of investigating the Scorpion.
As to the shape of the lamellz, those of the pecten are
narrower and relatively thicker than those of the lung-books
or gill-books; the whole eighteen are also more nearly
equal to one another in size and shape. In the lung-books
the shape differs at the two extremities of the series a little,
and in size the proximal lamine are much larger than the
distal. The average shape may be described as that of a
broad scythe-blade (Pl. XXVIII, fig. 8) with a narrow base
support (@ 6). The lamellz of the gill-books of Limulus,
on the other hand, are approximately semicircular in shape,
with a wide base of origin (a8 in fig. 9, Pl. XXVIII).
Moreover an important difference, which is explained by
the convergence in place of divergence of the axis of the
limb relatively to the mid line of the body, is seen when the
lamellz of the gill-book and of the lung-book are compared,
in the fact that in the gill-book the proximal lamine are
the smallest (Pl. XXVIII, fig. 107’), whilst in the lunc-
book they are the largest.
Further comparison of the grouping and form of the —
lamellz is facilitated by the figures on Pl. XXVIT1, where
fig. 1 and fig. 1a, fig. 2 and figs. 2a@ and 10, fig. 3 and
figs. 3a and 34, give representations of the three varieties of
lamelligerous appendages in a series of identical positions.
Fig. 1 should, for comparison with fig, 1 a, be \ocked at by
inverting the plate.
The axes which support the lamelle in the three varieties
of lamelligerous limb differ much from one another, but in a
manner directly corresponding with obvious functions.
The pecten has a large free axis firmly chitinised, imper-
fectly divided into two joints. It is flattened by antero-
posterior pressure. The function of the pecten is not
actually known, but it appears to be tactile. It is not
respiratory, and the Scorpion is of terrestrial habit; hence
its comparatively solid character and protective development
of chitin.
The gill-book of Limulus is supported on an axis, which
is flattened by dorso-ventral pressure, protection being thus
afforded to the otherwise naked and very delicate lamelle.
It is not free except at its extreniity, where it exhibits a
fointing of separate chitinous plates. Its base is very wide,
and is attached, not to a flat sternal surface, but to an out-
standing sternal lobe, which extends between the bases of
fellow-appendages, and gives rise to a teat-like soft process
in the median line (Pl. XXVIII, m d, fig. 10). The charac-
LIMULUS AN ARACHNID. 543
ter of this axis is obviously an adaptation to the branchial
function of the lamella combined with a locomotor
function.
The lung-book of Scorpio has no locomotor function, and
it is protected by the recess of the sternum, in which it lies,
It is not tactile, nor is it exposed to desiccation and rough
usage, as are the pectines. It is specialised for respiratory
purposes. The axis is exceedingly small and simple, for
the greater part of its length adherent to the invaginated
sternal wall, leaving, however, a small free distal portion
(see Pl. XXVIII, fig. 2a). Its walls are quite free frem
chitinisation, and of great delicacy. It is little else than a
horizontal vascular tube supporting the lamelliform bags
into which its cavity leads (Pl. XXVIII, 24a, d).
Though the axis is here reduced to its simplest ex-
pression, it is not possible to overlook init the representative
' the vertically compressed chitinised axis of the pecten,
anc © the horizontally compressed chitinised axis of the
’. Hypothesis as to the mode of origin of the three varieties
ol lameiligerous appendages in Scorpio and Limulus.—The
view which I have advanced in this memoir as to the prac-
(ical identity of the gill-books of Limulus and the lung-
oooks of Scorpio implicitly contains the affirmation that either
the structures of Limulus have been derived from those of
Scorpio, or those of Scorpio from those of Limulus, or that
a third (now extinct) form has given rise to both Limulus
and Scorpio. Further, it is to be observed that such
extinct form might be more like to Limulus than to
Scorpio, or vice versdé, in respect of any particular element of
structure.
To make a long story as short as possible I may say that,
without prejudicing the recognition of the (as I think) well-
established morphological identities above pointed out, we
may best explain their existence by assuming that an aquatic
form breathing the dissolved oxygen of the water inhabited
by it, by means of book-like gills, was the common ancestor
of Limulus and of Scorpio. From the book-like gills of this
ancestral form the broad series of Limulus and the narrower
lung-books, as well as the pectines or combs of the Scorpion,
have been derived. The form of the book-like gills of this
Arachnidan ancestor was probably something intermediate
between the three existent modifications of it, and best con-
ceived of, perhaps, by imagining the teeth of the Scorpion’s
“‘ pectinate organs” to become soft and flattened and
increased in number (see Pl, XXIX, fig. 1).
544A PROFESSOR E. RAY LANKESTER,
To obtain from these the Limulus gill we have but to
suppose certain definite changes of dimension, the imbrication
and character of the lamelle, and their external position
remaining unaltered (Pl. XXIX, figs. 2 a and 3 a).
To arrive at the book-lungs of the Scorpion, we have to
imagine the ventral surface on each side in close proximity
to the short appendages carrying the gill-books—to have
become deeply cupped or depressed, so that two series of
cup-like pits should be formed, a right and a left, a pair
being placed in each segment, correspending to each pair of
gill-books. Each cup must have become so large in area
and so deep as to embrace within its limits the relatively
small adjacent gill-book (XXIX, fig. 26). Further, when
once the gill-book had been involved in this cup-like de-
pression, the walls of the cup must have tended to grow
together so as to forma pulmonary chamber with only a
narrow slit-like opening to the exterior (Pl. XXIX, fig. 3 4),
and pari passu with this closing in of the cupped area, and
the protection of the respiratory lamellz, the Arachnid must
have acquired the power of leaving the water and of brew ing
the atmospheric oxygen admitted to the damp «amber
formed by the cave-like areas of depression. ae,
Whilst framing such a hypothetical accoun! of the way in
which the transition from naked “gill-bo.k’ to Intsunken
« Jung-book” could have taken place, one naturally
asks—“Is it not somewhat gratuitous ‘9 ® sume that
cupped arez should form conveniently i side of
the gill-books of the aquatic ancestor, so as ©) Le ready to
increase in size, and ultimately draw into themselves, as it
were, the gill-books?” ‘Is there,” we are led on further to
ask, “ any known instance in Arachnida of the formation of
cupped aree on the chitinous surface of the body? If so,
can we show in what mechanical relation they are formed ?
And, lastly, can it -be demonstrated that such mechanical
relation probably existed in connection with the gill-books
of the assumed common ancestor of Limulus and Scorpio ?
If all these questions can be affirmatively answered, then
our hypothesis as to the transition of the aquatic Arachnid
to the pulmonate condition acquires great plausibility.
The answer to these questions appears to me to have more
than ordinary interest, since the formation of cupped arez
on the chitinous surface of the body and the mechanical
relations connected with their formation have, as pointed out
a few pages back, come to light as demanded by the hypo-
thesis. They exist in Limulus itself and in Thelyphonus.
In Limulus there are two great muscles, a right and a left,
LIMULUS AN ARACHNID. 545
inserted into the soft ventral integument near the base of
each double gill-plate. These muscles serve (together with
others that enter the appendage itself) by their contractions
to move the gill-plates in the water and so aid in aquatic
respiration. The position of the insertion of each muscular
mass is marked by a deep funnel-like depression of the
integument. From the external surface this depression
appears as a “stigma,” which we have already described as
the parabranchial stigma. The funnel-like depression has a
narrow mouth which is often as much as half an inch in
length. Internally the invaginated cuticle stands up as a
flexible tendon clothed with fibrous tissue and giving attach-
ment to the muscle already mentioned.
In Limulus we find a pair of these “ muscle-stigmata,”
right and left behind the genital operculum, and a pair
(right and left) behind each of the lamelliform fused appen-
dages which carry the gill-books.
We have only to suppose the appendages carrying the
gill-books not to have fused as yet in the middle line, and
the muscular stigmata to have become greatly developed
(perhaps by increased development of the muscle aiding in
aquatic respiration when the appendage itself grew small
and therefore less efficient) and we have at once the gill-book
sinking within the area of the stigmatic pit, Pl. XXIX,
fig. 25.
A very important feature in the supposed further develop-
ment is the correspondence of the atrophy of the muscle
(which atrophy is required to fit in with our hypothesis, and
to convert the muscle-pit into a pulmonary sac) with the
changes in the structures which would necessarily result
were the physiological conditions gradually to become such
as to favour aérial in place of aquatic respiration. The
violent agitation of the gills by the muscle attached to the
stigmatic pit would become useless, supposing an exposure
of the gill-lamelle to the atmosphere became by degrees
habitual with the ancestral Arachnidan. In proportion as
these hypothetical creatures acquired the habit of aérial
repiration—the deepening and arching in of the stigmatic
pit would be favoured, and the atrophy and final disappear-
ance of the muscle which was attached to its inner surface,
and mechanically brought it into existence, would also be
directly promoted.
A further confirmation of the view now advanced is found
in the remarkable East Indian Arachnid Thelyphonus. This
Arachnid has not four pairs of lung-sacs like Scorpio, but
only two pairs, corresponding to the two foremost lungs of
546 PROFESSOR E, RAY LANKESTER,
Scorpio, and to the second and third gill-book-pairs of
Limulus (woodcut, figs. 12, 13, 14). Nevertheless, as we
have seen in a previous section of this Essay, the four seg-
ments of the abdomen posterior to these are each marked by
a par of shallow stigmata placed in line with the orifices of
the pulmonarg sacs of the two anterior segments, msg. When
the internal structure corresponding to these parts is exa-
mined, it is found that a large muscle (similar to the simi-
larly placed muscle of Limulus) is inserted into each of the
four right and four left stigmata in the segments posterior
to the pulmonary sacs (woodcut fig. 14, m.) The two seg-
ments into which the two pairs of pulmonary sacs are sunk,
have xo such muscles. The pulmonary sacs are, therefore,
to all appearance, enlarged muscular stigmata, from which
their former muscles have disappeared by disuse and
atrophy.
VI. The Entosternite—Leaving now the comparison of
segments and appendages, which is undoubtedly the most
important element in determining our judgment as to the
affinity of Limulus with Scorpio, we come to the considera-
tion of a number of other structures, which we shall find
some more and some less favorable to the hypothesis of a
close relationship between the two animals.
Connected with the exoskeleton and locomotor system is
that remarkable development of an endoskeleton in the
Arachnida, which Straus Durkheim put forward in the
passage cited at the commencement of this article, as one
of the leading characteristics of the class and one of the
obvious features in which Limulus shows itself to be a true
Arachnid.
As already remarked, in speaking of the entapophyses and
parabranchial stigmata, Limulus shows a marked tendency
to the development of cartilage and fibro-cartilage by the
modification of its connective substance at certain points and
in certain areas.
The most striking result of this tendency, is the formation
of a large fibro-cartilaginous plate which lies in the cephalo-
thoracic region between the alimentary canal above and the
nerve collar below, and unconnected by hard parts with any
portion of the exoskeleton. It is represented of the natural
size as seen from the ventral (sternal) aspect in fig. 7,
Pl. XXVIII. It has been previously figured by Van der
Hoeven (12), whose figure is not very accurate, and is copied
by Owen (7). be
This body is the base of origin of a large number of
muscles, and may be regarded as an enlargement and
LIMULUS AN ARACHNID 547
interlacing of their respective tendons. In the figure,
nothing but the skeletal structure, cleaned of its muscles, is
represented.
In Scorpio, a similarly shaped loose skeletal piece is
ound, which gives attachment to muscles in the same way
and has a similar relation to the. ventral nerve-mass and
artery, by which in Scorpio it is perforated (Pl. XXVIII,
figs. 6 and 6 a). The corresponding body in Mygale is
(Pl. XXVIII, figs. 5,5 a) more closely similar in form to
that of Limulus than is that of Scorpio.
In order to make a close comparison of these Entoster-
nites, it will be necessary to determine exactly the insertions
of the muscles to which they give origin; and further, to
ascertain how far the histological structure of those of Scor-
pio and Mygale agrees with that of Limulus. The results
of this investigation I hope to make the subject of a future
publication. In the meantime the close correspondence in
general character of the three Entosternites figured on
Pl. XXVIII cannot escape notice, and fully justifies the
importance which Straus Durkheim attached to them. The
two pairs of tendinous outgrowths right and left of the
central plate in Limulus correspond with the three pairs
seen in Mygale, whilst the deep anterior notch in the latter
corresponds with the shallower excavation in Limulus, in
which the number 7 is placed in the drawing, and in which
in the animal itself the bend of the alimentary canal is
placed, the mouth being actually below the central region
of the plate, so that the alimentary canal passes first for-
wards beneath the plate and is then reflected so as to pass
backwards whilst resting on the upper surface of the plate.
‘Whilst of this as of so many other structures of the
Arachnida (such as the lung-books, &c.) which have been
compared in the present memoir with structures in Limulus,
a renewed and critical examination is absolutely needed,
yet we have sufficient ground, even in our present
incomplete knowledge, for concluding that the agreement
as to them presented by the two animals is a very close
one.
In no Crustacean is a free entosternite at all similar to
the organ under discussion known. The apodemes of the
sternal surface of Decapodous Crustacea do not resemble it
in form though of a similar function. The nearest approach
to it is seen in the rod-like skeletal organ found in the
abdomen of Lepidoptera, and described by Leydig (‘ Bau
des Thierischen KGrpers,’ Atlas, pl. vi, fig. 1). Its
shape and position are very different, however, from the
548 PROFESSOR E. RAY LANKESTER.
entosternites of Limulus and other Arachnida. It agrees
with these only so far as that it is a free internal skeletal
iece.
4 In the abdominal region of Limulus small loose fibro-
cartilages, similar in nature to the Entosternite, are found,
connected with the tendons of muscles. I have isolated
four such pieces. They are mentioned by Straus Durkheim.
(To be continued.)
MEMOIRS.
The Oxcan of Jacopson in the Rassir. By H. Kuziy, M.D.,
F.R.S., Lecturer on Histology and Embryology in the Medical
School of St. Bartholomew’s Hospital. (With Plates XXX
and XXXII.)
In continuation of the research of the organ of Jacobson in
mammals, that of the guinea-pig having been described in the
January and April numbers, 1881, of this Journal, I now propose
to give the results of the minute examination of this organ in the
rabbit. The differences in the microscopic anatomy of Jacob-
son’s organ in these two rodents are very great indeed, much
greater than could be anticipated. That of the rabbit in many
respects comes very close to the ideal type which Gratiolet1
draws and describes, and is also similar to the organ in the sheep
as described by Balogh. The points of resemblance between
that of the rabbit and the sheep and the points of dissemblance
between that of the rabbit and the guinea-pig will be fully dis-
cussed below.
In describing the organ of the rabbit, we shall take note, as
we did in the guinea-pig, of the surrounding parts, in the region of
the organ of Jacobson, since all the parts constituting the organ
of Jacobson bear an intimate relation to the tissues around them.
In the rabbit, the facial part of the head being longer than in
the guinea-pig, it naturally follows that the nasal septum, and
consequently also the organ of Jacobson, are of greater length in
the former than in the latter animal. When fully exposing the
front part of the septum nasale, from the dorsum of the nose to the
lower nasal furrow, by removing the lateral wall of the nose as
well as the lower concha or lower turbinated bone—which by its
very beautiful plication contrasts in a conspicuous manner with
the comparatively smooth lower concha of the guinea-pig—the
1 ‘Recherches sur l’organe de Jacobson,’ Paris, 1845, p. 19, aud passim,
2 *Das Jacobson’sche Organ des Schafes, Sitzungsb. d. K. Akad. d,
Wiss.,’ xlii, p. 449.
VOL. XXI.—NEW SER. 00
~—
550 DR. E. KLEIN,
organ of Jacobson is easily perceived as a bilateral tubular bulg-
ing, extending in the septum along the lower nasal furrow.
The outer wall of each organ or tube, 7.e. the one actually
seen—the other, or median wall, being hidden in the septum—
is marked by its rich supply of large blood-vessels, constituting,
as will be mentioned below, the cavernous layer of the tubes.
The length of the tubes in a medium-sized rabbit is from 1°5
to 2 centimétres, and already with the unaided eye it can be
ascertained that each tube rather sharply tapers towards its ante-
rior and posterior extremity.
Making transverse sections through the front part of the nasal
organ, the following cartilages are met with :—
1. The cartilage of the septum. ‘This is hyaline cartilage,
staining deeply in logwood, except the part next to the dorsum
of the nose, this part being triangular in section, and not
staining well in logwood. Between the two divisions there is
this great difference: that in the former the cartilage cells are
very much closer in position than in the latter, they being here
arranged more distinctly in groups of two, four, six, or eight cells,
separated by relatively large masses of hyaline ground substance.
In logwood-stained specimens the hyaline matrix, as well as the
cells, are very slightly stained in the upper part, whereas they
assume a deep colour in the lower part of the septum. In both
divisions, but especially in the upper one, the cartilage cells con-
tain in their substance several small oil globules or one large oil
drop. Next to the perichondrium, the cartilage cells are small,
flattened parallel to the surface, whereas in the centre of the
cartilage the cells, or rather their groups, are arranged more or
less transversely ; a similar distinction, as is well known, F. HE.
Schultze,! has noticed in the bronchial cartilages.
The close position of the cells in the lower part and the deep
staining of this latter, appear to indicate that a more active growth
is taking place in it than in the upper portion of the septal
cartilage.
This cartilage increases in height and thickness, especially its
lower margin becomes conspicuous by its enlargement, as we
pass backwards in the region of the organ of Jacobson.
2. The cartilage of the lateral wall. A transverse section made
in the region of the incisors, shows us on each side in the lateral
wall of the nasal cavity, rising from the lower nasal furrow, and
forming the support of that wall, a cartilage plate, extending with
a somewhat broad projection into the front or smooth part of
the lower concha. In connection with it is a thin cartilage
plate, extending laterally and upwards in a curved manner. In
fig. 1 these cartilages are well shown. ‘The first, i.e. the one
1 ‘Stricker’s Manual of Histology,’ article ‘‘ Bronchi and Lung.”
THE ORGAN OF JACOBSON IN THE RABBIT, 551
forming the support of the lateral wall of the nasal furrow, will
be spoken of as the lower limb ; the second, z.e. the one forming
the support of the front part of the lower concha, as the upper
limb; and the third, z.e. the one extending outwards and upwards,
as the lateral limb. In a section anterior to fig. 1, the lower limb,
shown in fig. 1, is not present yet, but outside it is a small car-
tilage plate coming off from the lateral limb and extending a short
way downwards. Where the other limbs join the lower limb, this
latter has its thickest diameter. The upper and lateral limbs
increase also in thickness towards their upper margin.
As regards the structure of these different parts, the same dis-
tinction can be drawn as in the septal cartilage, viz. the upper
portions of both the upper and lateral limbs stam much less in
logwood, and the cartilage cells are relatively fewer than in the
lower parts.
In a preparation in front of the one of which fig. 1, is a repre-
sentation, the three limbs of the above cartilage form one conti-
nuous whole; but in the preparation shown in fig. 1 there is
already a discontinuity noticed, at any rate on one side, between
the upper and lower limb, as well as between the latter and the
lateral limb. Going a little further back, e.g. fig. 1, we notice
not only a permanent discontinuity between the two last-named
limbs, but we perceive that the upper limb of the cartilage
becomes greatly reduced in height, being now represented only
by its upper less stained portion, soon to disappear altogether, and
to be replaced by the rudiments of spongy bone, forming now the
support of the plicated lower concha. While this happens with
the upper limb, also the lower limb undergoes considerable
changes, viz. it increases in height and thickness, and its lower
_ Inargin, while greatly expanding in breadth, curves downwards
and inwards, in the manner of a trough or hook, but so that the
nasal furrow is now forming the lining of its (i.e. the trough’s)
concavity. In fig. 2 this so changed lower limb is accurately
delineated.
It is here seen that the trough consists of an inner or median
labium, terminating close to the lower margin of the septal car-
tilage with a pointed extremity and an outer or lateral labium
continuous with the lower limb of the cartilage above mentioned.
From the convex surface of the trough a short cartilage extends
downwards into the upper maxillary bone. This cartilage is not
well seen in fig. 2, but is observed well in sections taken between
the parts of figs. 1 and 2. Ina part of which fig. 2 is a repre-
sentation it is just disappearing.
As will be shown soon below, this trough-shaped cartilage is
the front end of the cartilage that forms the support of the organ
or tube of Jacobson, and it is known as Jacobson’s cartilage.
552 DR. E. KLEIN.
Going alittle further back than fig. 2, we find that Jacobson’s
cartilage changes in two ways: first, the curve itself is not any
more the lowest point, but has become turned slightly inwards,
2. é. in a median direction, and, secondly, there is an indication
of its severance from the rest of the lower limb of the cartilage
of the lateral wall of the nasal furrow.
In fig. 3 both these changes are well shown. Still further back
the severance is complete, and Jacobson’s cartilage forms now an
independent and well-defined organ, of the shape and position
shown very accurately in fig.3. Itis here noticed that the inner
or median labium is considerably different in shape from that in
fig. 2; it still terminates with an upper sharp margin next the
septal cartilage, but is possessed of a short triangular
projection.
As is shown in fig. 3, the lower nasal furrow becomes invagi-
nated into the concavity of Jacobson’s cartilage as the mouth of
the organ of Jacobson, in exactly the same way as was pointed out
in my last paper (‘ Quarterly Journal of Micr. Science, April,
1881) of Jacobson’s organ of the guinea-pig. We must for
the present omit to enter into a detailed description of this open-
ing, since we shall return to it further below; at present we will
only concern ourselves with Jacobson’s cartilage, and trace this
backwards all along the organ of Jacohson, of which it forms
the chief support.
The next shape of Jacobson’s cartilage after the one shown
in fig. 3 is one illustrated in fig. 4, that is, the extremities of
the two labia have joined, and Jacobson’s cartilage forms now
a complete capsule around the organ of Jacobson, which is
a complete tube (13, fig. 4). In this shape it resembles
Jacobson’s cartilage in the guinea-pig in about the anterior half .
of the organ of Jacobson, as illustrated in fig. 1 of my first paper
on this subject (‘ Quarterly Journal of Micr, Science,’ January,
1881). In some sections through this region I notice that the
median walls of the capsule of Jacobson’s cartilage of the two
sides are more or less continuous with one another to a very small
extent in the lower part. But in this shape Jacobson’s cartilage
does not extend for any considerable distance, any more than was
the case in the guinea-pig, for in the rabbit it soon changes in
this manner, that the capsule is discontinuous in the upper wall,
but slightly directed outwards, so that we again distinguish an
outer or lateral from an inner or median labium. Owing to this
discontinuity being established, not in a straight upward, but
slightly oblique and outward direction, it follows that the median
Jabium is longer than the lateral one.
The next change is this: the extremity of the outer labium
?
THE ORGAN OF JACOBSON IN THE RABBIT. 558
becomes much thickened, while the median labium is prolonged
in an upward direction. The thickening of the extremity of the
lateral labium is soon again lost, but the median labium, to the
hind end of the organ of Jacobson, goes on steadily increasing
in height, the lateral labium in its height remaiming tolerably
stationary. The greater part of the organ of Jacobson is sur-
rounded by the cartilage of this nature, 7. e. a trough- or hook-
shaped plate, of which the median labium is much higher than
the lateral one, the former resting with its upper extremity alone
against the thickened lower margin of the septal cartilage. The
cartilage becomes, at the same time, thinner as it is traced back-
wards. Figures 5 and 6 show these points very clearly. All
the figures having been drawn with the camera lucida the rela-
tions of size, shape, and position are perfectly exact.
From the relative length of the median labium of Jacobson’s
cartilage alone it is easily possible to decide which of two sec-
tions is more anterior, viz. the one whose median labium is
shorter.
As the hind extremity of the organ of Jacobson is approached
this important change takes place, viz. the lateral labium turns
inwards with its upper extremity, as if to close against the
median labium, and the part of this latter that extends above
this line sooner or later becomes discontinuous from the rest
(see figs. 8 and 9), and, gradually becoming shorter, altogether
disappears, so that at the very extremity of Jacobson’s organ,
viz. when the organ of Jacobson has dwindled down to an ex-
ceedingly fine tube, the cartilage of Jacobson appears in a
transverse section of an annular shape, open inwards and out-
wards.
The cartilage of Jacobson extends a very short distance beyond
the tube of Jacobson, and it is then only with the median wall,
which, however, soon altogether disappears.
Comparing, then, Jacobson’s cartilage in the rabbit with that
of the guinea-pig, as described in my former papers, we see this
remarkable difference, that in the rabbit the cartilage extends as
far as the organ of Jacobson, and even beyond it, while in the
guinea-pig a considerable posterior portion of the organ of
Jacobson is without any cartilage, but is surrounded entirely
by the bone of the crista nasalis of the superior maxilla (see
Plate XVII, fig. 7, of this Journal, April, 1881).
The anterior extremity of Jacobson’s cartilage is in both ani-
mals very different, as is noticed on a comparison of figs. 3, 4, 5,
6, of my paper in this year’s April number of this Journal with
the figures of the present memoir.
In the guinea-pig Jacobson’s cartilage having formed a com-
plete capsule, going backwards hecomes again incomplete, the
5d-4 DR, E. KLEIN.
deficiency affecting the lower and outer wall, the plough-shaped
upper wall (see fig. 2, Pl. VII, in this year’s January number of
this Journal) being the last part of Jacobson’s cartilage to dis-
appear. In the rabbit, on the other hand, it is the outer and
upper part of the capsule which becomes wanting, so that Jacob-
son’s cartilage represents a hook-shaped or trough-shaped organ,
the opening being in the upper part of the wall.
As regards the presence of an inner and outer Jabium, and as
regards the elongation of the former as we pass backwards, there
is nothing of the kind in the guinea-pig. The cartilage of Jacob-
son agrees in its general shape, 7.e. being a trough-shaped plate
with its opening directed upwards, more with the ideal cartilage of
Jacobson described by Gratiolet! of the mammal, and to some
limited extent also with that of the sheep, mentioned by Balogh,’
and figured by him in figs. 15, 16, and 17 of his plate iv, being
here represented in some places as a trough-shaped capsule with
an upper opening.
Another point of dissemblance between the cartilage of Jacobson
in the rabbit and guinea-pig is its relation to the upper maxil-
lary bone.
As I have shown in figs. 4, 5, and 6 of Plates XVI and XVII
in the April number, 1881, of this Journal, the cartilage of
Jacobson in the guinea-pig 1s supported already in the most
anterior part of the organ of Jacobson, and even at the mouth
of this latter, by a lamina of osseous substance extending on each
side from the superior maxilla on the inner or median surface of
Jacobson’s cartilage. This bone is in reality the front part of
the crista nasalis of the superior maxilla. When Jacobson’s
cartilage has assumed the shape of a more or less perfect
capsule, the bone forms an almost complete capsule around
Jacobson’s cartilage, as is shown in figs. 1 and 2 of Plate VII
in this year’s January number of this Journal. In the pos-
terior portion of the organ of Jacobson the cartilage of Jacobson,
as mentioned previously, disappears altogether, and now the
organ of Jacobson is altogether surrounded by the bone of
the crista nasalis of the superior maxilla. Thus it is in the
guinea-pig; in the rabbit the relations are altogether of a differ-
ent nature, as is shown in figs 4 to 8.
In the rabbit Sacobson’s cartilage is supported on its lower
wall by the intermaxillary bones separated in the median line by
their respective inner periosteum. ‘This relation is noticed already
before any trace of the organ of Jacobson is reached, and it remains
the same past the region in which Jacobson’s cartilage has assumed
the shape of a complete capsule (see fig. 4). Soon after this
Vine, p. ZL.
7 L.c., p. 451.
THE ORGAN OF JACOBSON IN THE RABBIT, 355
place, when Jacobson’s cartilage becomes changed into a trough-
shaped capsule with an upper opening, there is seen along its
outer or lateral labium, and gradually elongating so as to reach up
to tle upper extremity of this latter, a lamina of bone extending
from the lateral portion of the intermaxillary bone; this condi-
tion is accurately illustrated in figures 5—9. It is also noticed
that this osseous lamina supporting the outer labium of Jacob-
son’s cartilage increases slightly in thickness towards its upper
extremity. In the posterior extremity of the organ of Jacobson
also the inner or median labium of Jacobson’s cartilage receives
a bony support from the median portion of each intermaxillary
bone, in the shape of an osseous lamina extending for a relatively
short distance in the median line separating the Jacobson’s car-
tilage of the two sides (see fig. 8). But in no place does the
organ of Jacobson, or rather Jacobson’s cartilage, receive a sup-
port from the intermaxillary bones to such an extent as is the
case In the guinea-pig. ha
In addition to the cartilages described hitherto there exists a
cartilage in the rabbit which, as far as I can see, is not represented
in the guinea-pig, viz. a curved or trough-shaped plate of hyaline
cartilage, the concavity of which coincides with the lower nasal
furrow; the mucous membrane of this latter forms indeed the lining
of that trough-shaped cartilage plate. The most anterior point
where this cartilage is met with is the one depicted in fig. 4; it will
be seen that Jacobson’s cartilage is a closed capsule and that the
mucous membrane of the lower nasal furrow is supported by a
trough-shaped cartilage plate ; on one side the lower nasal furrow
appears closed as if.to form atube. ‘The fact is, that we have
here on one side of the section the upper extremity of the Stenson’s
or Stenonian duct, or the naso-palatine canal, while on the other
side the communication of this duct with the lower nasal furrow
is seen widely open.
Just as in the guinea-pig so also in the rabbit, the Stenonian canals
open into the nasal furrow, and are not in any way in a direct communica-
tion with the organ of Jacobson.
The trough-shaped cartilage plate just named as supporting
the mucous membrane of the lower nasal furrow is in reality a
continuation of Stenson’s cartilage, z.e. the cartilage forming the
support of Stenson’s duct, and for this reason the former may be
called the Stenson’s or Stenonian cartilage. It extends as far as the
organ of Jacobson does (see fig. 9) and terminates with Jacobson’s
cartilage. It is uninterrupted in its whole extension and does not
alter in shape, size, or thickness, except at its posterior extremity,
where it suddenly becomes shorter and thinner.
556 DR, U. KLEIN.
T now come to the essential part of this paper, viz. the descrip-
tion of the structure of the tissues forming the wall of the organs
or tubes of Jacobson.
In the guinea-pig, as has been pointed out in my paper of
this year’s April number of this Journal, the mucous membrane
lining the depth of the nasal furrow is in the front part of the
nasal organ covered with stratified pavement epithelium, and the
mucosa itself contains, like the mucosa of the neighbouring parts,
a plexus of veins longitudinally arranged and is infiltrated with
numerous lymph-corpuscles. The same epithelium and structure
of the mucous membrane of the nasal furrow, except that the
infiltration with lymph-corpuscles is here much less marked than
in the guinea-pig, is also met with in the front part of the nasal
organ of the rabbit, and I can therefore pass this over without
any further details, and will refer the reader to figs. 1, 2 and
3, of the present memoir.
As in the guinea-pig, so also in the rabbit, there exists an
open communication of the tubes or organs of Jacobson with
the lower nasal furrow by means of a narrow mouth, such as is
shown in fig. 3.1. In front of this opening we notice in the
mucous membrane of the nasal furrow a conspicuous plexus
of large veins, the tissue between which contains bundles
of muscular tissue, that is to say, we have here already to deal
with a cavernous tissue similar to that occurring in the lateral
wall of the organ of Jacobson, at and about. the mouth, such as is
represented in fig. 8. The cavernous tissue is a conspicuous part
of the mucous membrane and occupies the part of this latter which
corresponds to the lower wall of Jacobson’s cartilage. The part
of the mucous membrane corresponding to the median labium of
Jacobson’s cartilage is more or less occupied by glands extending
downwards and upwards, so as to form a continuity with those
contained in the mucous membrane of the nasal furrow and septum
respectively.
All these glands, be it said once for all, whether in the wall of
Jacobson’s organ, or in the mucous membrane of the nasal septum,
or the concha inferior, or the wallsof the nasal furrow, are always
serous glands of exactly the same nature as those described in my
former papers; the ducts are lined with a single layer of columnar
cells, whose outer portion is conspicuously fibrillated, just as in the
salivary tubes of Pfliiger.
The mouth of Jacobson’s organ is lined with stratified pave-
ment epithelium; the subepithelial tissue contains numerous
lymph-corpuscles. Immediately past the mouth the epithelium
is stratified columnar all round the lumen of the now closed tube
1 My friend Dr. Reuben Harvey, of Dublin, informs me that he found
the same condition also in the rat and cat,
THE ORGAN OF JACOBSON IN THE RABBIT, 557
or organ of Jacobson. ‘The lumen here is circular in transverse
section. The superficial layer of the epithelium is made up of
conical or cylindrical, the deepest of inverted conical cells, and be-
tween the two are pushed in more or less numerous spindle-shaped
cells. The glands occupy ali parts of the cavity of Jacobson’s
cartilage except the part corresponding to its lower walls, which
is occupied by the cavernous tissue. Compare fig. 3.
Immediately after this point, z.e. the closed tube with circular
lumen—but the Jacobson’s cartilage is not yet a closed capsule—
the shape of the organ and the disposition of its parts change in
this manner: the lumen is now oval in transverse section,
the long diameter being placed in an upward and downward
direction. The walls of the organ of Jacobson may consequently
now be considered as the median and Jateral wall, and the sulci
where the two meet will be considered, as was the case in the
guinea-pig’s organ (see my former paper), as the wpper and lower
suleus. The epithelium lining the lumen is stratified columnar as
described above, except on the median wall, where it is sensory
epithelium, the structure of which will be considered minutely
below. The sensory epithelium is not directly continuous with
the epithelium lining the upper and lower sulcus of the organ.
Tn connection with the epithelium of the median wall is a lymph
follicle of considerable size. This follicle occurring in several
successive transverse sections it follows that we have in reality
to do with a patch of lymph-follicles extending in a longitudinal
direction.
The lymph-follicle, together with the numerous bundles of the
olfactory nerve branches (see below), occupy a great part of
the median wall; the upper part of this wall, and the whole
region above the upper sulcus, is filled with serows glands
whose ducts open into the upper sulcus. The lower part of the
median wall is occupied by a plexus of large veins which, different
from the cavernous tissue, do not contain any non-striped
muscle in the interstitial tissue. The part of the wall imme-
diately below the lower sulcus is occupied by serous glands
which send their ducts into the lower sulcus ; they are far less in
number than those of the upper sulcus.
The remainder of the wall of the organ of Jacobson, i. e. the
lateral wall, 2s occupied by the cavernous tissue—a plexus of
venous vessels or sinuses separated by, and embedded in, a mesh-
work of bundles of what appears to be non-striped muscular
tissue. The venous vessels extend in a longitudinal direction,
while the bundles of muscle cells extend prevalently in a radiating
direction from the cartilage towards the lumen of the organ.
At this point which we are now describing the epithelium of
the lateral wall vests on a thin layer of mucous membrane densely
558 DR. E. KLEIN.
infiltrated with lymph-corpucles; this subepithelial layer is
limited by a thin layer of elastic fibres running chiefly in a
longitudinal direction, and it is this elastic layer, which, while
forming the inner boundary of the cavernous tissue represents
at the same time the inner insertion of the bundles of non-striped
muscular cells mentioned above.
The next point we have to consider is the constitution of the
walls of Jacobson’s organ at a point a little further behind the
one just described, 7. e. when the cartilage of Jacobson has
become closed so as to form a complete capsule, such as is
represented in fig. 4. The distribution of the different tissues
as just described is very much the same, except that the epithe-
lium of the lateral wall is separated from the elastic layer by a
measurable stratum densely infiltrated with lymph-corpuscles.
The elastic layer is very conspicuous.
The cavernous layer, the distribution of the glands at the
upper and lower sulcus, the sensory epithelium and the occur-
rence of lymph-follicles, the presence of olfactory nerve trunks
and plexuses of fine bundles of these in the median wall, is the
same as in the parts anterior to this place.
We have mentioned on a former page that past the region
of the closed Jacobson’s cartilage capsule we again find this
cartilage open in the upper part, assuming the shape of a
trough, so that its cavity is in a free communication with the
tissue at the side of the septal cartilage (see fig, 5), and we have
also stated above that, beginning with this region, and through
the greatest part of the crgan of Jacobson, the relations remain
of this nature, with this difference, that as we pass farther back-
wards the median or inner labium of the trough gradually increases
in length.
Now, with the change of the Jacobson’s cartilage from ak
closed capsule into a trough-shaped plate, there occurs a very
interesting change in the wall of the organ of Jacobson; the
median wall, it is true, remains the same, and so does the dis-
position of the glands of the upper and lower sulcus as well as that
of the cavernous tissue and of the elastic layer in the lateral wall,
but the subepithelial layer of the lateral wall alters so that this
whole wall assumes a different aspect. Previously, we saw the
epithelium of the lateral walls separated from the elastic layer by
a thin layer of connective tissue densely infiltrated with lymph-
corpuscles ; now, however, this subepithelial layer becomes greatly
thickened, owing to the presence of serous glands, which oceupy
the middle of the layer, so that this middle part of the lateral
wall becomes changed into a fold forming a conspicuous projec-
tion into the cavity of the organ of Jacobson. This fold may be
therefore called the glandfold of the lateral wall. These glands
THE ORGAN OF JACOBSON IN THE RABBIT, 559
send their ducts through the epithelium of the lateral wall verti-
cally and straight through the middle of the lateral wall. These
glands do not extend through the whole subepthelial layer from
the upper to the lower sulcus, but are limited chiefly, as stated
above, to the middle part of the lateral wall, hence the fold;
above and below the gland the subepithelial layer contains
numerous lymph-corpuscles as before.
This glandfold remains now through the whole length of the
organ of Jacobson to near its posterior extremity.
The presence of this glandfold in the lateral wall necessitates
a change in the shape of the cavity of the organ of Jacobson;
whereas the cavity in transverse section through the anterior
regions appears more or less oval, it now for obvious reasons
possesses the shape of a bean or kidney (compare figs. 10 and 11).
The cartilage of Jacobson, being trough-shaped with an upper
opening, it follows that the glands in the upper part of the wall
of the organ of Jacobson, viz. those, the ducts of which open in
the upper sulcus, form an unbroken continuity through that
opening with the serous glands of the mucous membrane covering
the septal cartilage. These points, ¢.¢. the presence of a gland-
fold in the lateral wall, the continuity of the glands of the
organ of Jacobson with those of the mucosa covering the septal
cartilage, together with the above-mentioned trough-shaped
nature of Jacobson’s cartilage, form the chief differential
characters by which to distinguish at once the sections placed
through the most anterior portions of the organ of Jacobson
from those made of the rest, except the posterior extremity, which
will be considered presently.
In some places the median wall of the organ of Jacobson contains a
few alveoli of serous glands ; these are evidently outrunners from the glands
of the lower wall, that is, those opening into the lower sulcus.
In these respects, then, the organ of Jacobson differs consi-
derably from that of the guinea-pig, as described in my former
papers, while it approaches to a certain limited extent that of
the typical organ of the mammal, as described by Gratiolet, and
that of the sheep, as described by Balogh. Gratiolet! speaks of
the upper wall as possessed of a “ bourrelet saillant,” and con-
taining numerous glands, but it is quite clear from his descrip-
tion that this ‘‘bourrelet saillant” is not the same thing as our
“‘ slandfold,” since, besides its different position, he ascribes
it not to a separate group of glands, but to the glands in general.
He also speaks? “d’un grand sinus veineux qui régne dans toute
l’étendue du bourrelet.”’
RAEG,; Pe 205
7L.¢., p. 21.
560 DR. E. KLEIN.
Balogh! says that in the sheep’s organ there exists a “ gland-
projection” (Driisenwulst) in the mucous membrane of the organ
of Jacobson, which extends from the upper and outer parts of the
mucous membrane into the lumen of the organ of Jacobson.
The bourrelet of Gratiolet and the Driisenwulst of Balogh are
evidently the same thing, but they differ from the glandfold of
the middle of the lateral wall as described by me of the rabbit.
In the guinea-pig there is nothing of the kind, as I have pointed
out in my former paper.
In the posterior position of the organ of Jacobson we find
the following disposition of the several layers :—The median wall
in its sensory epithelium, and its numerous plexuses of olfactory
nerve bundles remains unaltered, so does the epithelium of the
lateral wall, the subepithelial layer, the glandfold, and the elastic
layer. The cavernous layer, however, becomes greatly increased
in thickness and extent, encroaching considerably on the lower
and upper wall; hence the glands opening into the upper suleus
appear very greatly diminished in numbers. The same is the
case with the glands opening into the lower sulcus ; these sooner
or Jater cease altogether.
At the very extremity of the organ of Jacobson we find the lumen
reduced to a minute opening; in the median wall we still find a
trace of the sensory epithelium, but soon this also disappears,
the lumen becomes circular in transverse section, and the epithe-
lium is altogether made up of columnar cells. In the posterior
extremity of Jacobson’s organ the lumen and the lining epithe-
lium in so far alter their position as they are now close to the
median labium of Jacobson’s cartilage, and they shift also a
little more in a downward direction (see figs. 8 and 9).
A plexus of thin olfactory bundles is still to be recognised in
the upper part of the median wall, but this latter is greatly
reduced in thickness. The glands opening into the upper sulcus
reach lower down than before.
Of a glandfold in the lateral wall, or of a subepithelial layer,
nothing is left; the lateral and lower wall are occupied by the
cavernous tissue, which possesses a considerable thickness, and in
which the bundles of non-striped muscular cells, running in
all directions, still form a conspicuous feature.
We see, then, that in all repects the organ of Jacobson of the
rabbit differs materially from that of the guinea-pig; the shape
and size of Jacobson’s cartilage, the disposition of the several
structures in the median and lateral wall, are quite different
in the two cases.
Before describing the minute structure of the different parts
' Lc, p. 457,
THE ORGAN OF JACOBSON IN THE RABBIT. 561
constituting the median and lateral wall of the organ of Jacob-
son, I will give here the results of measurements carried out in a
transverse section through the organ of Jacobson, such as is
illustrated in fig. 4, viz. at a point where the cartilage of Jacob-
son forms a complete capsule.
Thickness of Jacobson’s cartilage at the upper angle. . 056 mm.
” ” a at the lower angle. ROO 2050 95;
» Fe is in the middle of the lateral
wall 0225 4,
» : . in the middle of the median
wall. Ost as
Short transverse diameter, 7.e. across the middle of Jacobson’s
cartilage capsule, from side to side, inclusive of the thick-
ness of the cartilage of both the lateral and median wall . 1°295
Long transverse diameter, z.e. from the upper to the lower
wall, inclusive of the thickness of the cartilage of both the
upper and lower angle. wat SUMS
Thickness of the lower wall of the organ of of acobson, exclu.
sive of the epithelium lining the lumen . 0°225_,,
_ a epithelium at the lower sulcus . ‘ feign :,
* ie lateral wall in about the middle, exclusive of
the epithelium lining the lumen _.. Fee es
re os epithelium of the lateral wall . ; » O45 “>,
z3 Gs gland layer at the lower sulcus . O2on
- Pes sensory epithelium in about the middle of
the median wall, at a place where there is
in it a Jymph- -follicle 0-388 ,,
ss remainder of the mucosa of the med‘an wall Ubi eee
Long transverse diameter of the lumen of the organofJacobson 0°45 _,,
#OHES5
2? 33
Short ” ” ”
The measurements taken from a section such as is illustrated
in fig. 11 are:
Thickness of Jacobson’s cartilage in the middle of the lateral
wall . - 0148 mm,
” 99 5 in the middle of ‘the median
wall. sigan,
t R! * in the middle of the | lower
wall. OLS. ves
» ee “ at the extremity of the
upper labium : Ue a ae ae
Diameter from the extremity of the median labium to the
lower wall’of the Sane inclusive of the thickness of this
latter. a eRab es;
In a section further back, e 4g: one shown in fig. 7, this dia-
meter increases to . 5°12
Diameter from the extremity of the lateral labium to the
middle of the lower wall of the cartilage, inclusive of the
thickness of this latter . : 2'2
Transverse diameter of the opening between the extremity of
the lateral labium, right across to the middle of the median
labium of Jacobson’s cartilage . : : s : . O45
562 DR. E, KLEIN.
Thickness of osseous lamina outside the lateral labium of
Jacobson’s cartilage ; P é 4 : - . 0°05 mm.
Long transverse diameter of the lumen of Jacobson’s organ . 0°6875 ,,
Short ” ” 3 ee) ” . 07135 ”
Short transverse diameter of the whole organ of Jacobson,
exclusive of the cartilage, measured across the middle on SABE Gs
Thickness of the epithelium of the lateral wall . : , OD4S
Greatest thickness of the glandfold, inclusive of epithelium . 0°1656 ,,
Greatest height diameter of this glandfold, ¢.e. in an upward
and downward direction . j : 5 . ; . 0852. .
Thickness of the elastic layer ‘ ; ; . 0°008 to 0016 _,,
= ts cavernous layer in the middle of the lateral
wall. i : : ; : . O338 5,
ra és mucous membrane of the median wall, ex- ]
clusive of the sensory epithelium . «> O335'es,
“s sensory epithelium : . 0°136 to 0'°225 ,,
rF) -
Transverse diameter of a large olfactory nerve trunk in the
median wall rp ; : 0144 by 0216 _,,
Diameter of a lymph-follicle within the sensory epithe-
lium . : : : . . ‘ : . 0194 by 0252 ,,
In addition to the description given in the preceding pages of
the structure of the different parts constituting the wall of the
organ or tubes of Jacobson, we have now to state various points
of detail not yet mentioned.
1. As regards the lateral wall.
(az) As mentioned above, the epithelium lining this is strati-
fied columnar, being composed of three layers of cells ; a superficial
layer of conical or cylindrical cells, each with an oval nucleus ; a
deep layer of inverted conical cells, z.e. cells whose base is fixed
on the subepithelial layer and whose pointed process is directed
towards the free or inner surface, each of these cells possess a
more or less spherical nucleus. Between these two layers of cells,
especially between the superficial cells, there is a middle layer of
cells composed of spindle-shaped cells, each with an oval nucleus.
The nuclei of the superficial cells are the largest. In specimens
hardened with spirit, the nuclei of the superficial conical cells
and of the spindle-shaped cells appear as if situated in the same
layer, and it then appears as if the epithelium were made up of
two layers only.
On the inner or free surface of the superficial cells is a distinct
and sharp boundary line, but there are no cilia projecting beyond
this boundary line. In the guinea-pig the superficial cells of
this epithelium possess cilia, as I have pofnted out in my first
paper, and I have then doubted Loewe’s! assertion as to the non-
existence of cilia on this epithelium in the rabbit’s organ. But
I now find that in all my specimens of the rabbit’s organ, be they
prepared with osmic acid, Miiller’s fluid, chromic acid, or spirit,
1 ¢ Beitr, zur Anatom. d. Nase und Mundholle,’ Berlin, 1878.
THE ORGAN OF JACOBSON IN THE RABBIT. 568
taere are never any cilia to be met with onthe surface of the
epithelium, and in this respect there does really exist a remark-
able difference between the rabbit’s and guinea-pig’s Jacobson’s
organ.
The epithelium of the lateral wall now under consideration is
always infiltrated with lymph-corpuscles, each with two or three
small nuclei ; these cells evidently migrate from the subepithelial
layer into the epithelium; they are found in all parts of the
epithelium.
(4) The subepithelial layer contains always a great number
of lymph-corpuscles, both in the glandfold and beyond it ; the
lymph-corpuseles are relatively large cells, each of them possessed
of a well-formed cell body. Where they are crowded together
they appear pressed against one other, and therefore more or less
polyhedral in outline.
(c) The elastic layer is composed chiefly of networks of fine
elastic fibrils extending in a direction parallel to the long axis of
the organ. ‘This layer, increases in thickness (to almost double)
as we pass backwards ; it is always very conspicuous in transverse
sections stained with dyes, since its bright fibres do not stain,
and therefore contrast well both with the subepithelial layer and
with the cavernous layer outside. ‘The elastic layer is evidently
the layer in which the muscular fibres of the cavernous layer
insert themselves. b
(2) The cavernous layer. This is the most conspicuous part of
the lateral wall. As mentioned above, it increases both in thick-
ness and breadth as we pass backwards (compare figs. 4 to 9).
Tts venous sinuses take up a plexus of small vessels, chiefly veins,
situated close to the elastic layer. The sinuses extend in a longi-
tudinal direction and are separated from one another by, or rather
are embedded in a tissue, which consists pre-eminently of mus-
cular substance. ‘This is arranged in bundles of various sizes,
directed chiefly ina radiating manner from the periphery of the
organ, 7.¢, from the outer wall of Jacobson’s cartilage towards
the lumen of the organ, and connected into plexuses. Between
these bundles we meet always a few bundles running in an oblique
or even longitudinal direction. In preparations prepared with
spirit the muscular tissue does not differ from non-striped mus-
cular tissue, but in osmic acid specimens, hardened afterwards in
chromic acid, the elements of this muscular tissue appear ma-
terially to differ from ordinary non-striped muscular tissue. We
find, namely, that the individual elements are twice and three
times as thick as ordinary non-striped muscle ceils ; that they are
composed of coarse fibrille, and that they appear much longer
and each to possess a number of nuclei ; further, that they appear
as if branched and connected into a network, so that they resemble
564 DE, E. KLEIN.
the muscular fibres of the heart much closer than ordinary non-
striped muscular cells. Whena bundle of the muscular fibres of
the cavernous layer is viewed in cross section the individual small
elements appear in their size and structure very much like
the muscular fibres of the heart.
In the matrix of the cavernous tissue may be met with small
and large bundles of nerve fibres chiefly following a longitudinal
course; in most cases the nerve fibres are medullated fibres, but
there are here and there bundles to be seen, the greater majority
of whose nerve fibres are non-medullated.
The outer boundary of the cavernous layer and the outer in-
sertion of its muscular bundles is formed by fibrous tissue
intimately connected with the perichondrium of Jacobson’s
cartilage.
(e) As regards the glands occupying the upper wall, z.e. those
opening in the upper sulcus, as well as the glands in the lower wall,
z.e. those opening into the lower sulcus, their structure, position,
and change in amount has been mentioned above, and is easily
understood from an inspection of the figures. The epithelium of
the ducts of both groups at their mouth forms one continuity with
the epithelium of the lateral wall, but is quite distinct from the
sensory epithelium; the same relation has been pointed out in
connection with the guinea-pig’s organ, where it was shown that
these ducts form in reality the boundary between the epithelium
of the lateral wall and the sensory epithelium, lining the median
surface of the lumen. So it is also in the rabbit; the two epi-
thelial structures, 7.¢. the epithelium of the lateral wall and the
sensory epithelium being well marked of from one another, and
the mouth of the ducts of the serous glands, both at the upper
and lower sculcus form the boundary between them.
2. The median wall.
The sensory epithelium consists, like that of the guinea-pig,
of two distinct strata—a superficial one composed of thin conical
spindle-shaped or cylindrical epzthelial cells, each with an oval
nucleus.
The cells forming this stratum vary from one another in this
respect, that the nucleus does not lie in all cells at the same level,
but is placed at different depths, so that, taking this stratum as
a whole, it appears to contain several layers of nuclei; generally
there are between three and five such layers. ‘The nuclei are
oval, some more elliptical than others; they stain always readily
in dyes, and hence they are very conspicuous in specimens so
stained.
The part of the epithelial cell between the nucleus and the
inner or free surface varies between 0°012 and 0:016 mm., and
it appears clear and longitudinally striated. On the free surface
THE ORGAN OF JACOBSON IN THE RABBIT. 565
it appears limited by a membranous structure, similar to the
limiting membrane of v. Brun in the olfactory organ.
The thickness of the layer containing the oval nuclei of these
epithelial cells is between 0°027 and 0:028 mm.
The size of these nuclei is 0°0054 by 0°0072, or 0°:0036 by
0°009 mm.
Underneath the epithelial cells, or rather underneath the nuclei
indicative of them, follows the deep stratum or the stratum of the
sensory cells. These cells are spindle-shaped or multipolar,
possessed of a cell body of clear, granular-looking substance,
and including a spherical nucleus, the size of which is about
00072 mm. ; being spherical these nuclei are therefore larger
than the oval nuclei of the ‘epithelial cells.” Besides,
the nuclei of the sensory cells are more transparent and less
stained in preparations stained with hematoxylin, and they
include a beautiful uniform network, or in some cases a convolu-
tion of fibrils. :
In a preparation hardened with spirit and stained with log-
wood the contrast between the two strata, z. ¢. the stratum of
the epithelial cells with deeply-stained homogeneous nuclei, and
the stratum of the sensory cells, with the large clear spherical
nuclei, is very great indeed, and no one looking at such a speci-
men can for a moment fail to see it. The number of sensory
cells, or their nuclei indicative of them, differs in different parts ;
it is greatest in about the middle of the median wall, and de-
creases towards the upper and lower sulcus. The greatest thick-
ness of the stratum of sensory cells is about 0°18 mm., and the
greatest number of nuclei, from the superficial stratum to
the subepithelial layer, in a vertical direction, is about eight
or ten.
The boundary of the sensory epithelium towards the sub-
epithelial mucosa is not well defined, the sensory cells Jdeing
prolonged singly or in small groups into the mucosa. This fact
does not come out so well in spirit preparations, but is distinct
in specimens prepared in Miiller’s fluid. In these latter the
deepest sensory cells, and especially those that extend into the
mucosa, appear larger in the amount of the cell protoplasm than
the more superficially situated sensory cells.
Everywhere the cell body is very distinct, owing to its rela-
tively large size, and when isolated appears, as in the guinea-
pig’s organ, spindle-shaped or multipolar. The processes, like
those of the sensory cells in the olfactory nasal membrane, may
be distinguished as an outer process, extending between the
“epithelial cells” to the surface, and one or more inner ones
passing downwards, 7.¢. into the depth towards the mucosa.
I have described this in my former paper in connection with
VOL, XXI,—NEW SER. PP
566 ; DR. E. KLEIN.
the organ of Jacobson of the guinea-pig, and I have there also
referred to the assertions and observations on these points by
Balogh! in the sheep’s organ, so that it is needless to enter into
this subject here again.
In the rabbit’s organ I have been able to follow what at first
I omitted to do in the guinea-pig’s organ, but what I have now
done also in this last named animal, viz. the distribution of the
olfactory nerve bundles and nerve fibres in the median wall, and
their relation to the sensory cells.
All along the inner surface of the median labium of Jacobson’s
cartilage we find olfactory nerve bundles following a longitudinal
direction ; spreading from behind toward the anterior regions of
the organ of Jacobson,” it is natural that we should find the
number of nerve bundles greater in the posterior than in the
anterior regions of the organ.
The transverse diameter of a large nerve bundle in the anterior
portion of the organ is about 0°144 by 0°216 mm. From these
nerve bundles, which, as mentioned just now, run in a longitu-
dinal direction in the outer parts of the mucosa of the median
wall, z.e. near Jacobson’s cartilage, numerous minute bundles
branch off, which run in an oblique direction towards the sensory
epithelium; they are very numerous, and by branching and re-
uniting form a plexus of small bundles of olfactory fibres occu-
pying the inner part of the mucosa of the median wall. The
nearer the sensory epithelium the smaller the branches and the
closer the plexus. This plexus, subepithelial plewus, extends
pre-eminently in a direction parallel with the short axes of the
organ of Jacobson. The ground substance of the mucosa in
which this plexus is embedded is made up of fibrous connective
tissue. The relation of this plexus to the sensory cells is this:
those sensory cells which, as mentioned above, extend into the
mucosa, are situated in the meshes of the plexus, but are very
closely applied to the branches of it, and from what I have been
able to make out in thin sections appear to become continuous
by their deep process with the nerve fibres in such a way that the
process constitutes a primitive fibril of an axis-cylinder of the
nerve branch.
Yn the sensory epithelium the sensory cells appear all to be
contained in the meshes of a plexus of fibrillar bands, which appear
directly continuous with the branches of the subepithelial nerve
plexus. As is the case with the sensory cells extending into the
mucosa, so also with the other sensory cells, it can be ascertained
that with their deep process or processes they join as primitive
1 L.c., pp. 465 and 466.
2 See Gratiolet and Balogh on the general distribution of the olfactory
nerve brauch.
~
THE ORGAN OF JACOBSON IN THE RABBIT. 567
fibrils the nerve plexus. I have given an illustration of these
appearances in fig. 12, and from this it will be seen that in this
respect the relations appear very similar to those described by Max
Schultze and others of the olfactory nasal mucous membrane,
but different from what is maintained by the latest investigator of
this subject, viz. Cisoff. Both in teased and non-teased specimens
of vertical and horizontal sections I have convinced myself of the
continuation of the subepithelial plexus of nerve fibres as plexus
into the sensory epithelium, and of the intimate apposition of the
deep process or processes of the sensory cells to the plexus, from
whose fibrils they could not be distinguished either in aspect or
position.
The naso-lachrymal duct in the rabbit, in the whole extent of
of the organ of Jacobson, is considerably larger than that of the
guinea-pig. or some distance anterior to the commencement
of the organ of Jacobson the naso-lachrymal duct is seen on each
side in the lateral wall of the nasal furrow, inside the cartilage,
forming the support of this latter between it and the surface
epithelium. In a section a little way further behind, like that
shown in fig. 1, the naso-lachrymal duct is seen outside the car-
tilage plate, mentioned in the introduction as the lower limb of
the cartilage, forming the support of the superior concha.
This changed relation between the naso-lachrymal duct and the
cartilage is not due to any change in position of the naso-
lachrymal duct, but to the fact that, as mentioned above, there is
a small cartilage plate present in the most anterior parts which is
not continued as far as the section represented in fig. 1; and, on
the other hand, the lower cartilage limb shown in this figure is
not present yet in sections anterior to the one shown in this same
figure.
Behind the section represented in fig. 1, until the disappearance
of the cartilage in the lower concha (fig. 3) the naso-lachrymal
duct retains the same position as before, viz. outside the cartilage.
It is situated just in the angle formed by the lower limb and
lateral limb of the cartilage forming the support of the lateral
wall of the nasal furrow. Compare figures 2 and 3.
Behind the mouth of the organ of Jacobson, the naso-lachry-
inal ducts are seen at the roots of the plicated part_of the inferior
concha between its osseous support and the alveolar process of
the upper maxilla (see fig. 4).
In the region of the posterior part of the organ of Jacobson
the naso-lachrymal duct changes slightly its position, inasmuch
as it descends a little lower down, 7.¢. nearer to the lower nasal
furrow.
As regards the shape of the naso-lachrymal duct, its cross
568 DR. E. KLEIN.
section appears in all preparations more or less oval, but is more
flattened from side to side anterior to the organ of Jacobson.
As regards the size, it appears greatest in about the region of the
mouth of the organ of Jacobson; anteriorly and posteriorly of
this it appears to decrease in size.
The following are the measurements of its lumen only, ante-
rior to a point shown in fig. 1:
The short transverse diameter ; : : . 0135 mm.
The long ¥ ‘ : : : «) ee os
At a point represented in fig. 1:
The short transverse diameter F é : . 01385 mm.
The long PS a : : , « OF8752,
A little behind this point, but before the mouth of Jacobson’s
organ is reached :
The short transverse diameter varies between . . 0°56 and 0°68 mm.
The long transverse diameter between. ; « 24S ai Si
In the region of the middle of the organ of Jacobson the naso-
lachrymal duct becomes again smaller, as is shown by the following
numbers :
The short transverse diameter varies between . . 038 and 06 mm.
The long transverse diameter between ; « LOL Ba eee
As regards the structure of the naso-lachrymal duct it is
everywhere the same:
1. The stratified columnar epithelium lining the lumen is of the
same nature as that described of the guinea-pig; the thickness
of the epithelium varies between 0°048 and 0:068 mm.
2. This epithelium is placed, just as was the case in the guinea-
pig, on a thin subepithelial layer infiltrated with lymph-corpus-
cles. In many places there are large lymph-follicles present in
the wall of the naso-lachrymal duct; these lymph-follicles have
their seat really in the subepithelial layer, and extend from here
both into the epithelium and in the outer parts of the wall of the
duct. Between more or less well-defined lymph-follicles and
diffuse adenoid tissue infiltrating the subepithelial layer are
all gradations. The diameter of a medium-sized lymph-
follicle, such as is shown in fig. 14, amounts to about 0°45 mm.
The adenoid tissue of these lymph-follicles penetrates into the
surface epithelium to the extent of the disappearance of this
latter at these places, just as is the case in other places where
lymph-follicles reach to the surface, e.g. Peyer’s patches of the
intestine, tonsils, and pharynx, &c.
But independent of the lymph-follicles, the adenoid tissue, at
any: rate the lymph-corpuscles and capillary blood-vessels of the
THE ORGAN OF JACOBSON IN THE RABBIT. 569
subepithelial layer, extend into the epithelium in many places in
a more or less uniform manner. ‘This is evidently analagous to
the fact described of the naso-lachrymal duct of the guinea-pig,
viz. an extension of capillary blood-vessels and nucleated cells
from the subepithelial layer into more or less well defined cavi-
ties in the epithelium. In the rabbit the intraepithelial spaces
containing the capillary blood-vessels and lymph-corpuscles do
not appear to be of this same well-defined nature.
3. Outside the subepithelial layer is a plexus of smaller and
larger veins, running chiefly in a longitudinal direction, and a
few arterial branches also extending in a longitudinal direction.
The tissue in which these vessels are embedded is a very loose
connective tissue infiltrated with numerous lymph-corpuscles.
As was pointed out in my former paper, Henle! already de-
scribed the occurrence of lymphatic tissue in the wall of the
naso-lachrymal duct of man.
The last point that I wish to describe here are the structure
of the mucous membrane lining the lower nasal furrow, and
covering the inferior turbinated bone, and the nasal septum in
the region of the organ of Jacobson.
In the most anterior portion of the nasal cavity, anterior to the
part illustrated in section, fig. 1, the epithelium covering the free
surface of all the above regions, viz. the nasal furrow, turbinated
bone, and nasal septum, is stratified pavement epithelium ; the
subepithelial connective tissue is infiltrated in many places with
lymph-corpuscles ; rudiments of papillee are present in the region
of the lateral wall of the nasal furrow.
The mucosa contains serous glands only over the inferior
concha. But there is everywhere an indication of venous plexuses,
situated in the superficial part of the mucosa, and extending
more or less parallel to the long axis of the nasal organ ; these
plexuses are well developed in the upper part of the septum and
in the inferior concha.
A little further behind, e. g. in fig. 1, the epithelium lining the
nasal furrow and the nasal septum is still stratified pavement
epithelium, but the epithelium covering the surface of the infe-
rior concha is already stratified columnar, the superficial cells being
ciliated. Numerous serous glands in the deeper layer, and very
rich plexuses of venous vessels in the superficial layer, are con-
tained in the mucosa of the inferior concha, and in a limited
degree also in the mucous membrane of the nasal septum.
In a place, of which fig. 2 is a representation, the lower nasal
furrow alone is lined with stratified pavement epithelium, all the
' « Hingeweidelehre,’ ii, p. 713.
570 DR. E, KLEIN.
other parts with stratified columnar cells, of which the super-
ficial layer is made up of ciliated cells, with the usual goblet
cells amongst them. The subepithelial layer contains numerous
lymph-corpuscles and a rich plexus of veins; the deeper layer
of the mucosa includes serous glands, forming a continuous
layer in the mucous membrane of the lower concha and in that
of the upper part of the nasal septum ; but they are scarce in
the lower part of the latter, and are altogether absent in the
mucous membrane of the lower nasal furrow.
The same relations obtain past the mouth of Jacobson’s organ
until the part is reached which is illustrated in fig. 4, ze.
showing Jacobson’s cartilage a closed capsule, except that the
mucous membrane covering the lower part of the nasal septum
contains very numerous serous glands; the epithelium lining the
lower nasal furrow is still stratified pavement epithelium.
A little further back, viz. where Jacobson’s cartilage has
assumed the shape of a trough (see figs. 5 and 6) with a long
median labium, also the epithelium lining the lower nasal furrow,
i.é. the concave surface of Stenson’s cartilage, is stratified columnar,
the superficial cells being ciliated, with the usual goblet cells
amongst them.
The thickness of this ciliated columnar epithelium is the
same as in other parts of the nasal cavity, and amounts
to about 0°:086 mm., exclusive of the cilia, which are about
00072 mm. long.
The serous glands in the mucosa of the lower part of the nasal
septum have now greatly increased, and, as has been pointed
out before, form a continuity with the glands of the organ of
Jacobson. ;
Of interest is the occurrence of diffuse adenoid tissue, and of
smaller and larger lymph follicles, isolated and in continuous
patches in the mucous membrane lining the concave side of
Stenson’s cartilage, as is shown in figs. 6 and 7.
The diameter of a well-defined lymph-follicle of the larger kind
varies between 0°216 by 0°25 mm., and 0°3 by 0°45 mm.
The extension of the adenoid tissue of these lymph-follicles
into the epithelium of the surface is the same as described above
of the lymph-follicles of the naso-lachrymal ducts.
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 57]
On the FurtHER DEVELOPMENT 0f WELWITSCHIA MIRABILIS.
By F. O. Bowsr, M.A., Camb., Assistant to the Professor
of Botany in University College, London. With Plates
XXXII and XXXTIT.
Since the publication of my paper ‘‘ On the Germination and
Histology of the Seedling of Welwitschia mirabilis” (‘ Quart.
Journ. Micr. Sci.,’ Jan. 1881), I have been put in a position to
study the structure of older plants, some specimens of these
having been supplied to me from the Kew collections, others
being kindly presented by Chev. D. J. de Nauet Monteiro. It
is the object of the present paper to describe the structure of
these older plants, and to show how it corresponds with that of
the young seedling as already described.
Before proceeding to this I must put on record information
received from Chev. Monteiro by letter. In plants of Welwits-
chia, which he has cultivated for three to four years, he tells me
that in one case “the first pair of leaves (or cotyledons) have
dropped off, one plant has one still on, and the remainder have
them still.” Further, he states that while they remain the
cotyledons do not change or grow; that as the stem enlarges
they become ‘jagged at the base, and on dropping they leave a
tumid scar, observable in the dried specimens as a circle under
the true leaves. In the older specimens it is so torn up that you
might take it for part of the cortical integument, unless you were
aware of the circumstances.”” These observations of Chev. Mon-
teiro supply us with the direct proof that the cotyledons wither,
and since there has never been observed a further development
of leaves of the main axis after the first plumular pair, we may
conclude that the latter are the leaves which remain persistent
throughout the life of the Welwitschia plant (cf. ‘ Quart.
Journ. Micr. Sci.,’ Jan. 1881, p. 29.) ;
Root and Hypocotyledonary Stem.—Hzxternal Characters.
The primary root of the seedling has already been described as
attaining a length of four to five inches without branching (es:
p- 19). In a letter Chev. Monteiro describes older plants as
developing a tap root ‘about eighteen or twenty inches in
length ;” after attaining this length the root branches repeatedly.
This was the case in the plants four months old which he sup-
plied to me. In external appearance the young roots present no
peculiarity. The roots of plants of medium age are, however,
572 ¥, 0. BOWER.
covered with a thick fluffy layer of tissue (effete corky tissue) of
a light yellow colour. This gives place in still older plants to a
darker and even black covering of greater strength and hardness.
These remarks apply also to the lower part of the hypocotyle-
donary stem. ‘The fluffy layer, being very friable, could not
easily be cut into sections by the razor; it will therefore not be
represented in the figures of sections accompanying this paper.
Internal Structure.—Root.
It was shown in my former paper (p. 25) that the cortical
tissue of the root, being cut off from physiological connection
with the central cylinder, ceases to grow, and is thrown off, so
that the older root consists of tissues derived only from the cen-
tral cylinder. We will now trace the further development of
that cylinder. Its periphery (as seen in fig. 22, 1.¢.) is oceupied
by a formative tissue derived from the pericambium. This gives
rise to a constantly and successively renewed cork tissue, which
is always to be found covering the root externally. Beyond its
presence it is not of any special interest; we may, therefore,
pass on to the consideration of the internal tissues.
In the specimens described in my former paper the fusion of
the diarch xylem system at the centre of the root was not
observed (1. c., p. 25, fig. 22). The two xylem masses were in
all cases separated by a parenchymatous tissue. It is true Ber-
trand (‘ Ann. d. Sci. Nat.,’ série v, tom. xx, p.9) has described
the central fusion of the xylem masses of the lateral root- of
Welwitschia, but the question as to the main root still remained
open. On comparison of older plants, however, it appears that
in the main root, for a short distance below the transition from
stem to true root, such a fusion does not occur, the centre of the
transverse section being permanently occupied by a mass of
parenchyma. As this tissue bears an important relation to the
further development of the part where it occurs, it will be
again referred to later (cf. fig. 22 of first paper, which was
taken at a point close below the feeder). In the lower portion
of the root a complete coalescence of the two originally separate
xylem masses takes place, so that a single plate is formed; the
junction is followed by a further development of xylem at the
central part of each side of the plate, produced by an active
cambium layer, which. lies between the primary phloem and the
xylem plate. The secondary xylem thus produced appears as a
narrow band on each side of the xylem plate, the two bands being
separated laterally from one another by very broad parenchyma-
tous rays. ‘The whole xylem system thus produced attains a
stellate form (fig. 1.). Thus far the structure of the root of Wel-
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 573
witschia corresponds to that of Ephedra (cf. Van Tieghem, La
Racine, p. 211).
Meanwhile a further development has been going on in the
parenchyma which surrounds the vascular tissues: this results
in the formation (a) of a number of irregularly arranged spicular
cells (sp. c.), whose axes are parallel to the longitudinal axis of
the root ; (4) of long sclerenchyma fibres with no crystals in their
walls (se/. 7., cf. Hooker, l.c., p. 15). The spaces between these
are filled with thin-walled parenchymatous tissue, whose cells
retain their cell nature, and play an active part in the further
development (cf. below). At the periphery of the section lies
a layer of cork derived from a phellogen layer, as already
described. Since the same is the case in sections from older
roots, the fact will not be again mentioned. It may be noticed
that the cork in fig. 1 has at certain points attained a considerable
thickness ; this corresponds to the fluffy layer already mentioned.
No secondary free vascular bundles are to be seen in fig. 1,
which represents a section cut far down the root of the youngest
plant in the Kew collections. Thus far the structure presents no
great peculiarities. The same root was, however, cut about one
inch further from the apex, and by comparison of a series of
sections, the first secondary bundles were observed to originate in
the following way :—One of the cambian bands becomes laterally
extended (fig. 11., 1), then a plate of parenchymatous tissue is
intercalated between the extension and the main mass (fig. 11, ii.).
A separate bundle is thus formed by branching of the main
bundle ; it is, therefore, a direct derivative of it, and does not end
“blind” (cf. De Bary, ‘ Vergl. Anat.,’ p. 303, &.). As the
new bundle pursues its course up the root it leaves its original
position relative to the main bundle system and takes a spiral
course till it is placed opposite to one of the protoxylem masses
(fig. 11, 41, 4,). A similar development goes on at the opposite
side of the root, and a symmetrical arrangement is thus attained.
It must, however, be remarked that the central bundle system
of the roots of Welwitschia is not always arranged as regularly
as here described, though this seems to be the typical arrange-
ment.!
This arrangement of the central vascular bundles of the root
is well seen in the section represented in fig. 1v. This was taken
at a point far down the root of the plant (fig. 11). This root
1 The description which follows is mainly derived from the study of one
plant which was handed over for dissection from the collections at Kew.
It is represented in outline in fig. 111, i, ii, From a comparison of it with
other rather younger plants, it is seen that the swelling of the stock starts
near the top, and proceeds downwards, the lower limit of the swelling
being pretty strongly marked, as seen in fig. 111, i.
574 F. 0. BOWER,
being much older than those before examined, the bundles of the
central system are further developed; it will be seen, however,
that they correspond exactly in their arrangement to the descrip-
tion given above. ‘The protoxylem masses can still be recognised
though the protophloem masses cannot be traced. Around the
former are grouped symmetrically four large vascular wedges, two
of which are connected centrally with one another; these are
derived directly from the activity of that cambium layer which
appears between the protophloem and the primary xylem plate,
those which alternate with them having been derived from them
by branching, as above described. It is true there are frequent
deviations from the type, due to the sinuous course pursued by
the bundles of the centrai group, and by their frequent anasto-
mosis both with one another and with the members of the
later developed peripheral system; but the tendency is to return
after these irregularities to the typical arrangement. Though
in older roots the bundle system becomes complicated by the
formation of large numbers of peripheral bundles, still as a rule
the centre of the root is occupied by the original fourfold group.
Since these bundles, and in fact all bundles of the root of Wel-
witschia, remain “ open” for a long time, they attain in old roots
a very considerable size. The discrepancy of this description
with the figures and account given by Hooker depends upon the
fact that the xylem is there omitted, while the phloem is repre-
sented as the whole bundle (cf. also De Bary, ‘ Vergl. Anat.’
. 633).
: On ey a the arrangement of the bundles of the central
system comparatively, we see that there is here in the root of
Welwitschia a case similar to that in the stems of many Dicoty-
ledons, in which it is found that the broad medullary rays are
traversed by intercalary bundles (Zwischenstringe, cf. De Bary,
‘Vergl. Anat.,’ p. 408, &c.) ; these keep up a vascular connection
between the primary bundles on either side of theray. We have
as the counterpart of these intercalary bundles those branches
(fig. Iv, 4,), which pursue a sinuous course along the very broad
medullary rays of the root of Welwitschia, and which from time
to time fuse laterally with the primary bundles.
As the central group develops, there appear in the peripheral
part of the root a number of fresh bundles, which, though not
disposed regularly in rings, still show a tendency to that
arrangement. Such bundles are to be seen in fig. Iv, per. bum.
As to their ending I cannot speak definitely, but this much is
certain, that whereas I have often been able to observe anasto-
mosis between members of this peripheral series, as well as between
them and the central group, | have never obtained evidence of
their ending “blind.” Having the analogy of the central group
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 575
before us, we may therefore consider it as probable that the
peripheral series is connected terminally with the central group ;
that is, that the bundles of the root form a single system having
a common origin.
To the question of the communication between the bundles of
the central group and those of the peripheral system, I have paid
special attention, since Bertrand (‘ An. d. Sci. Nat.’ série v, vol. xx,
p- 10) asserts that the latter series are always separated from
the central system by fundamental tissue. I have, however, been
able to satisfy myself that the contrary is the fact, and by com-
parison of long series of transverse sections, I have succeeded in
tracing the passage of branch bundles from the central group to
the peripheral series. As to the lateral communication of dif-
ferent members of the same series, it occurs so frequently that it
can be observed in any series of transverse sections ; moreover
tangential sections demonstrate that the bundles of either series
form a cylindrical network. It is owing to the irregularity of
the frequent anastomosis that the central series, as well as the
peripheral, show those varieties of arrangement to which they have
already been described as being subject.
As the root increases in age its bulk also increases. This is
due partly to growth of the old bundles and formation of new
ones, partly to growth of the tissues in which the bundles are
embedded.
It has already been stated that the bundles of the central group
remain “ open” and increase in size, while fresh series of open
peripheral bundles are formed outside them. The disposal of the
members of the later-formed series is more regular than that of
those earlier developed, so that in old roots the appearance is
presented of a number of definite rmgs of bundles surrounding
others less regularly arranged. The new bundles are formed by
active division at certain points in the parenchymatous “ground
tissue.” Fig. v represents the points of origin of three new bundles
of a‘peripheral series. Though at first sight this figure gives the
idea of a definite cambium layer in which the new bundles appear
at certain points (as in the monocotyledonous stems with second-
ary thickening), it will be seen, on observing it more closely, that
at the limits of the figure the tissues bear traces of less active
division, the fact being that the activity is specially localised
around the point of origin of new bundles (cf. infra).
The arrangement of the other tissues of the older root now
demands further attention. The spicular cells seem here, as in
other parts of the plant, to be pretty uniformly distributed ; they
are more numerous towards the periphery of the root. Fresh
spicular cells may be formed from single cells of the parenchyma
at any point outside the vascular bundles; occasionally they are
576 F. O. BOWER.
even to be found embedded in the secondary phloem, in which
case they must have originated from cells of the bast parenchyma,
or directly from the cambium. The longitudinal axis of the
spicular cells is usually, but not always, nearly parallel to the
axis of the root. Sclerenchyma fibres are also to be found in
considerable numbers in the old root: they lie scattered singly in
the parenchyma, chiefly around the periphery of the vascular
bundles ; they take a sinuous, longitudinal course. Gum pas-
sages are also to be found in the roots: they appear irregular in
their distribution (fig. 1v).
The parenchyma in which all these several tissues are em-
bedded deserves special attention, since many of the abnormalities
of structure of the root and also of the stem of Welwitschia are
the outcome of its peculiar properties. The most remarkable of
these is its constant capability of cell division (Halb-meristeme-
tisch, De Bary, ‘ Vergl. Anat.,’ p. 634). The parenchyma seems
in no living part of the plants which I have examined to have
passed over to the permanent condition ; it seems normally to be
subject during its whole life to occasional division. It is true
that the activity of this division is not uniform, but that it is
specially localised at certain points, such as (a), the base and sides
of the leaf groove (fig. x) ; (4) the point of origin of new vascular
bundles (fig. v) ; (¢) the phellogen layer; but that does not alter
the fact that cell division may and usually does occur (at least
in moderately young plants) more or less actively wherever there
is in stem or root a parenchymatous ground tissue. We shall
now be able better to realise what occurs when new peripheral
bundles are formed, as in fig. v. An active division takes place
at the point where the new bundle is to be formed; the surround-
ing tissue keeps pace with the radial extension thus produced,
but the activity is merely local; there is no tangentially conti-
nuous ring of activity dividing tissue, such as that in the mono-
cotyledonous stems with secondary thickening.
Though this activity of division is well marked in the paren-
chyma of the root, it is in the stem hereafter to be described that
it is most striking; and, indeed, the swelling of the stock, which
starts from the apex and proceeds downwards is mainly due to
this activity.
A further peculiarity of the parenchyma is this—that appa-
rently any cell may develop into a spicular cell or sclerenchyma
fibre, and that this development is not restricted to any particular
zone, but seems to be another proof of the general activity of
the parenchyma. We find spicular cells in very different stages
of development, occurring side by side, both in root and stem
(fig. xx). (For the development of the spicular cells, see below,
p. 590).
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 577
The lateral roots appear externally to the protoxylem masses,
and are produced by the activity of the pericambium only, the
cells of the bundle sheath apparently taking no part in the
process.
Transition from Root to Hypocotyledonary Stem.
We have found no difficulty in recognising the relation of the
structure of the older root to that of the young root, as described
in my former paper (cf. l.c., fig. 22). As we now proceed to
trace the transition from true root to hypocotyledonary stem, we
must bear in mind the structure of the corresponding part of the
young seedling as there described. It has already been shown
how in the lower portions of the main root the two originally
separate protoxylem masses unite centrally to form a single xylem
plate, but that for some distance below the point of transition
from root to stem this coalescence does not take place, the centre
of the root being occupied by a mass of parenchyma. Here, as
in other parts of the plant, the parenchyma retains its activity,
and is capable of increase. This may be observed in plants at a
comparatively early stage. In those sent me by Chev. Monteiro
(four months old), divisions in this medullary tissue were already
observable.
The course of the vascular bundles at the point of transition
from root to stem was traced carefully in the plant represented in
fig. m1, and the following description is based chiefly upon results
obtained from it :—The main root retains throughout its length
the same arrangement of its vascular system (fig. 1v), the only
change being that higher up (7.e. nearer the stem) ; the peripheral
system is more complicated. In the series of figures (v1, 1—6)
which illustrate the transition from root to stem, the younger
peripheral bundles, as well as the spicular cells and sclerenchyma
fibres, are omitted. In all cases the xylem is shaded, while the
phloem is left white. The numbered dotted lines in fig. 11
show the points at which the successive members of the series
fig. vi were cut.
If we compare fig. 1v with fig. vi, i, we see at once a difference
in the arrangement of the central vascular group. In the latter
figure it is divided into two parts by a plate of parenchymatous
tissue. The protoxylem masses can easily be distinguished (pr.
ry.). They have the same relative position as in fig. iv. Pro-
bably the fig. 22 of my former paper represents a section cut at
a corresponding point in a younger plant: since a central fusion
of the vascular tissues did not take place at this point in the
young root, the secondary products, as seen in the older roots,
also remain permanently separated by a plate of parenchymatous
578 Fr. O. BOWER,
tissue, which divides the central vascular group into two parts.
As we pass further upwards, the variation from the true root type
extends. In fig. vi, 2, we have a condition in which the proto-
xylem masses, though they are still only two in number, are
separated further from one another. This separation is due to
an active increase in bulk of the parenchymatous tissue origi-
nally lying between them. It will be noticed that the compo-
nents of each group tend to arrange themselves radially around
the protoxylem masses as centres.
As we again pass further upwards, at a short distance above
Section 2, each protoxylem mass is seen to divide into two (fig.
vit, 3), and at the same time each of the two groups of bundles
is divided by a plate of parenchyma into two, so that the central
system of bundles now appears arranged in four groups. Hach
of these includes one protoxylem mass, around which the other
bundles of the group tend to arrange themselves radially. It
will be noticed that the distance of the two pairs of protoxylem
masses in 8 from one another is greater than that of the single
mass in 2, while the whole section is elliptical in form. This is
doubtless the result mainly of the secondary activity of the
parenchyma so often alluded to. The number of peripheral
bundles is increased. Referring to fig. 111, it will be seen that
between the points 3 and 4 there occurs a sudden swelling of
the stock, hence the difference in area between 3 and 4 of fig. v1.
As they pursue their course upwards from 3, the four protoxylem
masses, with the groups of bundles surrounding them, separate
from one another till all four are at equal distances apart.
Meanwhile the bundles of each of the groups arrange themselves
nearly symmetrically round the four centres. The peripheral
bundles undergo frequent anastomosis at the point of swelling,
both with one another and with members of the four central
groups. A comparison of the sections represented in figs. v1, 3
and 4, shows that though the plant increases very largely in
thickness between the planes of these two sections, still the vas-
cular system does not become much stronger, but that the paren-
chyma increases very much in bulk. (N.B.—The bundles in fig.
vi, 4, are drawn rather too thick.) Here, then, we have to deal
with a more prominent instance of the effect of the activity of the
parenchyma. A comparison of fig. v1, 1—4, with fig. 15 eu
and fig. 22 of my former paper will throw some light on the
process of development. If allowance be made for the difference
of scale of the two series, it will be seen that a great increase of
bulk has taken place, and that in proportion to that increase in
bulk the original protoxylem masses have become separated fur-
ther from one another, i. ¢. that the increase is due not to a pro-
cess of external apposition of tissues, as would be the case if the
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS. 579
increase were due to a peripheral cambium layer, but to an
intercalary growth throughout the section.
From the figures of Hooker illustrating the structure of older
plants, and from observations of dissections of older specimens
with the naked eye, I conclude that after a certain time this
intercalary activity is diminished at the centre of the plant, and
becomes localised in the peripheral portions.
Up to fig. v1, 4, we have been able to trace the relationship of
the primary bundles of the seedling to the vascular system of
the older plant. We must, however, leave the study of the
upward course of the bundles at this point; before we are able
properly to estimate the relations of the vascular tissues of the
upper part of the stem, we must become better acquainted with
the external conformation of the apex of the plant.
Apex of the Plant.—Eaternal Characters.
From plants of three to four months growth I was able to
obtain early stages in the development of those two structures,
which he between the cotyledons; these were mentioned in my
former paper (p. 19, note), but I was not then able to make any
definite statement concerning them. .
If a thick horizontal section be cut through the apex of a
plant of about four months growth, it will be found to include
(1) the bases of the cotyledons, the two being distinguished only
by two indentations of the margin of the section; (2) the bases
of the plumular leaves (yp. /. fig. vit) ; (3) the apical cone of the
stem (ap.), which appears hardly any further advanced than in the
younger seedlings described in my former paper (fig. 15 a); and
(4) the two structures in question, which lie between the plumu-
lar leaves on either side of the apical cone (/.c., fig. vit). In this
figure they appear of unequal size; this appearance is, however,
due to the fact that the plane of section was not exactly horizontal
in the case figured. In reality they are as a rule nearly equal in
size. (Note.—Fig. 10 of former paper is an exception to this.)
I have observed no sign of fresh lateral appendages either on
them or on the apical cone, with the exception of the fertile
branches, the origin of which is clearly adventitious, and will be
dealt with later. As the plant increases in size these lateral
cones grow more strongly than the apical cone, and overtop it,
so that in the older plants they are the only prominent struc-
tures to be found between the plumular leaves (fig. 111, and fig.
10 of former paper). These two cones widen as the plant
increases in age and form the crown of the plant. In plants
with a crown of three inches in diameter it is possible still to
trace a division of the crown into two areas corresponding in
580 ‘ ¥F, 0. BOWER.
position to the original lobes ; but in plants above this size this
character is usually lost, since the comparatively small fissure
which marks off the two areas from one another is masked by
the much more deep fissure of the crown, which, as described by
Hooker (l.c., p. $), runs in a direction paralle] to the bases of the
plumular leaves of old plants. In all plants, however, of suitable
age which have passed through my hands, the same conforma-
tion appears between the plumular leaves. We may then con-
clude that the apical cone of Welwitschia ceases to grow either
apically or laterally, and that the crown is derived directly and
solely from two lateral cones arising on either side of the apical
cone between the plumular leaves; further, that these maintain
a constant increase in width throughout the life of the plant.
The question naturally arises, what is the morphological value
of the two lateral cones? I conclude, on the following grounds,
that they are morphologically axillary buds in the axils of the
cotyledons.
(a) Their position supports this view, if allowance be made for
lateral compression by the plumular leaves, to the development
of which every part of the plant seems to be subordinate. The
lateral cones do not appear to be genetically connected with the
apical cone of the plant.
(4) Such axillary buds are to be found in the axils of the
cotyledons of Ephedra.
(c) Their structure, when older, has very little resemblance to
a leaf (the alternative view being that they are a second pair of
plumular leaves).
(d) The development of axillary buds is the rule in the fertile
branches of Welwitschia, and this occurs in the axils of the jirst
pair of leaves of the male branch.
The position of the leaves and their insertion at the base of
the leaf grooves are facts already so well known that they need
hardly be again described. Reference need only be made to
figs. 111 and vii, in which the well-known arrangement will be
easily recognised.
Hypocotyledonary Stem and Apical Region.—Internal Structure.
We shall now be in a position to continue the study of the
course pursued by the vascular bundles as they proceed up the
hypocotyledonary stem. We have seen the central bundles
arrange themselves round four centres (fig. v1, 4), while in the
peripheral part of the section appear a number of small bundles,
which anastomose freely both with one another and with the
' As a parallel case to this is cited by Mr. W. T. Thiselton Dyer
Mora excelsa of British Guiana. |
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 581
members of the central groups. Successive sections higher up
the stem show a gradual deviation from this arrangement. ‘The
four central groups split up into smaller central bundles
(fig. vit, 5); these, however still retain a position obviously
related to four centres. Above fig. vir, 4, it was not possible to
identify the primary bundles. As they proceed again further up
the stem, the bundles nearer the centre of the transverse section
begin to rotate separately on their axes, so that each assumes a
position with its xylem directed towards the centre and its
phloem towards the periphery of the section (cf. the rotation of
bundles in the hypocotyledonary stem of the seedling; former
paper, p. 22). At the same time the courses of the bundles
diverge, so that the whole bundle system becomes separated into
(a) a group of bundles which arrange themselves into two wavy
nearly parallel lines, and which are clearly the bundles which
come in from the plumular leaves (blatt-spurschicht) ; this is
seen to be the case in fig. vi1, 6, where the section includes the
margins of the plumular leaves; (4) a central group of small
bundles, which will be afterwards seen to run up into the lobes
of the crown; and (c) a peripheral series, which are regularly
arranged with their xylem towards the centre and their phloem
towards the periphery. Between these various series are to be
seen bundles which pursue a horizontal course, and keep up con-
nection between them.
For the further elucidation of the bundle system of the apex
we must refer to longitudinal sections. Since the lobes of the
crown have a bundle system of their own, it is to be expected
that the arrangement of bundles will appear different according
as sections are made in a median plane (fig. 111, B), in which case
the central lobes would be only slightly touched, or in a tangen-
tial plane, which would pass through the lobe as in fig. 111, a.
Such sections are represented in fig. vir, a4, B. In both of these
may be seen the two deep leaf grooves, with the bases of the
plumular leaves still adherent. Between the two grooves
rise the lobes of the crown. In the one case (a) one of these
lobes is cut through longitudinally, in the other (8) it presents
its central edge. The dark shaded peripheral portions of these
sections represent the masses of brown corky tissue, which are
specially large at the upper part of the stock, and are produced
by the degradations of portions of tissue originally active. The
process of degradation extends as the plant becomes older, and
even vascular bundles are often to be found included in the effete
mass, especially in older plants. A similar degradation is also
to be found at the apex of the lobes of the crown. The limit of
the degraded tissue at the upper part of the plant is not marked
by any very definite cork layer specially developed ; it appears
VOL, XXI.—NEW SER. QQ
582 F. O. BOWER.
rather that a process of change goes on in the cell walls of the
tissues already formed, and extends gradually inwards, accom-
panied by loss of the cell contents.
From the bases of the leaves bundles are seen to enter the
stem (‘‘ blatt-spurschicht,” De Bary, ‘ Vergl. Anat.,’ p. 632.
** Vascular stratum,’’ Hooker). These pursue for a certain dis-
tance a nearly parallel course; later they break up into irregular
branches. ‘This is best seen in fig. vii1, B. This fact is easily
reconciled with what we have already seen in transverse sections.
In comparing the several figures it must be remembered that the
dotted line in fig. vii1, B, indicates the point to which the trans-
verse section, fig. v1, 6, corresponds: while the section, fig. v1,
5, is taken at a point some distance below the branching of the
bundles of the leaf trace (Blatt Spurbiindel). From these
bundles of the leaf trace branches are given off in different direc-
tions; for clearness sake these, and others which intertwine with
them, may be ranged into several categories according to the
direction of their course ; these categories merge, however, into
one another. ;
(a) Branches which run horizontally. These take a course
along the inner margin of the bundles of the leaf trace (fig. v1, 6)
and send out branches between these bundles towards the
periphery ; or they take a direct course between the bundles of
the leaf trace, and run out into the peripheral part of the stock ;
this is most common at the centre of the stock, fig. v1, B.
(2) Branches which ascend either (i) into the central lobes, or
(ii) into the upper peripheral parts of the stock (fig. vimt, a).
Lastly (c), there is a third series of bundles which are appa-
rently not in direct connection with the bundles of the leaf trace :
these run up the stem, and passing between the bundles of the leaf
trace (apparently without any anastomosis) continue their course
into the lobes of the crown. We have thus a direct vascular con-
nection kept up between the following several parts of the plant
(1), between the leaf and the peripheral part of the stock (2),
between the leaf and the lobes of the crown, and (3) between the
lower part of the stock and the crown. It will be seen later
that these connections are similarly kept up in the older plant.
The mutual vascular connection of different parts of the peri-
phery of the stock is also very complete. In fig. viii it is shown
that amastomosis of bundles in this part of the plant is frequent.
This is more evident in tangential sections at the periphery, and
more especially in old plants, where the bundles are seen to form
a most complicated and irregular network. In the special plant
under consideration (fig. 111) these ramifying branches collect as
they pass from the summit of the stock, so that they appear in
transverse section (fig. vi, 6) as a regular peripheral series. It
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 583
may be seen, in fig. vi11, how this happens. I have no evidence
of “blind” endings of bundles in this part of the plant, though,
owing to the great irregularity of course of the bundles, the proof
of such endings would be very difficult. It cannot, therefore, be
asserted that they do not exist (cf. ‘‘ Cycas,” De Bary, ‘ Vergl.
Anat.,’ 630).
In horizontal section the lobes of the crown present an appear-
ance as in fig. 1x, a, B, the former being a section near the base,
and the latter near the apex, of one of the lobes: Externally the
lobe is covered with epidermis; beneath this is a tissue capable
of division, in fact, this is the chief formative tissue of the lobe,
by means of which it increases in bulk (cf. cmfra). Vascular
bundles are scattered somewhat irregularly through the section,
but they are evidently arranged with relation to the centre, the
xylem being usually central. The peripheral bundles pursue a
less regular course than those nearer the centre ; they anastomose,
and run horizontally, &. These irregularities are again more
marked in the later developed bundles, which are formed as the
lobe increases in size. In large plants the course of the peri-
pheral bundles of the crown is very sinuous, and difficult to
follow (cf. zwfra). As before stated, the tissues at the apex of
the lobe suffer a corky degradation, which starts at the apex and
spreads backwards, including, as in the stock, not only paren-
chymatous tissue and spicular cells, but also vascular bundles.
We must now turn our attention to the région of greatest
vegetative activity, viz. the base of the leaf groove. Ifa longitu- |
dinal section be made through this, the whole mass of tissue is
found to be in a state of active increase. The direction of the
divisions is shown in fig. x, which represents under a higher power |
the area marked off (x) in fig. vii, a, and includes part of the
outer and inner lips of the leaf groove, together with the basal
part of the plumular leaf. The divisions in the tissues, beneath
the epidermis, which covers both lips of the groove, are most
frequent in a direction parallel to the surface, so that the chief
increase of bulk of tissue is in a direction perpendicular to the
surface. ‘The divisions in the tissues of the stock below the base
of the leaf groove are mainly transverse (as regards the axis of
the stock). A growth in length of the stock is thus effected.
The divisions at the base of the leaf itself are mostly in a similar
direction, that is, at right angles to the surfaces of the leaf;
an increase in length of the leaf structure is thus produced. The
divisions in these several parts being constantly repeated in the
same direction, the cells assume an arrangement in rows at right
angles to the direction of division. Such rows may be traced
distinctly throughout the greater part of the upper portion of
plants of the stage of development of fig. 111, and this shows that
584 F. 0. BOWER,
the greater part of their tissues have been or are concerned in a
similar division. Of course the rows of cells are not so clearly
marked in the older parts as at the base of the groove, where the
increase is most active: still they are easily traceable. I have
accordingly tried to represent, by means of lines in fig. vil, A,
the direction of these rows of parenchymatous cells (cf. Sachs,
‘Anordnung der Zellen in jiingsten Pflanzen-theilen, fig. 5).
Young spicular cells may often be found pushing their growing
ends between the young tissues (for their development, cf. infra).
Fresh vascular bundles also appear below the surface of the lips
of the groove, but their course is, as a rule, so tortuous that it —
can only be followed with difficulty. In the leaf, however, their
course being rectilinear, it can easily be traced (fig. x).
Cell division continues throughout the life of the plant in the
directions described, relatively to the leaf groove. The fresh
cells thus produced assume an approximately cubical form.
Bearing these facts in mind, we shall be able to understand how
- the further development of the plant proceeds. Since the divi-
sions in the tissue immediately below the epidermis of both lips
of the groove are mostly parallel to the surface of the groove, an
increase in bulk takes place, both in the crown and in the upper
part of the stock, mainly in a direction perpendicular to the sur-
face, z.e. both the crown and the upper part of the stock become
wider, at the same time the depth of the leaf groove does not
materially increase. We have seen that below the base of the
leaf groove the divisions are mainly in a direction perpendicular
to the axis of the plant; hence there results an increase in
length of the whole plant. But as the width of the crown
increases the activity of the central portion falls off, till finally
growth in length ceases in that part. The centre is, therefore,
overtopped by the more actively growing peripheral part. Hence
originates the cup-like form of the apex of old plants (ef.
Hooker’s figures). We have already an indication of this in
fig. x1. Finally, the divisions in the base of the leaf itself are
mainly transverse, and thus the growth of the leaf is strongest
longitudinally. For the verification of these several conclusions the
figs. x and x11 of this paper should be compared with the figures
of older plants given in Sir J. Hooker’s memoir. It will then
be easily understood how, by the increase in width of the lobes
of the crown, the bundles of the leaf trace (vascular strata of Sir
J. Hooker) of the plumular leaves, which are in the young plant
parallel to one another (fig. vir), become wedged apart. ‘As the
plant grows the angle between them constantly increases till, in
very old plants, the bases of the leaves almost lie in the same
lane.
; The section fig. x1 serves as an intermediate stage between the
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 585
plant represented in fig. 111 and the older plants described and
figured by Sir J. Hooker. On comparison it will be seen that,
though the relative positions of the several parts are slightly
altered by growth, the arrangement of the vascular bundles cor-
responds to that already described in the younger plant. We
are able here, as before, to trace a direct vascular connection
(1) between the leaf and the peripheral part of the stock, (2)
between the leaf and the crown, and (3) between the stock and
the crown. It may further he observed how in this older plant
the central bundles of the stock collect at some distance below
the entry of the leaf bundles into groups, which are identical
with the central vascular groups described in the lower part of
the stock of the younger plant (cf. fig. v1, 4,5). On the other
hand, the arrangement of the vascular bundles in fig. xt obviously
corresponds to that described by Sir J. Hooker in older plants.
We have here (using his nomenclature) the “ vascular stratum,”
consisting of the bundles which enter from the leaf, the “ ascend-
ing bundles,” which rise into the crown, and the “ descending ”
system, which passes into the stock.
The scheme of vascular arrangement proposed by Bertrand
(‘Ann. d. Sci. Nat.,’ série v, vol. xx, pl. 12, fig. 14) may be
here noticed. A glance at the figures illustrating this paper
will be enough to show that his scheme does not accord with my
observations.
In order to confirm our results we may turn to the appearance
presented by sections taken from an old plant in the plane of the
bundles of the leaf trace, so as to follow their course into the
stem (fig. x11). From these it is learnt that the leaf bundles do
not all run the same distance into the stem; that they vary in
this respect, some pursuing a direct course almost to the centre
before they pass out of the plane of section, others successively
less distances ; also, that there is a certain amount of regularity
in their arrangement, those which continue their course for a
less distance in the plane of section alternating with those which
pursue a direct course for a greater distance. Further, that
before leaving the plane of section the bundles usually divide,
and the branches often anastomose with bundles pursuing a
course perpendicular to them; or they may simply curve out of
the plane of section without anastomosis, and take a longitudinal
course upwards or downwards. Lastly, of the bundles, which
appear cut transversely in fig. x11, while some are connected by
anastomosis with the bundles of the leaf trace, others appear to
be quite separate from them; these are the bundles already
mentioned which pass between the bundles of the leaf trace, and
maintain a direct vascular connection between stock and crown.
It will be seen in fig. x11 that fresh bundles running perpendicular
586 F. O. BOWER,
to the section are formed at the peripheral part of the stem. 7. e.
nearer the shaded portion of the figure, which represents the
region of greatest vegetative activity at the base of the leaf.
On comparing the description now given for the older plant
with that before given for the younger plant, we must conclude
that the vascular arrangement corresponds in the two cases, and
that no fundamental change appears in the mutual vascular con-
nections as the development of the plant proceeds. The chief
difference lies in the fact that the bundles of the leaf trace do
not all proceed for an equal distance into the stem in the older
plant ; and this has an important bearing (1) upon the mode of
increase in number of the bundles in the leaf as its development
proceeds, and (2) on the arrangement of the bundles in the stock.
in the older plant.
It is an obvious fact, which may be observed on comparing
plants of different ages, that the plumular leaves increase in
width as they grow older, and that this is accompanied by an
increase in the number of their vascular bundles. The question
therefore arises—How and where the fresh bundles are formed ?
The course of the first two bundles of the plumular leaf was
described in my former paper (cf. fig. 15, 4). Comparing this
with our fig. vir, we see that at first, at all events, the number
of bundles is increased by the successive development of fresh
bundles near to the margins of the leaves. In the case in question
we have two pairs of such secondary bundles, but this mode of
increase in number of the bundles is not continued in the later
stages of development ; this is proved by such an appearance as
that presented in fig. vi, 6, 7. On carefully examining such
sections as the former of these no trace of young marginal bundles
in course of development is to be found. On the other hand,
there appear between the older bundles of the leaf trace younger
bundles, as shown in fig. v1, 7, which are evidently freshly inter-
calated between the pre-existing bundles of the leaf trace. In
fig. x11 we have further evidence of this intercalation of fresh
bundles, which seems to be more common in older than in
younger plants. These younger intercalated bundles run parallel
to the older series, but do not extend so far into the stem; in
fact, those bundles which are youngest follow the plane of the leaf
for the shortest distance into the stem. We have, then, an
explanation afforded us of the difference of the bundles in this
respect, and we may presume that the same rule applies to the
bundles of the leaf trace throughout, that is, that the oldest
bundles are those which extend furthest into the stem in the
plane of the leaf, while those which extend successively a less
distance are younger. And this leads us to the second point,
viz. the bearing of these conclusions upon the arrangement of the.
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS. 587
bundles in the lower part of the stock. It has been described
by Hooker (p. 14) how in the stock and root of old plants the
peripheral bundles are arranged in rings. The outermost of
these rings is the youngest. This is the natural result of a
process of continued intercalation of fresh bundles of the leaf
trace as above described, followed in each case by a curvature of
the newly-formed bundle out of the plane of the leaf trace into
the peripheral part of the stem: and since before this curvature
each new bundle proceeds a shorter distance towards the centre
of the stem than the next older bundles, it will appear in trans-
verse section of the stem nearer the circumference of the section
than they. A similar explanation of the arrangement of bundles
may be given for the crown; here, however, the bundles are less
regularly arranged.
Immediately below the surface of the lips of the leaf groove
is to be seen a very complicated network of anastomosing
bundles, usually of small size. These are represented in fig. x1,
which includes the lower lip of the groove. I did not observe
any blind endings of these bundles, though such endings may
exist. Still to prove this is very difficult, since the bundles
pursue a most tortuous course. A similar system of bundles is
found at the periphery of the crown. ‘These bundles are accom-
panied by tracheids with reticulated walls (v’ Mohl’s “ transfu-
sions Gewebe ;” ef. Strasburger, ‘Coniferen,’ p. 99). In old plants
these bundles attain a considerable size, so that they can easily
be recognised with the naked eye. Further from the lip, most of
these bundles join some few main trunks, which pursue a more
regular course, and finally join the descending bundles of the
leaf trace. But all of them do not end thus. As before men-
tioned the corky degradation of tissue at the apex of the
plant often includes vascular bundies, and this is especially
common in older plants. It is certain of these ramifying bundles
which are thus included in the degraded tissue.
We have seen in my former paper that in the earlier stages of
development the vascular system of Welwitschia does not differ
greatly from that of other allied plants. The primary structure
of the root corresponds closely to that of Hphedra, while the
arrangement of the bundles of the hypocotyledonary stem presents
no very remarkable peculiarities, It is only when the plumular
leaves begin to develop that the vascular system assumes an
arrangement peculiar to this plant. Still it is interesting to
trace, even in plants of considerable age, how close is the corre-
spondence in arrangement of bundles to that described in my
former paper on the seedling of the plant.
In the root the secondary thickening proceeds at first in the
normal manner, and though, as the age increases, fresh peripheral
588 F. O. BOWER.
bundles are formed, still even in very old roots the primary xylem
masses and the first products of secondary thickening may be
observed with certainty.
Passing upwards from the root to the hypocotyledonary stem,
we have seen that in a plant of considerable age (fig. m1) the
course of the primary xylem groups could be accurately followed ;
that as we pass from the root upwards the two primary xylem
groups separate; that each divides into distinct parts ; that these
four parts could be traced into the hypocotyledonary stem, in a
transyerse section of which there appears round each of the
four primary xylem groups a number of secondary bundles
arranged in a radiate manner. Comparing these facts with the
observations recorded in my former paper on the seedling, it will
be seen that the lower part of the plant retains for a considerable
time an arrangement of the vascular tissues which is very closely
related to that of the seedling. This grouping of the secondary
vascnlar bundles round four centres corresponding to the original
vascular bundles of the seedling may also be observed in plants
of much greater age than thai represented in fig. ur. Sir Joseph
Hooker observed and figured it, though, as the structure of the
seedling was then unknown, the explanation of the fact was not
obvious.
As we approach the plumular leaves the arrangement of the
secondary vascular bundles corresponds less closely to that of the
primary bundles of the seedling, and seems to be determined
rather by the form and position of the plumular leaves than by
relation to the pre-existmg bundles. The vascular arrangement
at the upper part of the plant having been fully described above
need not be here recapitulated ; we must, however, for a moment
notice the system of small frequently anastomosing bundles
which is found immediately below the surfaces of the leaf groove.
Those are, as far as I know, unique. They do not extend far,
and appear as a rule to be thrown off with the masses of effete
tissue which cover the apical part of the stock and crown. They
appear, therefore, to be in the main a temporary system. It is
with them that the vascular system of the fertile branches is con-
nected, as will be stated below.
Comparisons have been drawn between the bundle system of
Welwitschia and that of other plants. For instance, Strasburger
(* Conif. ti. Gnet.,’ p. 376) compares the stem with that of the
Piperacee, Amaranthacee, and Nyctaginee, while De Bary
(‘ Vergl. Anat.,’ p. 634) cites, in connection with it, the Cheno-
podiaceze, Amarantacez, and Mirabilis, There are undoubtedly
points in common between these and Welwitschia. It still
remains, however, to investigate the structure of various plantg
cited by Hooker and Strasburger as having an external confor.
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 589
mation more or less like that of Welwitschia, and it is perhaps
in these plants that we may hope to find the closest similarity of
vascular arrangement to that in Welwitschia, which appears at
present unique, and more especially so at the upper part of the
plant.
Development of Fertile Branches.
The origin of the fertile branches is a point hitherto unobserved.
I have been supplied from the Kew collections with material for
the study of the development of the male branches. Since the
position, appearance, and structure of the female branches is
similar to these in the mature state, we may, for the present,
assume that they resemble them also in their mode of develop-
ment.
The development begins at some distance from the base of the
leaf groove, and usually on the inner lip of the groove, though
exceptions to this rule are cited by Hooker (p. 20). The point
at which the development of a fertile branch is about to begin
may be recognised externally as a dark dot, the change of
colour of the tissues at that point being due to the increase in
the quantity of starch and protoplasm which they contain.
First there appears a ring-like depression of the surface (fig.
x11, 1); this depression deepens, while the central part enclosed
by it grows on (2). As the development proceeds, that part
of the ring furthest from the base of the leaf groove is more
depressed than the part nearer to it. The result of this is that
the central cone, which assumes the functions of the apical cone
of the young branch, is turned upward (3, 4). The apex
of the cone does not rise above the level of the surface of
the lip, and it is thus protected during its early stages from
pressure of the plumular leaf. The tissues surrounding the
depression grow meanwhile more rapidly, so that the apex of the
young branch is gradually arched over by flaps of irregular shape,
which give to the branch, when seen from above (fig. x11, 5), an
appearance as though it had been developed endogenously, and
were breaking through the external tissues. This appear-
ance remains after the branch has finally developed, the base of
it being surrounded by an irregular margin (fig. xtv). Leaves
are produced laterally on the apical cone of the young branch;
these appear in successive decussating pairs, the first pair being
anterior and posterior. The process of extension I have not been
able to trace, but there is no doubt that it begins below the
lowest pair of leaves, since (1) no traces of leaves are to be
found at the base of the mature fertile branch, (2) the lowest
pair of leaves of the mature branch are in the same position
relatively to the plant as the first pair developed on the young
590 . F. 0. BOWER.
fertile branch, 7.¢e. anterior and posterior. As to the further
external characters of the fertile branches I need only refer to
writings of Hooker, Strasburger, and MacNab. I have nothing
to add to the detailed account given by Strasburger (‘ Coniferen,’
pp. 141, &c.) of the structure of the fertile branches. As he
describes, the bundles run nearly parallel down them. As they
enter the main stem of the plant they anastomose with one
another, and passing inwards, are almost immediately lost in the
anastomising network of bundles already described beneath the
surface of the lip. With these bundles they appear to fuse
(fig. xv).
‘We thus see that the origin of the male branches is exogenous,
and since they first appear on the lip of the groove at some
distance above its base they are adventitious.
Development of Spicular Celis.
As before stated, it appears that any cell of the active paren-
chyma may develop into a spicular cell. It is, however, at the
lower part of the leaf that the first stages of this process are
most easily followed, since there the tissues are in a state of
rapid differentiation from a mass of uniform tissue, such as that
seen in fig. x. In the mesophyll, which is still actively dividing,
certain cells cease to divide, increase in size, and put out protru-
sious in two or more directions. These grow apparently at their
apex, and push their way between the other tissues at the
angles where the cells meet (fig. xv). ‘These cells remain singly
nucleated, and I have never observed a spicular cell with more
than one nucleus. In spicular cells developing in the stock or
crown, the growing ends seek out and follow the intercellular
spaces, where growth is naturally easiest (fig. xvi). As the
cell increases in size the cell wall becomes differentiated into an
outer cellulose wall and an inner lignified wall. The well-known
crystals of calcium oxalate assume, at a very early stage, their
final development, as may be seen in figs. xvii—xx. They
are so placed as to remain with one side in contact with the
cellulose wall, while the other sides are contiguous with the inner
lignified wall (fig. x1x). That the outer cellulose wall is not
merely composed of the cellulose walls of the surrounding cells
(as might be concluded from such a case as that in fig. xx) is
shown by the existence of it in those parts of the wall of spicular
cells which abut on intercellular spaces (fig. xvit). The cellu-
losew all remains permanent. As the cell develops the lignified
inner wall increases in thickness, till in the fully-formed spicular
cell the cavity is almost obliterated (fig. xx). This inner ligni-
fied wall is not uniform. In both longitudinal and transverse
sections pits are to be seen scattered irregularly between the
i
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS. 591
crystals; these are represented in fig. xviit as dark dots. They
extend from the outer cellulose wall to the cell cavity, and are
filled with plugs of protoplasm (fig. xtx), which are continuous
as far as the outer cellulose wall. The protoplasmic contents
become more and more reduced as the development of the ligni-
fied walls proceeds, till they appear to be finally lost.
The mode of development of the spicular cells may be com-
pared with that of the internal hairs in the intercellular spaces
of the Nymphzeacez, and in the tissues of certain Aroidee (cf.
De Bary, ‘ Vergl. Anat.,’ p. 230, &c., where the literature is
cited). The spicular cells are an interesting intermediate between
these and sclerenchyma fibres, which they resemble in many
respects.
Sieve Tubes.
The sieve tubes of Welwitschia have already been described
by Strasburger (‘Coniferen,’ p. 380), and figured by Bertrand
(“Cellules grillagées,” ‘Ann. d. Sci. Nat.,’ série v, vol. xx).
But in longitudinal sections from the root I have obtained differ-
ent results from the latter writer. I find the sieve tubes to
resemble those of the other Gymnosperms in their general cha-
racters, but the sieve plates are collected almost exclusively on
their sloping ends (fig. xxt). Occasionally one is met with on
the lateral walls. The sieve plates are often coloured a sherry-
brown with Schultz solution, while the rest of the walls is blue.
The contents are transparent and almost free from granules.
Between the sieve tubes appear cells of the bast parenchyma.
Results.
1. The cotyledons wither and fall off, and the pair of leaves of
the mature plant are the first pair of plumular leaves.
2. The crown is derived entirely from the continued growth
of two lobes (axillary buds), which appear in the axils of the
cotyledons. ‘The apical cone of the plant remains rudimentary.
3. The parenchymatous “ground tissue” throughout the
plant remains, for a long period at least, capable of active growth
nd division (halbmeristematisch). The results of this are (a)
increase in bulk of the tissue itself; (4) production of fresh
spicular cells, and sclerenchyma fibres by the growth of single
cells of it; (¢) formation of fresh vascular bundles by means
of repeated divisions at certain points.
N.B.—It should here be observed that the active tissue has a
different origin in different parts of the plant; in the root it is
derived from the “tissu conjunctif” of Van Tieghem, in the
stem from the fundamental tissue generally.
592 F, 0. BOWER.
4. The directions of cell division at the base of the leaf groove
are such as to bring about— .
(a) Increase in length of the leaf.
(4) Increase in length of the whole plant.
(c) Increase of the tissues in a direction perpendicular to the
surface of the groove, and hence increase in bulk of the crown
on the one hand, and of the stock on the other.
5. The two originally separate primary xylem masses of the
root unite centrally at a short distance below the feeder, so as to
form a single plate. Above the point of union a parenchymatous
pith remains permanently between them.
6. Further development proceeds in a direction at right
angles to this plate, by means of a cambium layer. The result
is the formation of two masses of secondary vascular tissue sepa-
rated laterally from one another by two broad medullary rays.
Thus far the structure corresponds to that described for Ephedra
(cf. Van Tieghem, La Racine, p. 211).
7. Smaller vascular bundles separate laterally from these
masses of secondary vascular tissue, and pursue a sinuous course
along the medullary rays, fusing from time to time (a) laterally
with the system from which they were derived, and (4) with the
later developed system of peripheral bundles. These bundles
may be compared with the intercalary bundles of many dicoty-
ledonous stems (Zwischenstringe, De Bary, ‘ Vergl. Anat.,’
p- 468).
8. Peripheral bundles appear later; their terminations I
have not been able to trace. They are formed by the specially
localised activity of division in the parenchymatous “ ground
tissue,” and are arranged in more or less regular rings.
9. All bundles of the root remain for a considerable time
open bundles, and by the activity of their cambium may attain a
large size. This is especially the case in the central group.
10. In the arrangement of the vascular bundles of the older
plant at the point of transition from root to stem, there may be
traced a very close relationship to the arrangement at the same
point in the seedling. The differences are due to (1) increase in
size and number of vascular bundles, the later formed bundles
being, however, mainly grouped around the original bundles;
(2) to increase in bulk of the “ ground tissue,” and consequent
increase in absolute distance of the original bundles one from
another.
11. As they pass up the stock the bundles retain for a time
an arrangement obviously related to that in the seedling, but as
the apex is approached this is gradually lost sight of by the
breaking up of the groups of secondary bundles which lower
down surround the primary bundles,
FURTHER DEVELOPMENT OF WELWITSCHIA MIRABILIS, 593
12. The vascular system at the apex of the plant is so arranged
as to keep up the following direct vascular connections :
(a) Between the leaf, and both peripheral and central parts of
the stem.
(4) Between leaf and crown.
(c) Between stock and crown (cauline bundles).
No fundamental change takes place in these relations as the
plant develops.
13. Increase in number of bundles at the base of the leaf is
effected at first while the leaves are young by the development
of fresh bundles at the margin of the leaves, but later by inter-
calation of new young bundles between the older ones, and the
successive peripheral rings of bundles in the stock correspond to
the successive series of bundles thus intercalated.
14, The development of the fertile branches is adventitious
and exogenous. ‘Their vascular system is directly connected
with the network of bundles which ramify below the surface of
the leaf groove. There is no direct connection between the suc-
cessive series of fertile branches and the successive rings of peri-
pheral bundles of the stock, though both probably owe their
serial development to the same causes, 7.¢. alternating periods of
activity and dormancy of the plant.
15. Spicular cells are developed from single cells of the
parenchyma. These undergo apical growth, pushing their way
between the surrounding tissues. They often follow the inter-
cellular spaces. ‘Their walls are differentiated into an outer
cellulose layer and an inner later developed lignified layer. The
crystals of calcium oxalate lie between the two. The lignified
wall is pitted. The cells remain uninuclear.
16. The sieve tubes have their sieve plates collected on their
sloping ends ; here and there a sieve plate is found on their sides.
Postscript.—Since the above paper was written there has
appeared in ‘ The Gardener’s Chronicle,’ August 13th, 1881, an
account by M. Naudin of fresh observations on young plants of
Welwitschia mirabilis, which seem to show that the type of
development, which is constant in the specimens which I have
had the opportunity of observing, is not the only one for this
remarkable plant. In all my specimens the series of members,
as above described, has been—(1) two cotyledons present in the
mature embryo, (2) two plumular leaves decussating with these,
and capable apparently of indefinite growth, (3) two structures
which appear between these, and which, for reasons given above,
I regard as buds in the axils of the cotyledons, (4) apical cone of
the whole plant, which does not develop further. I gather
from M. Naudin’s description that there may be another and
594 F. 0, BOWER.
different type of development, which, moreover, he seems to find
constant. In this case the following succession of members is
found by him—(1) two cotyledons, (2) two small plumular leaves
decussating with the above, (3) a stem about two lines long,
bearing (a) an almost imperceptible Jracteole, (4) a true leaf,
(c) two further leaves, “alternate but very close together, so that
they appear opposite, and which seem to terminate the tigellum.”
I do not doubt that this description points to a further deve-
lopment of the plumule than any which has occurred in the
plants at Kew. In these the axis remained in all cases very
short, and certainly did not attain a length at all approaching
two lines, which is the length stated by M. Naudin for his
lant.
I conclude, then, that the observations of M. Naudin do not
affect the above interpretation of my observations on the plants
at Kew, but rather point to the conclusion that the type of
development which I have described is not universal.
Further, I think it is unlikely that the Kew plants will enter on
the further stage of plumular development as deseribed by
M. Naudin. The oldest seedlings now living at Kew were sown
in August, 1880 (i.e. five or six months before those of M.
Naudin). These, when last I saw them (July, 1881), showed
no outward signs of any deviation from the type which I have
described as normal. Their two plumular leaves were of healthy
appearance, and had attained a size almost equal to that of the
cotyledons. This condition may be contrasted with that de-
scribed by M. Naudin. He expressly mentions that the pair
of leaves succeeding the cotyledons are “ very smad/,” and speaks
of their “‘ growth being apparently arrested.” May we not have to
deal with two alternative types of development—(1) one in which
the first pair of plumular leaves are large, while further develop-
ment of the main axis is arrested; (2) one where the first pair of
plumular leaves are small, while the main axis grows in length
and forms further appendicular members ?
Lastly, M. Naudin suggests the possibility of the two members,
which have been hitherto regarded as leaves, being really flattened
branches. In connection with this I can only say that if (as the
specimens I have examined lead me to believe is the case) the
two leaf-like members of the mature plant are xormally derived
from the first pair of plumular structures, as described in my
first paper, there can be little doubt of their foliar nature. The
only alternative would be the assumption that they are extra-
axillary, z.e. adventitious axes, developed nearer to the apex
than the youngest leaves, a supposition which is warranted
neither by their structure, appearance, or origin.
August 29th, 1881.
ABERRANT FORMS OF LAMELLIBRANCHIATE GILLS, 595
On the StructURE and SIGNIFICANCE of some ABERRANT
Forms of LAMELLIBRANCHIATE Giuts. By K. Mrrsv-
KuRI, Ph. B., of Tokio, Japan, late Fellow of the Johns
Hopkins University, Baltimore. (With Plate XXXIV.)
Tue following contribution to the morphology of the
Molluscan branchie is part of an investigation on which
I have for some time past been engaged, under the direction
of Dr. W. K. Brooks, in Professor Martin’s laboratory at
the Johns Hopkins University. The gills, of which the
description is here given, are those of Nucula proxima and
Yoldia limatula. They are extremely interesting because
of their simple structure, and this account of their minute
structure is published with the hope that it may throw
some additional light on the nature of Lamellibranchiate
gills. I wish to express here my sincere thanks to Dr.
Brooks for his constant advice and assistance. I am also
deeply indebted for specimens used in the investigation to
Professors A. E. Verrill and 8. J. Smith, of Yale College,
and to Mr. Richard Rathbone, of the United States Fish
Commission.
Nucula proxima, Say.
This Lamellibranch shows many departures from the
structure which is generally regarded as characteristic of
the class. Fig. 1 gives a fair idea of what is seen when the
left valve of the shell has been taken away, and the mantle
of the same side removed along the lower border of the
visceral mass near the line vy. a.a. is the anterior abduc-
tor muscle made up of several fasciculi; p. a. is the posterior
abductor. It will be noticed that Nucula possesses one of
the few shells in which the umbo is turned toward the
posterior end. In the specimen figured, the visceral mass
(v. m.) shows convolutions on the surface, which, under the
microscope, proved to be the male reproductive organ, pro-
bably enormously developed for the breeding season, and
this character enables one to distinguish the sex of a speci-
men without difficulty. All the males have these convolu-
tions, and, when preserved in alcohol, are of a greyish colour.
The females show hardly any convolutions, and are much more
darkly coloured. The foot (f) is folded longitudinally at
its end, and can accordingly be spread out into a flat circu-
lar disc. The labial palpi (/) are unusually developed, and
-might at first sight be taken for gills. The inside of the
596 Ke MITSUKURi.
outer and the outside of the inner palpus are raised into
numerous parallel ridges, which, as shown in the figure,
can be seen from the outside, and do not extend to the
lower margin. At their posterior end there are two remark-
able structures. One of them is a hood-like structure
(7. b., figs. 1 and 2), which is the posterior prolongation of
the united upper edges of the inner and outer palpi. The
other (J. a., figs. 1 and 2), lying immediately below the first,
is a long tentacular appendage. It is a hollow tube, open,
however, along a line on its posterior aspect, and having its
cavity continuous with the space between the two palpi.
As it has been seen protruded, with the foot outside of the
shell (Woodward’s ‘Manual of Mollusca,’ p. 426), and
since, in alcoholic specimens, a great deal of dirt and sand
is found along its length and between the palpi from its
base to the mouth, it is no doubt a food-procuring organ,
probably sending a constant stream of nutritive matters to
the mouth by means of its cilia. It is interesting to notice
in connection with this appendage that in Nucuwla, the gills,
unlike those of ordinary Lamellibranchs, must be practically
useless for obtaining food, as will be evident from the fol-
lowing descripion of them. a gn
The gill (g., figs. 1 and 3) is comparatively small. It is
situated quite posteriorly, and is suspended by a membrane
(m., figs. 1 and 3), which is attached to the body along the
broken line zyzw. It is united to the visceral mass (v. m.)
from z to y, and to the upper part of the foot (/, fig. 3) from
y to z (see figs. land 3). At the last point, having come
to the median line of the body, it joins with its fellow of the
opposite side, and they continue in this way as far as w}
Here they separate again, each proceeding to the posterior
tip (p) of the gill of its own side. It should be remarked
that, as the point w is further from the median line of the
body than the point y (fig. 3), there is a considerable free
space beneath the suspending membrane of the gill.
When we turn to the gill itself, we find an altogether
unusual structure. Fig. 4 shows it dissected out and seen
from below and slightly from one side. In general appear-
ance it resembles a boat which is suspended by its keel.
zecp, fig. 4 (seen in cross section at 7), fig. 5), is the line
of attachment and corresponds to the keel; zdyp, fig. 4
(seen in cross-section at d, fig. 5), represents the bottom
line of the hollow of the boat. ‘The latter is bounded by
the two surfaces zapd and cbpd (fig. 4; seen in cross-
section at bd and ad, fig. 5). The anterior end (2, fig. 4)
is rather blunt, while the posterior end (9, figs. 1, 3, and 4)
ABERRANT FORMS OF LAMELLIBRANCHIATE GILLS. 597
is quite pointed. The resemblance of the gill to a boat is,
however, only very superficial, as the gill is not one solid
mass, but is made up of a series of paired plates of a peculiar
shape, placed one after another from the anterior to the pos-
terior end. A little dissection under a lens will show that
the part above the line zdp (fig. 4) and below the line of
suspension (xcp), is continuous along the entire length of
the gill, and that, with this part for the stem, the plates are
given off, one after another, in pairs to the two sides (see
fig. 5). The plates constitute the proper respiratory parts of
the organ. They are largest in the middle, and diminish
in size toward the two extremities.
It is evident from this description that the gill in Nucula
is of quite an exceptional nature. It does not, as in most
Lamellibranchs, extend along the whole length of the side
of the body, constituting the most conspicuous object of the
mantle cavity, but is comparatively insignificant, being
pushed back and freely suspended in the mantle cavity. It
cannot, therefore, divide the latter into the suprabranchial
and infrabranchial chambers, and is, of course, utterly de-
void of any structure like the ciliated water-passages in the
ordinary gill, for driving water from the lower to the upper.
It cannot, also, as has been said, serve as an effective food-
procuring organ. ‘The gill in Nwcula must for these reasons
be of vastly less functional importance to the animal than it
is in common Lamellibranchs, and, so far as I am able to
see, serves only as the organ of respiration. It seems to me,
however, that the division of the mantle cavity into the
upper and lower chambers is begun in the posterior part.
It has been seen that ventral to the membrane suspending
the gill (m, figs. 1 and 3) there is a large space continuons
with the general branchial cavity, and there certainly is
a space dorsal to this membrane. These spaces seem to be
the rudiments of the supra- and infrabranchial chambers.
Moreover, the arrangement of the different parts at the
posterior end, as seen in fig. 3, recalls that of the correspond-
ing parts in many of those genera in which the mantle cavity
is divided into two parts. It is not difficult to conceive how
the same division might be brought about in the case of
Nucula, by proper development of the gill and the mem-
brane.
Fig. 5 shows a pair of opposed plates considerably en-
larged. The solid part (¢ dj) which I have called the stem,
and which is continuous throughout the whole length of the
gill, together with the suspending membrane (4 77 /) is seen
in cross section in the middle, and from this middle portion
VOL, XXI.—-NEW SER. RR
598 K. MITSUKURI.
the paired plates (e. ¢,) are seen to proceed. The coloured
part at the bottom represents the complex chitinous frame-
work. The membrane (4 77 /) is made up of fibrous
tissue, the bundles of which this is composed crossing each
other in many directions. Its free surfaces are covered
with columnar epithelium. The stem consists mostly of a
solid mass of large irregular cells with rather large nuclei.
There are, I am almost certain, ¢wo blood-channels exca-
vated through it; a lower larger (7), and an upper smaller
(0). The latter seems to be in connection with a free space
(g.) found often in sections of the suspending membrane.
The large channel (z) sends a branch (r) into each plate.
The fibrous tissue found in the upper membrane dips down
into this part at regular intervals, viz. between every branch
(r) of the lower blood channel (x). How these fibres end
below, when they reach the chitinous framework, I have
not been able to make out. A few fibres (w) are sent down
into the plate a little above the blood-channel (7), and
gradually approach and finally touch the latter near its
lower end. A few more fibres (¢) are seen along the upper
edge of the plate. Exactly what this fibrous tissue is 1 am
unable to make out, but it seems to be some sort of tough
connective tissue, with perhaps muscular fibres more or less
intermixed. ‘That it is very tough and serves as a support
to the whole structure is seen by the fact that the fibres
often stick out beyond the broken edge of the soft tissues.
The trough of the chitinous framework is seen at s,in
cross-section. It extends along the whole length of the gill
and sends out two branches into each plate. I have ob-
tained the appearances, in some sections, of a bundle of
fibrous tissue running in it and filling it. The framework
will be described more fully further on. The plates (e), the
proper respiratory organs, are comparatively speaking very
broad and quite thin, and hang down from the solid part of
the gill. The epithelium of the plates which is repre-
sented in the figure as ending abruptly at the edges ¢ d and
Jj d, turns at a right angle at these lines to cover the stem,
and is soon reflected outwards again to form the epithelium
of the next plate in the series. This is evident from an
inspection of fig. 8. Hach plate may be said to be simply
an enormously widened blood-channel (fig. 6), and as the
blcod is necessarily spread out in a thin layer over a large
area, the purposes of aération must be admirably served.
The columnar epithelial cells seen at ad, fig. 5, are very
characteristic of the plates under a microscope, and are the
cells (dq, fig. 6) around the chitinous bars (A, figs. 9 and 6)
ae
-
ABERRANT FORMS OF LAMELLIBRANCHIATE GILLS, 599
seen in optical section. The surface of the irregularly rect-
angular cells placed just inside these columnar cells in fig.
5, ought therefore to be continuous with the outer edge of
the columnar cells, but in order to avoid confusion is not so
represented in the figure. - This is also the case with the
cubical cells along the upper edge. The chitinous support
(A, figs. 5 and 6) of the plate runs near the lower edge (fig.
5) to its tip (a or 4, fig. 5), and is made up of two entirely
separate parts (seen in cross-section in fig. 6) applied closely
together. Owing to the shape of these parts there is, how-
ever, a narrow oval space between them. ‘This space, as
will be shown further on, is continuous with the space in the
trough (s, fig. 5) of the stem. ‘The cells along the lower
edge of the plate are columnar, and surround the chitinous
support in a characteristic manner shown in fig. 6. Their
surface outlines are irregularly rectangular, contrasting
with the irregularly polygonal cells covering the rest of the
plate. The branch (r, figs. 5 and 6) of the lower blood-
channel (7) in the s¢em, is seen to be circular in cross-section
and to bulge out the surface of the plate. These points are
not, however, constant, as the vessel is sometimes constricted
into more or less separate channels, while the amount of
bulging seems to depend on the quantity of blood present.
The remaining part of the plate (e, figs. 5 and 6) is flat and
quite thin, enclosing a broad blood-channel between its two
epithelial surfaces. It is here no doubt that the aération of
blood is accomplished. ‘The cells of this part are cubical, as
seen in fig. 6. Some of them send processes inward to join
others from the opposite side. This gives a labyrinthine
appearance to this part of the plate. The course of the
blood is evidently from one blood-channel in the stem to the
~other, through the space in the plate. For instance, the
blood may start from the upper channel (0) in the stem, go
to the broad flat part (e, fig. 5) of the plate where it gets
aérated, then enter the branch (7), along its upper edge, and
run up this to reach the lower blood-channel (v e) in the stem.
This is, however, a purely hypothetical course. I have had
no means of determining whether the blood goes from the
upper to the lower channel or vice versd.
The framework which supports the gill can be separated
out by heating it in dilute caustic potash, as it is insoluble
in weak acids and alkalies. It is stained by carmine and
other colouring reagents. Whether it is really formed of
chitin Ido not know, but as previous writers have described
the substance as of that nature it will be convenient to use
the term ‘‘ chitinous support” for the present. The frame-
600 K, MITSUKURI.
work consists of a trough (seen in cross-section at s, fig. 5;
longitudinally from below in fig. 8; diagramatically repre-
sented in fig. 7), which runs along the whole length of the
gill, and from which a pair of closely-applied parallel
branches (A, figs. 5, 6, 7, and 8) is given off into each plate.
The trough is divided into two unequal parts: an upper
larger and a lower smaller, by a cross piece (c. p., figs. 5
and 7), which stretches from one side of it to the other, a
little below the middle. This cross piece is not, however,
continuous, but is pierced through by oral openings (0 2, figs.
7 and 8) whenever branches are given off laterally to the
plates. The space enclosed between each pair of closely-
applied branches (see A, figs. 6, 7, and 8) is connected with
the lower compartment of the trough by means of somewhat
circular openings (0p, and o’ py’, figs. 7 and 8) found near
the bottom. In fig. 8 the letters a,a,a,are placed opposite
each pair of the branches that go intoa plate. It will be
seen how one half of the chitinous support of one plate, after
forming an arch at the trough, turns round to enter the
next plate in succession, and to constitute there one half of
the support of that plate. The framewerk treated with pot-
ash, and sometimes without any treatment, shows marked
longitudinal striation (fig. 8), and some of its fibres stick-
ing out at the broken edge beyond the others resemble in
appearance the fibres found in the suspending membrane,
at ¢and uw, fig. 5, and give reasons for thinking that the
whole chitinous framework is nothing but the fibrous tissue
found in other parts cemented closely together and forming
one cohering mass.
Although, owing to the state of the specimens, I have
obtained only here and there evidences of cilia, it seems
reasonable to suppose that the whole gill is covered with
cilia. On two rows of cells (0. f., fig. 6; d. a., fig. 5) on the
lower edge of the plate I believe there are larger cilia than
on the rest, as I have now and then seen their remains, and
as, without any question, cells in the corresponding posi-
tions in Yoldia have long and conspicuous cilia.
Yoldia limatula, Say.
Yoldia resembles Nucula in several structural peculiari-
ties—in its well-developed labial palpi, with their peculiar
food-procuring appendage, in its feather-like gills, in the pos-
terior position and comparatively small size of the gills, and
the consequent absence of the division of the mantle cavity
into the supra and infrabranchial chambers. It differs from
ABERRANT FORMS OF LAMELLIBRANCHIATE GILLS, 601
Nucula in having a siphon, and further shows its departure
from the ordinary lamellibranchiate structure in having a
highly specialised tactile organ in the siphon.’
The gill, although different in details from that of Nucula,
is essentially of the same structure as the latter. It is sus-
pended by a membrane, as in Nucula. Fig. 9 shows it dis-
sected out by itself. The line of suspension is cep; «dp
is the ventral median line, and corresponds to zdp in fig.
4. As in Nucula, the gill is made up of a series of paired
plates, placed one after another, and attached to the central
solid stem continuous throughout the whole length of the
gill. The plates do not, however, project downward, as we
have seen in the case of Nucula, but here turn upward (see
fig. 11). The plates are largest in the middle, and gradually
become smaller toward the extremities. At the front end
(z, fig. 9) there is a rather interesting arrangement. Fig.
10 shows diagrammatically the relations of the various parts
at the anterior termination of the gill. It will be seen that
the plates of the gill gradually become smaller and finally
die out toward the front, and the gill is continued simply as
a flat membranous structure (z, fig. 10), which goes into
the visceral mass (v. m., figs. 9 and 10). A cross-section of
this part shows that at its lower portion, at least, there is a
blood-channel, probably continuous with one of the channels
in the stem of the gill. In some specimens this membrane-
like portion of the branchia is longer than in others, and
goes some distance around the visceral mass.
Owing to the rather poor state of preservation of the
alcoholic specimens, I have not been able to make out the
histology of the Yoldia gill as fully as I should like, but the
following description I believe to be correct in essential
points :—Fig. 11 represent an opposed pair of plates, and cor-
responds to fig. 5 of the Nuweula branchia. The suspending
membrane (47277) consists of fibres crossing each other in
several directions, and is covered on its two surfaces by
columnar epithelium. The solid stem (tidy) of the gill has
two blood-channels, an upper (”) and a lower (0). The
latter seems to be in communication with a comparatively
free space (q) in the middle of the suspending membrane.
Directly below the upper blood-channel (0) there is a bundle
of tissue, which appears to be fibrous, running the length
of the gill (seen in cross-section at f, fig. 11). It serves no
doubt for support. The floor of the lower blood-channel (7)
is covered by a V-shaped bundle of longitudinal fibres (s).
1 W. K. Brooks, ‘Proc. Amer, Ass, Adv, Sci.,’ 1874 (end of note),
602 K. MITSUKURI.
This would seem to be homologous with the trough-shaped
chitinous structure in Nucula, but seems to be formed of the
same fibres already referred to several times, which are
found in the suspending membrane and other parts of the
Nucula and Yoldia gills, and I cannot establish any con-
nection between this bundle and the chitinous bars (Ah, fig.
11) in each plate. The latter, when they reach the longi-
tudinal bundle (s), make a bend and turn out again to enter
the next plate in the series. In some sections I have ob-
tained indications of a very thin layer of chitin beneath
the fibrous bundle (s), which may, therefore, correspond to
the fibres found 7 the trough of the framework in the
Nucula gill (see above). If, however, this Y-shaped struc-
ture is really homologous with the trough of the Nucula
gill, it goes far in support of the view advanced above, that
the chitinous framework is really made up of the fibrous
tissue which is found in other parts, here cemented into
one compact mass. In such a case fusion has gone further
in Nucula than in Yoldia, and we see in the first genus the
trough well united with the branches () in each plate.
The plates (e, fig. 11) in Yoldia spread themselves upward
instead of downward, as in Nucula. The chitinous bars
(i), of which there are two in each plate, follow the curve
of the plate and end rather bluntly about half way up, at
the point @. ‘That the part from d to a@ corresponds to the
lower inner edge of the Nucula plate (da, fig. 5) is shown
by the characteristic rows of columnar cells having longer
cilia than those found in other parts of the gill. There is
another system of chitinous strnctures (ch, fig. 11). Many
fine chitinous filaments come down together in a bundle on
each side from the suspending membrane, and as soon as
each bundle reaches the plate of its own side filaments
spread themselves out like the frame of a fan over the whole
plate. Several fibres sometimes proceed together, and then
separating give the appearance of branching. They are
found directly beneath the epithelial cells that cover the
plate. The effect of this framework must be to keep the
plate well spread out for the purpose of aération. I have
not succeeded in obtaining any single section which shows
the structure of the plate well, but from the comparison of a
good many sections which I have made, I feel tolerably sure
that the whole space between the epithelial surfaces is per-
vaded by what Peck! calls “lacunar tissue” (fig. 12). Itis
1 R. Holman Peck, “The Minute Structure of the Gills of Lamelli-
branch Mollusea,”’ ‘ Quart. Journ. Micros, Sci.,’? 1877.
ABERRANT FORMS OF LAMELLIBKRANCHIATE GILLS, 603
a loose trabecular tissue with many nuclei and within whose
network blood can flow. The space between the chitinous
bars (A, fig. 11), which is quite large in Yoldia, seems to be
tolerably free from this lacunar tissue. Fig. 11 @ gives the
outline of the plate seen from one side.
Theoretical Considerations.
The gills, here described, of Nucula and Yoldia are, 1
think, the most rudimentary of any that have been studied
so far. In fact, at first sight, the resemblance to the ordi-
nary Lamellibranch gill is not apparent, and they suggest
more the Cephalopod gill. But I believe, the homology of
their various parts with those of more complex gills in
Unio, Mytilus, Arca, &c., is not difficult to make out.
After consulting the articles by Peck (loc. cit.), Posner,!
Lacaze-Duthiers,? Bonnet,®? and others, and also after ex-
amining the sections I myself have obtained of Unio,
Modiola, Scapharca, &c., 1 have no doubt whatever that the
plates in Nucula and Yoldia represent the descending or
attached limb of the filaments in the owter and inner gill-
plates in forms like Mytilus, Modiola,and Arca, and accord-
ingly are homologous with the folds on the izmer lamella of
the outer gill-plate, and on the outer lamella of the inner
gill-plate in Unio, Anodon, and Dreissena. If a comparisou
is made of my-fig. 6 with any of the cross-sections of gill-
filaments given by Peck, it will be seen at once how
similarly the paired chitinous bars are placed, how almost
identically the epithelial cells are arranged around them,
how two rows of those cells (/. f,, fig. 6)—called by Peck
latero-frontal epithelial—have longer cilia than the rest.
In fact, Peck’s fig. 12 (a transverse section of a filament of
the Anodon gill) agrees with my fig. 6 in all essential points.
The left hand-figure in his fig. 5 (the superficial view of the
edge of a gill-filament of Mytilus showing the latero-frontal
and other epithelial cells) and the upper’part of his fig. 20
(the same view of a gill-filament of Anodon) would pass very
well for the corresponding part in Nucula. So far as I can
make out from rather poor specimens, the latero-frontal cells
in Nucula are strikingly like those represented in Peek’s
' Carl Posner, “ Ueber den Bau der Najadenkieme,” ‘ Archiv. fiir
mikros. Anat.,’ 1875.
* Henri de Lacaze-Duthiers, “‘ Mémoire sur le Developpement des
Branchies des Mollusques Acephales Lamellibranches,” ‘ Ann, d. Sci. Nat.,’
Ser. iv, tome v, 1856.
3 Robert Bonnet, “Der Bau u. die Circulations-verhiiltnisse der Ace-
phalenkieme,” ‘ Morphologisches,’ Jahrbuch iii, 1879.
604 K. MITSUKURI.
fig. 20. If, then, the plates in the gills of Nucula and
Yoldia represent the gill-filaments in other genera, it
follows from the embryological observations of Lacaze-
Duthiers’ (loc. cit.), and from the position of the chitinous
bars in the plates, that they are homologous with the de-
scending limb of the gill-filaments in ordinary Lamelli-
branchs. Professor Huxley seems to have no doubt what-
ever of the homology stated here, as will appear from the
quotation given further on. Admitting, then, that this sup-
position is correct, and that the gills in Nucula and Yoldia
are in an unusually rudimentary condition, what light, if
any, do they throw on the organogeny of the Lamellibran-
chiate gill? But, before proceeding to the discussion of this
point, let us review briefly what theories have been ad-
vanced as to what is the most primitive type of the bran-
chie of this group. Setting aside older authors like
Williams and Hancock, I consider the articles, already
_ alluded to, by Peck, Posner, and Lacaze-Duthiers as having
the most important bearing on the subject. Posner, after
a careful histological examination of the gills of Anodon,
Unio, Cardium, Mya, Mytilus, Ostrea, Pecten, Pholas,
Pinna, Scrobicularia, Solen, Solecurtus, and Venus, puts
forward, although with hesitation, the theory that the pouch-
like gills of the Unionide are the most primitive type of the
Lamellibranchiate gill. Stepanoff,! so far as I can gather,
inclines to this view. Peck, on the other hand, after an
investigation of Arca, Mytilus, Anodon, and Dreissena,
comes to the conclusion that “the gill-plates of the Unio~
nide are a highly modified form derived from a simple con-
dition in which the gills consist no¢ of plates but of a series
of juxtaposed independent filaments, such as we see in a less
modified state in Arca and Mytilus.” This view is the
more generally accepted of the two. The only complete
history of the development of the Lamellibranchiate gill by
Lacaze-Duthiers (loc. cit.) and all the fragmentary embryo-
logical observations on the organ show that the gills are at
first of a tentacular or filamentary character. Those who
read carefully Mr. Peck’s paper, will, I think, feel con-
vinced by the arguments he brings forward. So high an
authority as Professor Huxley is entirely of this view. He
says :—“In its simplest form, the branchia of a Lamelli-
branch consists of a stem fringed by a double series of fila-
ments (e.g. Nucula). The next degree of complication
arises from these filaments becoming, as it were, doubled
* Paul Stepanoff, ‘ Ueber die Geschlectsorgane und die Entwicklung
von Cyclas,” ‘ Archiy f. Naturgesch,,’ 1865.
ABERRANT FORMS OF LAMELLIBRANCHIATE GILLS. 605
upon themselves at the free ends, the reflected portions
lying on the outer side of the outer, and on the inner side
of the inner, series of filaments . . . (Mytilus Pecten).
In most Lamellibranchs, the gills are four elongated plates,
each of which is in fact a long narrow pouch, with its open
end turned toward the hemal face of the body ” (‘ Inverte-
brates,’ pp. 408-9, Am. Ed.). My own observations lead me
to the same conclusion. In fact, it is difficult to see how
the pouch-like gills of Unzo can give rise to such forms of
branchie as are found in Nucula and Yoldia. By a very
circuitous route they may have degenerated into their
present rudimentary state, it is true, but all recent observa-
tions tend to show that while other organs in the Lamelli-
branchiata have been steadily degenerating, the gills, on the
contrary, have become highly developed and perform func-
tions which the probable change of the animal from the
motile to the sedentary habits of life has forced on these
gills. If, then, there has been no considerable degeneration,
and if the homologies of different parts of these branchiz
are, as I have stated above, the filamentary character of the
primitive Lamellibranchiate gill is placed beyond doubt.
I believe further light is thrown on the subject by the
gills of Nucula and Yoldia. Peck shows that the gills
primarily consisted of a series of filaments, but does not
attempt to account for the fact that these filaments have
come out in long rows on the side of the body. I venture
to suggest an explanation. If we reflect for a moment, I
think we shall see that the gills of Nwcula and Yoldia may
be considered as a stem which, being folded on either side
to increase the surface of contact with the water, gives rise
to the flat plates which I have homologized with the de-
scending limb of the gill-filament of Myti/us and other like
forms. The plates are, strictly speaking, nothing but the
epithelial covering of the stem raised into folds and enclos-
ing between the two sides of the folds a blood-channel. In
the case of Yoldia mesoblastic lacunar tissue is carried out
into the folds. According to this theory, the gill of the
Lamellibranchiata was originally a longitudinal ridge on the
side of the body. Probably in this a blood-vessel ran, and
must have served as the organ of respiration. In course of
time, however, this ridge became folded for the increase of
the surface of contact with the water and thus produced
papilla on its two sides—rudiments of the future gill fila-
ments. The gills of Nucula and Yoldia have gone but
little beyond this stage. I think there is much to support
this view. Stepanoff (loc. cit.) observed in Cyclas that the
606 K. MITSUKURI.
gills arise first as.a ridge on each side of the body. Leydig?
makes the same statement. M. Lovén’s® observations have
a still more important bearing on the point. He says :—
‘* Nous avons, si je ne me trompe, vu la premiére formation
des branchies ; nous en savons assez pour étre sir qu’elles
se montrent sous la forme d’un cordon fin, renflé a certains
intervalles ; que ces renflements se contournent plus tard en
anses, qui s’allongent de plus en plus, et sur lesquelles se
développent les cils vibratiles reguliérement disposés et d’un
forme particuliére.”? “Un cordon fin renflé a certains in-
tervalles” is, it seems to me, nothing but a ridge with slight
swellings or papille. Lovén’s figures are not exactly clear
to me, but what he designates as the gills are certainly in
favour of my view. In all the fragmentary embryological
observations, the gills are generally seen as papill, or
nothing but the folds of a blood-channel. I have already
called attention to the anterior part of the Yoldia gill where
the plates die out and the gill is continued simply as a
ridge containing a blood-channel. Whether this is a rem-
nant of the primitive ridge or not it is difficult to determine,
but the fact that there can be on the side of the body a thin-
walled ridge which, containing a blood-channel, must serve
more or less for respiration, goes far in support of the view
here advanced.
To review the whole matter, the Lamellibranch gill was
perhaps originally a simple ridge on the side of the body,
but to increase the surface of contact with the water folds
may have arisen on two sides of this ridge. If such was
the case, Nucula and Yoldia are still in a stage only very
little advanced from this primitive condition. In course of
time, however, as some of the Lamellibranchiata, either
owing to degeneration or some other cause, become incapable
of extensive locomotion, these buds or folds were perhaps
prolonged to form tentacular filaments, which, going on in
their development, finally produced such complex gill struc-
ture as we see in Mytilus, Unio, Ostrea, and other forms,
taking on at the same time functions totally foreign to their
1 Franz Leydig, “ Ueber Cyclas cornea,” ‘ Miiller’s Archiv,’ 1855. He
says :—“ Die letzte Hauptmandering im dusseren Habitus esfahrt der
Embryo durch die Bildung der Kiemen. Auch sie wachsen als Leisten von
hinten nach vorne und zwar geben sie urspriinglich yon Mantel aus ”
. 62).
Bidnae till Kamedornen om utvecklingen af mollusca acephala
Lamellibranchiata,” ‘Memoirs of the Academy of Stockholm, 1848,
lately reprinted in an abridged form in German. ~
§ Translated by M. Young, and quoted by Lacaze-Duthiers in the article
already referred to.
ABERRANT FORMS OF LAMELLIBRANCHIATE GILLS, 607
original one. Between the simple gills of Nwcula and most
complex ones known, there are a great many intermediate
stages, some going more in one direction, others in another.
For instance, Lucena and Corbis are said to have only one
gill-plate on each side (‘Owen’s Inverteb.’). According to
Sars, Pecchiola is in the same condition (‘ Remarkable
Forms of Animal Life,’ G. O. Sars). Chamostrea and Myo-
chama are described by Hancock (‘ Ann. and Mag. of Nat.
Hist.,’ 1852-3) as having the inner gill-plate complete, but
the outer plate lacking the outer lamella. In these tentacular
filaments seem to be fused with each other. On the other
hand, although Arca, Mytilus, Modiola, have all the lamelle
present, the filaments composing them have not fused with
one another. It is interesting to notice that Nucula and
Yoldia, in which the gills have remained rudimentary,
have, as Dr. Brooks first pointed out to me, an unusual
power of locomotion, while forms wholly or almost wholly
unable to move, as Ostrea, Pholas, &c., possess highly-
developed gills.
For some reason the inner gill-plate seems to develop
further than the outer. For instance, in many genera, the
inner is much larger than the outer. In Chamostrea and
Myochama, already referred to, it is the inner gill-plate that
is complete, and the outer gill-plate that lacks a lamella. It
will also be seen a little further on that in Anodon the inner
gill-plate has gone further than the outer in its development.
In the embryological study of the branchie of Mytilus
Lacaze-Duthiers observed that the filaments of the inner
gill budded out first.
It is very instructive to see the process of secondary fold-
ing going on in higher varieties of the gill. The two
lamelle of a gill-plate are, in such a case, no longer parallel,
but wavy, and the surface of a lamella is thus considerably
increased. In Anodon this process is perhaps going on, for
Peck shows that in that genus the cross-section of the outer
gill-plate has parallel and straight edges, but that the outer
lamella of the inner has a wavy margin. Posner shows
successive stages of secondary folding in the gills of Pholas
dactylus, Venus (sp), Mya arenaria, Ostrea edulis, Solen
vagina, Cardium edule, Pinna nobilis.
Diametrically opposite, as the views advocated by Posner
and Peck may seem, it is not difficult to reconcile the two.
If we look over the list of the genera examined by Posner,
we shall find all of them, except Mytelus and perhaps Pecten,
to possess more complex gills than Unio, and starting, as he
did, from the last genus, it is no wonder that he considered
608 K. MITSUKURI.
it to possess the primitive gill. On the other hand, Peck
investigated forms simpler than Unio, and arrived at the
probably true conclusion. Posner simply began where
Peck ended. The two investigators, therefore, supplement
each other, and now, with the addition of the extremely
simple gills of Nucula and Yoldia, the series is fairly com-
plete, and it seems to me that the filamentary character of
the primitive Lamellibranch gill is made tolerably certain.
LIMULUS AN ARACHNID. 609
Limu us an ARACHIND. By E. Ray Lanxester, M.A., F.R.S.,
Jodrell Professor of Zoology in University College, London.
(Continued from p. 548.)
Further remarks on the pulmonary sacs and lung books
of Scorpio.—In the comparison of the lung books of Scorpio
and the gill books of Limulus, given in a preceding portion
of this memoir, and in the attempt to derive the two modi-
fications of lamelligerous appendage from a common an-
cestral form, I have carried the supposed history only so far
as to reach a hypothetical Scorpion-like form in which the
lamelligerous appendage is supposed to be filled with blood,
the “ pulmonary sac,” or “ investing sac,” or “cave of in-
vagination ” (the homologue of the funnel-like cavity of the
tendon of the thoraco-branchials of Limulus), being still
filled with air and communicating persistently with the
atmosphere by means of a stigma, which in this case is
the original orifice of invagination of the investing sac.
Such was probably the condition of an ancestral Scorpion.
In living Scorpions a further development has taken place.
The original stigma has become entirely closed up; the in-
vesting sac—that which I have spoken of as pulmonary sac
—contains no longer air but blood. A mew opening (the stig-
matic slit) has formed within the area formed by the ciosure of
the primitive opening of the cave of invagination in the form
of a slit-like fissure in the delicate membranous wall of the axis
of the in-sunken pulmonary appendage (see woodcut, fig. 15).
By this aperture air now enters where, in Limulus and the
J
was
ee
Pune) aay
Fig.15
Fic. 15.—Diagram of a Scorpion’s lung-book, enclosed in the pulmonary
sac and divided by a cut at right angles to the lamelligcrous axis,
ax, axis; 1, lamella; ps, pulmonary sac or cave of invagination; m,
raised margin of the stigma ; s/, slit leading from the exterior into the
axis of the lamelligerous appendage.
610 PROFESSOR E. RAY LANKESTER.
early Scorpion ancestors, there was blood. A blood space has
become converted into an air space just as an air space (that
of the investing sac) has become converted into a blood space.
That a blood space should have become converted into an
air space is not exceptional. All trachez in Arthropoda are
potenttal blood-vessels, and their blood-vessels are potential
trachee. The air-carrying spaces of Arthropoda have been
in fact in many cases probably produced by a direct conver-
sion of blood-vessels.
The changed contents of the Scorpion’s as compared with
the King Crab’s respiratory appendage does not affect the
morphological significance of its parts nor the importance to
be attached to the evidences of its having once projected on
a free surface, although now sunk within asac formed by a
recess of the body surface.
The minute embryological history of the Scorpion’s lung
book is the evidence which we now want in order to actually
demonstrate that the primitive stigma is the orifice of in-
vagination of the investing sac into which the lamelligerous
appendage sinks, and that the opening into the axis of the
appendage from the surface is a secondary formation, pro-
duced after the primitive stigma had been occluded and
completely closed by the adhesion to the lips of that orifice
of the axis of the in-sunken lamelligerous appendage.
So much as is already known of the embryological history
of the Scorpion’s lamelligerous lung sacs is not opposed to
the view here advocated. Rudimentary appendages, which
in the embryo project from the surface of the segments in
which the pulmonary organs are subsequently found, dis-
appear from view at the same time as certain pits are formed
in their immediate vicinity. These pits and their orifices of
invagination are, according to my view, not the air-contain-
ing chamber and its permanent external opening, but the
investing sacs (the homologues of the hollow parabranchial
tendons of Limulus) in which the lamelligerous appendage
is enclosed, and which cease after their formation to com-~
municate with the exterior.
§c. ALIMENTARY CANAL.—Though there are very con-
siderable differences between the alimentary canal and its off-
growths in Limulus and in the Scorpion, yet there are some
remarkable agreements of a fundamental character. The differ-
ences, such as they are, can be viewed as the results of special
adaptation. There is the same difficulty with regard to the
facts relative to the Scorpion’s alimentary system as in re-
gard to all its viscera. I shall rely upon Newport, but I
All
Fig.l6. /
A B \\ ml
: NY op.
Fic. 16.—Diagrams of the nervous system (see page 508); 4 B, of
- Buthus (Scorpion), after Newport. C, of Limulus, constructed from
Milne-Edwards. I to VI, nerves to the cephalo-thoracic limbs; VII,
nerve to the genital operculum; VIII to XII, nerves to the lamelli-
gerous appendages, of which all arise from the ventral cord in Limu-
lus; whilst VIII, IX, and X are, as it were, drawn up to the cwsopha-
geal collar in Buthus. oc, nerve to the compound or grouped eyes ;
oc’, nerve to the simple eyes; Z‘ to L*, position of the four respiratory
appendages of the left side of the Scorpion; g, rectal ganglia of
Limulus ; sp, nerves to the post-anal spine.
612 PROFESSOR E, RAY LANKESTER.
may mention that Dufour (‘ Mémoires de 1’Institut Sciences
Math. et Phys.,’ vol. xiv, 1856,) has given an account
which is based upon the examination of freshly killed speci-
ments of Scorpio occitanus. In regard to the alimentary
canal and its appendages, Dufour is probably correct where
he differs from Newport, the divergence being due to the fact
that Newport studied the large oriental species of Buthus,
whilst Dufour made use of the species above-named. Differ-
ences in the account given by Dufour of the nervous and
circulatory systems are not thus to be explained, and with-
out definitely concluding that Dufour is entirely wrong in
his statements, I have felt justified in accepting Newport’s
account as accurate. Newport, unfortunately,did not complete
his figures of the alimentary system nor give any proper
account of them. Hence Dufour’s contribution to this part
of the subject is of increased value.
In both Scorpio and Limulus the alimentary canal consists
of an axial tube which takes a median course without lateral
convolution from mouth to anus. It presents a suctorial or
ingestive portion in front, and a widened “ proctodzeum,” or
hind-gut posteriorly. The mouth in Limulus is not placed
so far forward as in Scorpio, but has a considerable area of
the cephalothorax in front of it. Resulting from this posi-
tion we find that the suctorial or pharyngeal portion of
the tract is bent sharply upon itself, passing from the mouth
forwards to the front of the head, and then turning upwards
and backwards to pursue a median course to the anus. This
bent pharynx of Limulus is a powerful suctorial organ, and
is lined within by chitinous ridges. The food of Limulus
consists of soft-bodied worms, which are sucked into this
organ and crushed by it.
Corresponding to the bent pharynx of Limulus is the
pharyngeal sac of Scorpio, the mechanism of which was
described by Professor Huxley in this Journal (1860). The
Scorpion’s pharynx is adapted to the sucking up of the juices
of other animals which it kills, but never draws within the
boundaries of its exceedingly minute oral aperture.
Following upon the pharynx of Limulus, and separated
from it internally by a valvular arrangement, is the digestive
portion of the alimentary tract. It is remarkable for pre-
senting two pairs of tubular outgrowths, which are the stalks
of the huge saffron-coloured gland which fills up the space
offered by the horseshoe-shaped carapace, and even extends
into the region of the abdomen. The digestive section of
the alimentary tract runs through the whole series of appen-
dage-bearing segments, and in the telsonic region joins the
LIMULUS AN ARACHNID. 613
proctodzum or anal invagination, from which it is very
sharply marked off by a groove and by the expansion and
plication of the walls of the proctodeum.
Alimentary canal. 4, of Scorpion (Buthus);
after Newport. 2B, of Limulus. ps,
pharyngeal sac; sal, salivary gland ;
c! to c’, glandular ceca of the mid-gut,
A M, Malpighian tube; pro, proctodseum.
The corresponding section of the Scorpion’s alimentary
tract also carries more than one pair of glandular ceca, and
ends in a voluminous proctodzum, which commences, pre-
cisely as in Limulus, in that region of the body which suc-
VOL, XXI,—NEW SEK. SS
614 PROFESSOR E. RAY LANKESTER.
ceeds the thirteenth segment, as indicated by the superficial
sclerites.
Very marked differences, however, exist between the two
animals in regard to the number of the glandular ceca.
Whilst Limulus has but two pairs of ducts opening at an
interval into the mid-gut (mesenteron), the Scorpion has
(according to Newport) six. The first pair are connected
with a peculiar pair of glands recognised by Newport, Dufour
and Huxley (loc. cit.) as salivary glands. The opening of
these ducts is placed at a point where the alimentary canal
is slightly dilated, ‘The following five pairs of ducts are the
conduits of a huge glandular mass, which corresponds unde-
niably to the great saffron-coloured gland of Limulus. But
in Limulus the relative enlargement of the cephalothorax
results in the packing of the gland into that region, whereas
in Scorpio the relative enlargement of the anterior part of the
abdomen (segments VII to x11I inclusive) results in the pack-
ing of the gland more posteriorly. The same difference of
external proportions in the two animals results in a similar
contrast in the position occupied by their generative glands ;
in Limulus they ramify anteriorly to the genital orifice, in
Scorpio posteriorly to it. -
According to Newport, the glandular mass (which I shall
call the hepatic gland, in accordance with custom, and not as
implying that it is the morphological equivalent of the ver-
tebrate liver rather than of any other outgrowth of the
mesenteron) is divided into lobes or lappets, corresponding
to the separate ducts. Dufour also admits this to be the
case for the large oriental species of Buthus, but describes
the organ as continuous, and with only four pairs of ducts
(in place of five) in S. occttanus. The minute structure of
this gland has not been investigated in any Scorpion nor
yet in Limulus. By earlier writers it was spoken of in
Scorpion as ‘‘ the fat body.”
The Scorpions appear, then, to vary in the number of pairs
of ducts possessed by the hepatic gland, and the fact that
Limulus has but two pairs is, accordingly, not an important
point of divergence. The absence of salivary glands is a
more serious departure from the arrangements prevailing in
the Scorpions. It is, however, to be remarked that on com-
paring allied aquatic and terrestial forms of animals, salivary
glands are not unfrequently found to be present in the latter
whilst absent from the former.
When we come to compare the proctodeum of the
two animals we find, perhaps, the most important dif-
ference which can be pointed to as obtaining between
"LIMULUS AN ARACHNID, 615
Limulus and Scorpio. The exceeding shortness of the
proctodzeum of Limulus is only a part of that general reduc-
tion of its hinder segments which is paralleled in many
other groups of Arthropoda, But in Scorpio there are given
off from the anterior border of the proctodzeum two delicate
tubes. According to Dufour, in Sc. occttanus there are four
of these tubes, of which one pair is branched. Newport,
however, figures only one pair in Buthus. These delicate
tubes are the Malpighian glands, found alike in Myriapoda,
Hexapoda,and Arachnida, but never in Crustacea. They have
been shown in Spiders by Mr. Balfour (20) to develop from
the proctodzum, or anal invagination of the epiblast; they
have a renal function, and possibly represent morphologi-
cally ‘ nephridia,’ such as those of Gephyrea and Rotifera.
Their absence from Limulus is a difficulty in the way of
associating Limulus and Scorpio, but itis also a difficulty in
the way of associating the Crustacea with the other Arthro-
poda. Leydig has pointed out, in the proctodeum of Cope-
poda, structural evidence of the existence of a region which
may functionally represent the Malpighian tubes of the
tracheate Arthropoda, and careful histological study may give
similar evidence with regard to Limulus. As to the develop-
ment of actual cecal tubes in this region, two views are admis-
sible: either the common ancestor of the Arthropoda possessed
these tubes and they have been lost by Crustacea and by
Limulus (and some others) among the Arachnida, but
retained by the various tracheate classes, or the common
ancestor possessed only the functional ‘‘renal region” of
the proctodeum, which has remained undifferentiated in
form in Crustacea and in Limulus, but has taken on the form
of czecal tubes in the air-breathing forms, perhaps indepen-
dently, in the course of the evolution of different groups. If
we are to hold that Malpighian tubes can only once have
originated, and that all forms possessing them have a common
ancestor, we must suppose either that Limulus has lost them
or that all Tracheata are descended from the Arachnida.
Amongst these possibilities we have no decisive indications.
The whole question of the genealogy of the various classes of
Arthropoda is involved in the issue.
§ d. VASCULAR SYSTEM.—The close agreement between
the vascular system of Limulus and Scorpio has been ably
insisted upon by M. Alphonse Milne-Edwards, who, eight
years since, gave the results in his beautiful memoir, already
cited, of a series of injections carried out upon perfectly fresh
specimens of Limulus. It is not possible to say, in the
616 PROFESSOR E, RAY LANKESTER.
absence of any adequate investigation of fresh specimens of
Scorpio, how far the resemblance may go; but, depending
upon the careful dissectious by Newport of spirit specimens
(and discarding those of Dufour which are very incomplete),
we are able to point to very close agreements.
In Limulus a more complete vascular system has been
demonstrated than in any other Arthropod, and Scorpio
comes nearest to it in this respect of all members of the
group. The arterial channels do not end in wide spaces
bounded by the connective (vasifactive) tissue which clothes
muscles and viscera, but the connective tissue here, as in
other animals in which fine vessels are developed for the
passage of the blood, forms in most regions of the body a
series of canals, which constitute a capillary system and lead
into definitely constituted veins.
It is worthy of remark by the way that canalisation of the
connective tissue is the same phenomenon and due to the
same processes of growth in all Arthropoda, whether the
canals so formed are connected with the atmospheric air by
stigmata or are filled by the blood fluid of the primitive
ceelomic cavity.
It does not fall within the scope of this memoir to give a
detailed account of the vascular system of Limulus; for that
the reader is referred to the memoir of M. Milne-Edwards.
I shall content myself with drawing attention to the agree-
ment between Scorpio and Limulus in respect of—(1) the
existence of capillaries and veins; (2) of the well-developed
vessels conveying blood to the limbs and viscera, and more
especially in respect of the great spinal artery and its mode
of origin ; (3) of the intimate association of the arteries and
nerves ; (4) of the details of the structure of the heart.
The memoir by George Newport, in the ‘ Philosophical
Transactions’ for 1843, and that by M. Alphonse Milne-
Edwards, in the ‘ Annales des Sciences Naturelles’ of 1873,
contain the exposition of the facts in detail relatively respec-
tively to the Scorpion and the King Crab. Of the latter
animal, M. Milne-Edwards says: “The venous blood, in
place of being distributed in interorganic lacune, as in the
Crustacea, is in a considerable portion of its course enclosed
in special vessels whose walls are perfectly distinct from the
adjacent organs ; they often take their origin in ramifications
of a remarkable delicacy and lead into reservoirs which are
for the most part definitely circumscribed. The nutrient
liquid passes from these reservoirs into the branchie, and
after having traversed these respiratory organs, passes by a
system of branchio-cardiac canals into a pericardial chamber,
LIMULUS AN ARACHNID. 617
and then penetrates the heart. From the heart, the dimen-
sions of which are considerable, it is forced into the tubular
arteries with resisting walls, the distribution of which is
exceedingly complex, with frequent anastomoses, whilst their
terminal ramifications, which are of marvellous tenuity and
abundance, can be followed into the substance of the most
delicate membranes.” ‘These capillaries are figured by M.
Milne-Edwards, but we have not of them, any more than of
the tissues of Scorpio, a satisfactory histological account.
Gegenbaur (2), whose observations were made on spirit speci-
mens, did not observe these finer ramifications of the vessels,
but supposed the arteries to lead into intercommunicating
lacunee without definite walls.
As to Scorpio, it may be justly said that it was the main
purport of Newport’s memoir to make known just such an
extended vascular system in the Myriapoda and Arachnida
as above indicated for Limulus, though M. Alphonse Milne-
Edwards does not cite Newport’s work, but unjustly appeals
to the second-hand authority of M. Blanchard, for the few
facts which he mentions relative to the Scorpion. And
further, the general description of the circulation above
given as to Limulus is strictly applicable as a summary of
Newport’s observations upon the course of the blood and
distribution of the vessels in the Scorpion.
Newport’s description and figures of the heart and its
main arteries in Scorpio show a close agreement with these
parts in Limulus, as described by Milne-Edwards. A revi-
sion of these structures in the Scorpion, in the light of what
is now known as to Limulus, would probably show a still
closer agreement in some details, especially were injection
practised upon freshly killed specimens.
The diagrams here given will enable the reader to judge
of the general features of the arterial system in the two
animals.
The heart of both Limulus and Scorpion is an elongated
organ, constricted so as to form eight successive chambers,
which are imperfectly marked in the Limulus, but more
obvious in the Scorpion, since in that animal imperfect
transverse septa occur within it, less complete, according to
Newport, than in other Arthropod hearts. In front of the
eight chambers the heart is continued in both animals as a
truncus arteriosus towards the head. Posteriorly it is con-
tinued as a posterior aorta in Scorpio into the cylindrical
tail; but in Limulus, in accordance with the reduction of that
region of the body, it ends blindly. The eight chambers of the
Scorpion’s heart appear to be the exact equivalents of the less
618 PROFESSOR E. RAY LANKESTER.
strongly marked divisions of the King Crab’s heart, being
originally placed in corresponding segments of the body. At the
BHM
4
cK
a
a
He HHH @ a
A
Fie. 18.—Heart and origin of the supra-spinal artery. 4, of the Scor-
pion (Buthus), after Newport; B, of Limulus, after Milne-Edwards.
Ito VI, arteries to the six pediform limbs; VII to XIV, the eight
chambers of the heart; sp, supra-spinal artery ; ce, cerebral arteries ;
c, caudal artery ; /, lateral anastomatic artery of Limulus.
anterior margin of each division there is a pair of valvular
apertures, and there are accordingly eight pairs in each
heart. At the hinder margin of each division in the Scor-
pion a pair of lateral arteries is given off (eight pairs in all) ;
such lateral arteries exist only in connection with the first
three divisions of the King Crab’s heart, their place being
taken by secondary longitudinal trunks (woodcut, fig. 19, 2).
From the base of the truncus arteriosus, that is, just in front
LIMULUS AN ARACHNID, 619
of the most anterior pair of valvular apertures, a pair of
lateral arteries is also given off in both hearts.
The eight chambers of the Scorpion’s heart are placed in
the seven anterior abdominal segments, the first correspond-
ing to the segment which bears the genital operculum, the
last two being placed in one segment (thirteenth of the
whole series), the broad triangular segment which precedes
the first cylindrical caudal segment.
The eight chambers of the King Crab’s heart have a
similar relation, though not so obvious. The anterior por-
tion of the heart is somewhat drawn forward, so that the
segments indicated by the valvular apertures are (like the
corresponding nerve ganglion of the genital operculum) a
good deal shifted to the front of the appendicular portions of
the skeleton to which they are segmentally related.
In place of the five hinder pairs of lateral arteries present
in Scorpio, we find in Limulus large lateral arteries (fig. 18 7),
which take origin by an anastomosis from the three pairs of
anterior lateral arteries of the heart, and from the pair of
lateral arteries of the base of the truncus arteriosus.
The truncus arteriosus (or anterior portion of the heart,
as M. Milne-Edwards prefers to call it) presents a remark-
able agreement in the two cases in regard to the distribution
and character of the vessels given off from it, although upon
the basis of a fundamental agreement very wide differences
in detail are to be noted. At the base of the truncus, just
in front of the most anterior pair of valvular apertures of the
heart, we have the pair of lateral arteries similar to those
given off from the heart. Then the trunk is continued
forwards (through the cephalothoracic region in Scorpio),
and gives off two branches, which form a small vascular
collar around the cesophagus in the Scorpion, but a wide
pair of arterial commissures in the King Crab, which meet
upon the postcesophageal portion of the nerve collar. In
front of the vascular collar in Scorpio the trunk divides into
a median and two lateral stems, and from these, arteries are
given to the cephalothoracic appendages, to the brain and to
the eyes, as shown in the woodcut. Its main continuation,
however, is in the vascular collar, the arches of which form
a large vessel which, as the supra-spinul artery, takes a
course backwards along the upper surface of the ventral
nerve-cord (see woodcut, sp.). The association of this part
of the arterial system with the nerve-cord and its branches is
very intimate, so as. to have excited special remark on the
part of Newport.
A parallel but more intimate association of the correspond-
620 PROFESSOR E, RAY LANKESTER.
ing part of the vascular system in Limulus, with its nerve-
ganglion collar, cord, and main nerves, was first observed by
Owen (‘ Lectures,’ 1855), but has been fully demonstrated and
described in detail by Milne-Edwards. The supra-spinal
artery of Scorpio is represented by a complete arterial invest-
ment of the nerve-ganglion collar, including the brain, and of
the chief nerves, as well as of the ventral nerve-cord arising
from it, so that the nerves actually lie izszde arteries and the
brain, nerve-collar and nerve-cord are placed in the interior
of a great arterial trunk corresponding to the supra-spinal
artery of the Scorpion.
The agreement of these parts in Limulus and the Scorpion
has been insisted upon by M. Milne-Edwards at page 19 of
his memoir (8).
No Crustacean presents so complete a vascular system as
Limulus, nor can we find anywhere but in Scorpio an artery
originating by arterial arches embracing the cesophagus and
passing through the body in close association with the nerve-
cord as a main channel for the distribution of the blood.
The chief difference (by no means a small one) between
this part of the arterial system in Limulus and Scorpio is
that the arteries to the cephalothoracic limbs and brain are
in the former given off from the cesophageal vascular collar,
or from its united factors, whilst in Scorpio they originate
from a distinct trifurcate anterior continuation of the dor-
sally placed truncus arteriosus (see woodcut, fig. 19).
§ e. GENERATIVE GLANDS.—The position of the exter-
nal openings of the generative organs has already been
shown to correspond exactly in Limulus and Scorpio, being
placed in both in the segment next following that to which
the sixth pair of leg-like appendages are attached, and being
covered in by an opercular plate with a bifid margin, the
plate being formed by the coalescence of the two appendages
proper to this segment.
Limulus and Scorpio agree in having the sexes distinct.
They also agree in the general form and character of the
ovaries and testes respectively, and in the fact that the
ovary and the testis are in fundamental form like to one
another.
Though it might be possible to find an ovary or a testis
similar in form to those of Limulus and Scorpio among Crus-
tacea (I do not know of one), yet it is an important fact, as
part of our cumulative evidence of affinity between the two,
that in both these animals the ovaries and the testes present
the same characteristic form, and that that form is an unusual
LIMULUS AN ARACHNID, 621
one. The tubular genital gland is not disposed as a simple
central body with two ducts, nor as right and left lobes united
by a central isthmus, nor as a single or double bunch of simple
or arborescent ceca, but it is distinctly retiform. There
are two genital ducts, which pass from the two genital pores
right and left, and are continued into a widely diffused
meshwork. ‘The meshwork may be regarded as a continua-
tion of the two genital ducts which give rise to branches,
which anastomose and also join their fellows of the opposite
side ; it hasa tubular structure, and its walls present follicles
in which the generative cells are produced. In Scorpio the
ovarian follicles are less numerous and more highly developed
individually than in Limulus, and also in the former animal
the meshwork formed by the gland is more symmetrical and
its meshes larger than in the latter, but the reticular arrange-
ment of the genital gland is the same in both.
The main differences in the genital glands of Limulus, as
compared with those of Scorpion, are related to two modifying
causes : firstly, the greater relative size of the cephalothorax
in Limulus; and, secondly, the terrestrial mode of life of
Scorpion which replaces the aquatic mode of life of Limulus.
Owing to the first of these causes we find that, whereas
in Limulus the retiform generative gland extends both in
front of and behind the genital pore, that is to say, into the
cephalothorax (segments 1 to 6) and into the abdominal
segments (segments 7 to 13), in Scorpio we find its mesh-
works spread entirely inthe region posterior to the genital pore,
that is, in the wide and thick abdominal segments (7 to 18).
The second cause has brought about a very important
difference in the secondary arrangements of the generative
system. Limulus does not copulate, but the male discharges
the spermatozoa into the water on to the surface of the eggs
which have just been laid by the female. Such a method of
fertilisation is impossible in any animal of strictly terrestrial
habits. Copulation is a necessity in such animals. It is
only those terrestrial animals which pass into the water
during the breeding season which can dispense with intro-
mission. Accordingly we find the efferent ducts, both in
male and female Scorpions, modified to subserve copulation.
The ejaculatory apparatus in the male is complicated; the
distal portion of each of the efferent ducts is modified so as
to form an intrommittent organ, and accessory glands are
developed from its sides. The two oviducts in the female
are enlarged to form vagine. There are thus two penes and
two vaginez in the male and female Scorpion respectively.
In copulation the female appears to lie upon her back and,
\
622 PROFESSOR E. RAY LANKESTER.
it has been suggested, with much plausibility, that the
pectens (the lamelliferous appendages of the eighth segment)
serve as tactile organs, guiding and stimulating the move-
ments which result in the coitus.
The female Scorpion is even further specialised in
reference to its genitalia as compared with Limulus. Whilst
it retains the reticulate gland and the ¢wo ducts, each with
its external aperture as in Limulus, it develops no special
spermatheca or receptacle for the spermatozoa received in
copulation, but the semen passes along the tubular oviduct
and into its net-like branches. Here the semen fertilises the
ova, which are placed in follicles set upon the sides of the
mesh-forming ovarian tube. The development of the egg pro-
ceeds actually within the follicle and the Scorpion produces
her young in the living condition.
Connected with this viviparous character is the specialisa-
tion of the egg-bearing follicles carried by the ovarian mesh-
work. In Limulus more numerous eggs are produced, and
there is no specialisation of follicles, but from all parts of
the ovarian reticulum egg-cells appear to develop and to
become free in the lumen of the tubular structure of which
the reticulum consists.
The best account extant of the generative organs of the
Scorpions appears to be that of Dufour (loc. cit.), who
studied fresh specimens, but his account leaves everything to
be done in respect of the histology, and one may even hesi-
tate to feel confidence in his description of large features.
There is, also, no complete account of the generative
glands of Limulus. We may hope that the American
naturalists, who have abundant Limuli on the sea-shore, will
soon give us a precise account of the form of the fully
developed ovary and testis, as well as an account of their
histology. At present our knowledge is confined to the
figure given by Owen of a portion only of the ovary, and to
his description, which is very definite as far as it goes, and
sufficient for the purpose of a general comparison with
Scorpio. The testis was immature in a male specimen
recently dissected by me, and in an earlier dissection I was
unable to clear out this organ fully on account of the special
objects which I had in view.
I was, however, able on that occasion to determine an
important point of agreement between Limulus and Scorpio,
namely, in regard to the character of the spermatozoa. Itisa
familiarfact thatthe spermatozoa of the Arthropoda exhibit the
greatest diversity of form, and also great want of uniformity,
as to the presence or absence of a motile flagelliform ‘tail.
/
/
LIMULUS AN ARACHNID. 623
In Crustacea generally they are immobile and of very various
shapes; but in Cirrhipedia, and possibly some others, they
are filamentous, with a motile tail. In chilopod Myriapods
they have a vibratile tail. In Chilognaths they are motion-
less. In hexapod Insects they have a vibratile tail. In some
Arachnida (e.g. Spiders) they are devoid of such a process.
We owe to Kolliker the observation that in the Scorpio
europeus the spermatozoa are filamentous in form, with a
vibratile tail. Accordingly, it is compatible with Arach-
nidan affinities for the spermatozoa to be either motile or
immobile ; at the same time, as an element in the cumulative
evidence of affinity between the King Crab and Scorpion,
which it has been my object in this essay to bring together,
the presence of vibratile spermatozoa in Limulus is a fact
of value. The spermatozoa of Limulus are, as I observed
four years ago (4), provided with a long vibratile tail; they
agree, therefore, with those of the Scorpion.
C. Tor Euryprerina AS A ConneEcTING LINK
BETWEEN LIMULUS AND SCORPIO.
The intimate affinity of the extinct Eurypterina with
Limulus is no longer doubted. The researches of Hall,
Huxley, and Woodward, have thoroughly established the
fact that Pterygotus, Kurypterus, Slimonia, and Stylonurus,
are to be regarded as Limuli, in which one pair of leg-like
organs (probably the most anterior) has been suppressed,
and in which the telsonic region, instead of exhibiting but an
imperfect development of segments posterior to the twelfth,
and that only in the embryo, gives rise to a series of segments
forming a large tail-like region of the body. The result of
this development of segments between the anus and the last
appendage-bearing segment (the twelfth of Limulus) is that
the so-called “ macrourous ’’ form of body is produced, and
consequently a general similarity in appearance is observed
between the Eurypterina and Scorpio.
The two woodcuts (figs. 19 and 20) sufficiently exhibit
this general resemblance. In other respects, allowing for
the suppression of an anterior pair of appendages in the
Eurypterina, we find obvious agreements with Limulus.
The actual fifth pair of limbs—theoretically the sixth—
present constantly in all the genera that enlarged form and
specialisation of their terminal joints which are noticed in
the corresponding limbs of the King Crab. The coxe of
these and of the three pairs of limbs in front are brought up
to the mouth, and denticulated so as to serve as jaw-organs,
624 PROFESSOR E. RAY LANKESTER,
A genital operculum of the same proportions as that of
Limulus is present, and traces of appendages (sternal plates),
corresponding to the five pairs of branchial plates of that
Fic. 19.—Pterygotus Angticus. The segments are numbered to show their
agreement with those of the Scorpion (see Fig. 2). oc, compound
eye; ch, chilarium; gez, genital operculum ; az, anus ; PA, post-anal
spine or plate.
Fia. 20.—Slimonia acuminata. oc, compound eye, lateral; oc’, simple eye,
central; PA, post-anal spine.
animal, have been detected on the following segments. The
cephalothoracic tergum is, in some Eurypterina, horseshoe
shaped as in Limulus, though relatively smaller in size, and
the eyes appear to have been similar to those of Limulus
in character and position, though the compound eyes are
close to the margin of the carapace instead of at some distance
from it. Though in many Eurypterina the cephalothoracic
appendages are simple tactile or ambulatory organs, yet in
others we find (as in Pterygotus) the chelate form appearing,
as with the majority of these limbs in Limulus.
I am anxious here to point out that there is not only a
general resemblance of the Eurypterine body to that of the
Scorpion, but that in many of the most important points in
which they differ from those of Limulus the Eurypterine
body and appendages agree precisely with those of the
Scorpion, and not in a merely general way, The Kuryp-
LIMULUS AN ARACHNID. 635
terina in fact serve in a most important manner to directly
confirm the assimilation of segments and appendages in the
two animals which I have already insisted upon.
In the first place, it is to be admitted once for all that
Limulus and Scorpio agree with one another, and differ
from the Eurypterina in possessing six pairs of cephalo-
thoracic appendages. “An anterior pair has disappeared in
the Eurypterina, and this reduction is the distinctive cha-
racter of the order. That such a loss of an anterior pair of
limbs has occurred is rendered probable by the fact that
there is evidence of a tendency for this abortion of anterior
appendages to go on further still. The actual anterior pair
corresponding to the second pair of Limulus and Scorpio is
very small in some Eurypterina (see fig. 20), and suggests the
existence of causes tending to the suppression of appendages
in the anterior region. Such a suppression of anterior ap-
pendages is not without parallel among the Arthropoda (e.g.
certain Crustacea), and for the Arachnida it has always been
regarded as characteristic whenever the attempt has been
made to compare the appendages of those forms with those
of either the hexapod Insects or of the Crustacea. It is not,
therefore, assuming too much when we admit that just as
possibly (though I do not at the moment assert the fact)
one pair of appendages is suppressed in all Arachnida as
compared with other Arthropoda, so a second pair has been
suppressed in the Eurypterine order of Arachnida.
Counting the segments of the Eurypterina upon this
assumption, we find that they exactly agree with those of
the Scorpion. The segments succeeding the cephalothorax
and anterior to the anus are twelve in number, gradually
towards the anus, though not suddenly, diminishing in size
after the seventh, as in Scorpio. Posteriorly to the anus
is the postanal spine, broad and flat in most Eurypterina
for swimming, and neither rod-like, as in Limulus, nor
globose, as in Scorpio. Any difficulty which the unseg-
mented telsonic region of Limulus may have presented in
the comparison with Scorpio is removed by the simple
inspection of the abdomen of the fossil Limuloid (woodcut,
fig. 20).
Secondly, a difference between Scorpio and Limulus of
some importance is seen when the form of the cephalo-
thoracic limbs is compared, since in Scorpio certain of
those which are chelate, in Limulus are simple ambulatory
organs. Here, too, the admittedly Limuloid Eurypterina
remove all difficulty; for among them all the cephalo-
thoracic appendages are in some genera non-chelate (fig. 20),
626 PROFESSOR E, RAY LANKESTER.
and exhibit a considerable range of character, being (as in
other Arachnida) either ambulatory or tactile organs. The
chelate limbs are thus seen to be a special feature of Limu-
lus, and not essentially characteristic of the Limuloid Arach-
nida. Accordingly there is no difficulty in deriving the
Scorpion’s ambulatory limbs from those of such Limuloids.
Thirdly, certain features are presented by the cephalo-
thorax of the Eurypterina, in which they agree very closely
with the Scorpions, and in which Limulus differs from them.
A great difference between Limulus and Scorpio, leading
to differences in the form and size of internal organs, is that
presented by the much greater size of the cephalothorax in
Limulus. Among the Eurypterine Limuloids we find, how-
ever, genera, in which the cephalothoracic carapace has
precisely the quadrangular shape and small relative size, as
compared with the abdomen, which is noticed in Scorpion
(fig. 20). It cannot be doubted that the packing of the
viscera was correspondingly affected, and there is great pro-
bability that the liver was connected by more numerous
ducts with the intestine in these forms (as in Scorpion)
than it is in Limulus. It is also probable in the very
highest degree that the generative glands were developed in
these Eurypterina posteriorly to the genital pores, and not
anteriorly, as in Limulus.
Further, the disposition of the eyes on such a quadran-
gular carapace as that of Slimonia (fig. 20) is singularly
like that seen in the Scorpion. Centrally are two small
simple eyes, oc’, and precisely in the position which they
occupy in Scorpion, viz. at the anterior lateral margin of the
carapace, right and left, are groups of eyes, oc. In the
Eurypterina, as in Limulus, these groups are close set in
composition, so as to form what is called a compound eye,
whereas in Scorpio the individual members of the group are
separate.
The individual factors of the compound eye of Limulus
are more archaic in their histological structure than are the
simple eyes of spiders, but at present we do not know the
minute structure of the grouped eyes of Scorpio. It is
possible that they may show closer agreement with the
Limulus eye than do those of Spiders; or, again, it 1s not
difficult to suppose that from a loose aggregation of very
simple marginal eyes, which existed in the common ancestor
of Limulus, Eurypterines, and. Scorpio, there has been de-
veloped, on the one hand, by coalescence, the compound eye
of the former; and on the other hand, by individual elabora~
tion, the separate eyes of the modern Arachnid.
LIMULUS AN ARACHNID. 627
Lastly, in regard to that element of the sternum which in
Buthus is the pentagonal “thoracic metasternite,” and in
Limulus forms the “chilaria” or paired metastoma, the
Kurypterinesserve to tie Limulus more tightly to the Scorpion.
The duplicate character of the chilaria of Limulus renders
it at first difficult to admit that they are represented by a
single median plate in Scorpio. This right-and-left cha-
racter even led M. Alphonse Milne-Edwards to ignore the
position of the genital apertures and to identify the chilaria
of Limulus with the pectens of Scorpio. The Eurypterines
show clearly enough (evenin the absence of embryological
evidence) the sternal nature of the King Crab’s chilaria,
for they possess, just where thechilariaof Limulus are found,
a single broad oval plate, which rises up from the surface in
such a way as partly to cover in and work as lower lip to
the four pairs of coxal jaws in front of it (see woodcut, fig.
19 ch). This single metastoma, or chilarium,is readily under-
stood also as the equivalent of the single pentagonal sternite
of Scorpio, which is dwindled in size and pushed away in
that animal from the functional jaws by the large ankylosed
coxe of the fifth and sixth pairs of cephalothoracic appen-
dages.
D. Review oF Opinions oF MopERN AUTHORITIES AS TO
THE AFFINITIES OF LIMULUS.
So far in preceding pages my object has been to point out
definite points of special resemblance between Limulus and
Arachnids, especially the Scorpion. I have not paused to
insist upon the absence of any such special agreements
between Limulus and the Crustacea. I propose briefly to
do this now by examining the statements of those who have
asserted that any such special agreements exist.
Clearly between Limulus and any other Arthropod there
must exist agreements which are the common characters,
more or less, of all Arthropods. It may also be possible to
find structural features which are exhibited only by Limulus
and by Crustaceans, one feature finding its parallel in one
Crustacean and one in another. But I think it must be
definitely conceded (1st) that there is no one Arthropod in
which anything like so large a number of the structural
features found in Limulus are paralleled as the Scorpion, and
(2nd) that there are several structural features exhibited by
Limulus which have no parallel in the Crustacea at all, but
are common to Limulus and the higher Arachnida.
Putting together Limulus and the Eurypterines we may
628 PROFESSOR E. RAY LANKESTER,
briefly summarise their agreements with Arachnida and
disagreements with Crustacea as follows:
1. Limulus and the Eurypterines (the one supplementing
the other) agree precisely with the Scorpion in the existence
of eighteen segments expressed in the structure of their
bodies, and in the distribution of these segments into three
groups of six each, viz.: a leg-bearing cephalothoracic region,
an anterior abdominal region, in which each segment carries
lamellate appendages, anda posterior abdominal region devoid
of appendages, ending with the anus and a postanal spine.
No Crustacean presents this number and grouping of its con-
stituent somites.
2. Limulus and the Eurypterines agree with the Scorpion
precisely in the position of the genital aperture beneath an
opercular plate formed by the coalescence of the seventh pair
(in Eurypterines the actual sixth pair of appendages). No
Crustacean has the generative orifice so far forward, and in
none is there a genital operculum of the kind having such
relations of position to the genital apertures.
3. They agree with the Scorpion in the character and
position of the mouth and upper lip.
4. They agree with the Scorpion in possessing a meta-
thoracic sternite, in the possession of a fibro-cartilaginous
entosternite, and in the precise form and relations of that
organ. No Crustacean possesses an entosternite or any
structure resembling it.
5. They agree with the Scorpion in the disposition of
central (single) and lateral (grouped) eyes on the cephalo-
thorax. No Crustacean has an identical arrangement of
single and grouped eyes.
6. Limulus agrees with the Scorpion in the form of the
alimentary canal and its lateral outgrowths (liver), which are
more than one pair. In Crustacea it is very exceptional to
find more than one pair of such diverticula, though a single
pair may carry numerous secondary branches.
7. It agrees with the Scorpion in possessing a supra- or
circum-medullary (spinal) artery, which arises from the dorsal
aorta by two arches embracing the esophagus. No Crus-
tacean has such a supra-spinal artery so originating.
8. It agrees with the Scorpion in the form of the genera-
tive glands. No Crustacean has its generative glands in the
form of an anastomosing network.
9. It agrees with Scorpio in possessing vibratile sperma-
tozoa. No Crustacea except Cirrhipedia are known to have
vibratile spermatozoa.
10. It agrees with Scorpio and Spiders in having a brain
LIMULUS AN ARACHNID. 629
which (like that of the embryo Scorpion and Spider) supplies
only eyes and integument with nerves, and not any appendage.
In all Crustacea, except some Phyllopoda, such an archi-
cerebrum does not exist ; but even in young stages the brain
is found to supply at least one pair of appendages as well
as the eyes.
11. It agrees with Scorpio in the concentration of the
origins of nerves supplying the anterior part of the abdomen,
in the cephalothorax in the form of a nervous collar, per-
forated by the pharynx. Sucha nerve-collar has its parallel
in Crustacea among the brachyurous Decapoda, which, how-
ever, are in other respects the Crustaceans which least
resemble Limulus.
The points in which Limulus agrees with the Crustacea
and differs from Arachnida are three only. They are as
follows :
1. Limulus agrees with many Crustacea, and differs from
Arachnida, in that its respiratory organs are adapted to an
aquatic in place of an aérial medium.
2. Limulus agrees with Crustacea, and differs from Arach-
nida, in that it possesses a pair of groups of eyes, in which
the association of the individual eyes of each group is so close
as to constitute a compound eye.
3. Limulus agrees with Crustacea (excepting some Iso-
poda ?),and differs from Arachnida, in mot possessing glandular
ceca (the Malpighian tubules) growing out from the
proctodzum.
The first of these agreements is purely one of functional
adaptation. The lamelligerous organs of Scorpio and the
Spiders act upon atmospheric oxygen, as might be expected
in animals living on dry land. The fact that the corre-
sponding organs of Limulus respire the oxygen dissolved
in sea water, as do the gills of Crustacea, does not even
remotely tend to establish a morphological agreement between
Limulus and Crustaceans. All attempts to associate organ-
isms in one genealogical group on account of an agreement
in the ultimate mode of performing such functions as respira-
tion and locomotion, without reference to the exact nature
of the organs by which those functions are performed, are
liable to serious error. We cannot, as a principle, associate
in genealogical classification all animals that breathe air,
or all animals that breathe water, or all animals that fly,
or all animals that swim, or all animals that walk. On
the contrary, we must hold the actual structure and ana-
tomical relations of organs to be the only guide to the genetic
affinities of the animals which possess them, quite irrespec-
VOL, XXI.—NEW SER. TT
630 PROFESSOR E, RAY LANKESTER,.
tive of the special adaptations of those organs to an aquatic
or aérial mode of life.
The second agreement, viz. that as to the existence of
compound eyes, is more apparent than real; for it is quite
obvious that a coming together of simple eyes might at any
stage in the evolution of Arthropods produce a compound
eye, whilst further in the actual details of structure of its
compound eye, Limulus is altogether unlike the Crustacea.
The resemblance of the compound eyes in the two cases is a
superficial one, due to homoplasy.!
The third agreement is of a purely negative character.
Limulus and the Crustacea may have independently lost the
Malpighian tubules which were perhaps possessed by the
earliest ancestral Arthropods ; or, on the other hand, these
organs may have developed for the first time in the terrestrial
Arachnida, and have been derived from them by the other
Arthropoda which possess them (Hexapoda, Myriapoda) ; or,
again, the latter may have also developed such organs de
novo. In any case their absence from Limulus is no evidence
of affinity to Crustacea. It is to be noted that the smaller
terrestrial Arachnida are also devoid of these organs.
It will now be convenient briefly to point out and criticise
some of the views which have recently been expressed as to
the affinities of Limulus.
Dohrn (1), in 1871, whilst pointing out at some length
the affinities of Limulus and the Eurypterina, originally
suggested by MacCoy and placed on a firm basis by Hall,
and also whilst demonstrating some of the relationships of
the larve of Limulus to Trilobites, proposes to unite these
forms in one group—-Gigantostraka (a name originally pro-
posed by Haeckel for the Eurypterina alone), and to place
this group near the Crustacea, not absolutely within that
class. |
Although Dohrn cites the views of Straus Durkheim, he
does not support them, and definitely states that we are not
in a position to say what may be the relationships of Gigan-
tostraka to Arachnida.
Dohrn holds that the first pair of appendages of Limulus,
though not the second, is innervated from the cerebral gan-
glion, but he is free from the erroneous conception of the post-
anal spine of Limulus as representing a series of segments.
At the same time he failed to be struck with the exact
identity in the number and disposition of the segments
which is revealed when Limulus and the Eurypterina taken
1 See ‘Annals and Mag. of Nat. Hist.,’ July, 1870, on the use of the term
“ Homology.”
LIMULUS AN ARACHNID, 631
together, on the one hand, are compared with Scorpio, on the
other.
Claus (14), as late as 1881, adopts exactly Dohrn’s view
of the systematic position of Limulus. He accepts the
group Gigantostraka (including Merostomata and Xipho-
sura), and places it as a division of the class Crustacea, in
opposition to the Eucrustacea, consisting of the great sub-
classes Entomostraca and Malacostraca. Of the relationships
of the Gigantostraka to Arachnida, Claus says nothing.
Owen (7), in his monograph on the King Crab, discusses
Dohrn’s views and brings to the question a large mass of
anatomical and paleontological fact. His conclusion that
Limulus exemplifies “ that lower condition of the Crustacea
which has been expressed by the term Entomostraca,” is
vitiated by the fact that although one of the first to recog-
nise that the “‘ chilaria”’ are sternal elements and not appen-
dages, he yet seeks for the representatives of missing body
segments in the postanal spine, and, above all, it is falsified
by his adhesion to the opinion of Van der Hoeven, that
two pairs of appendages are innervated from the cerebral
ganglion. That no appendages are so innervated is now
demonstrated by the dissections of A. Milne-Edwards which
I have confirmed ~ Accordingly, Professor Owen would now
probably be amongst the first to admit the affinities of
Limulus with the Arachnida, since he observes: ‘ If it
were a fact that in Limulus only the foremost pair of limbs
was innervated from the supercesophageal ganglion, the rest
deriving their nerves from the abdominal ganglionic chain,
the advocate for its elimination from the Crustaceous class
would have an argument of weight for the affinity of Limulus
and its extinct allies with the Scorpion and the Spider.”
Huxley (16), who has at various times approached the
question of the affinities of Limulus, holds that it has
relationships, on the one hand, through the Eurypterina to
the Copepod Crustaceans, and on the other hand, to the
Phyllopoda through the Trilobites, and again independently
to the Scorpion. At the same time he definitely places it
in the class Crustacea in the order Merostomata, together
with Eurypterina and the Trilobites. Presumably this
implies that Limulus is a nearly related representative of an
ancestral form which gave rise to the Copepods as one
branch, to the Trilobites and Phyllopoda as another, and to
the Arachnida as a third.
Without discussing for the moment the possibility of any
close connection between the Phyllopoda and Trilobites, |
may remark that the connection of Limulus and the Eury-
632 PROFESSOR E, RAY LANKESTER;
pterina with the Copepoda appears to me to have only the
support of a certain resemblance of general form in its
favour, such resemblance of general form being one which
frequently recurs in the Arthropod series, and has the signi-
ficance merely of a homoplastic agreement, @.e, is a like
moulding of readily modifiable parts brought about quite
independently in the cases compared by the operation of like
adaptive causes. Other examples in relation to. the Eury-
pterina have been previously cited by Professor Huxley
(‘Lectures on Nat. Hist.,’ 1857), e.g. the Cumacea and the
Zoea of some Decapods. I cannot find, on comparing a
Copepod, on the one hand, with the full organisation, on
the other, expressed by a combination of the characters of
Limulus and the Eurypterina, any points which appear to
me indicative of close affinity; the agreements are such as
either are common to the majority of Arthropods or are
agreements of general form, of a nature similar to those
which exist between the macrurous Arachnida and the
macrurous Decapod Crustacea. Such agreements as exact
coincidence in the position of the genital apertures, in the
number, form, and grouping of the appendages, in the dis-
position of the eyes, in the development of sternal plates,
and over and above the individual agreements such intimate
connection as is implied by the multiplied significance of
the combined occurrence of two, three, or more of these
agreements, cannot be established as between the Copepoda
and Limulus.
Between Kurypterina and such Copepoda as Cyclops, there
is a general resemblance of the form of body. We find a
broad carapace covering segments bearing five pairs of
limbs, followed by a tapering series of segments, of which
the anterior carry limbs, and may be distinguished as a
separate region from those which follow. But whilst the
Copepod body terminates in a characteristic furcal postanal
process, the Eurypterina present, like the Scorpion and
King Crab, a single spine or plate. The number of seg-
ments succeeding the carapace in the Copepoda is at most
ten ; in the Eurypterina it is, as in the Scorpion, twelve.
Most significant is the position of the genital apertures,
which in Limulus (and presumably in the Eurypterina) is
placed on the first segment succeeding the six-segmented
carapace, whilst in the Copepods the whole series of five
segments, bearing swimming feet (which would be compared
to the lamelligerous feet of Limulus), intervene between the
carapace and the genital segment. In structure and posi-
tion the eyes on the carapace of Copepods have no resem-
LIMULUS AN ARACHNID, 633
blance to the central and lateral eyes of Limulus, the
Kurypterina, and the Scorpions.
When we examine the appendages, one striking resem-
blance is seen between the males of some free-living Cope-
pods, on the one hand, and Limulus and Pterygotus, on the
other. The first pair of appendages is in these forms pre-
hensile. No other Arthropods except Arachnida have
such a form of the first appendage. But many Eurypterina
have non-chelate anterior appendages (see fig. 20), and the
comparison of appendages in various Crustacea shows clearly
that such a modification is readily acquired and readily sup-
pressed. In one other respect some appendages of some
Copepoda appear to resemble those of Limulus, viz. in the
union of the basal portions of the swimming feet. In
Limulus, however, this union is effected rather by the
upgrowth of a median sternal process than by the coales-
cence of the bases of the appendages themselves.
In other respects the appendages of Copepoda are quite
unlike those of Limulus and the Eurypterina in form, and
they do not agree with them in number. Those near the
mouth have jaw-like coxz, as in all Crustacea, but they, have
the usual Crustacean elements of endopodite, exopodite and
epipodite more or less clearly developed, and are not simple
rami, as are those of the Eurypterina. What may have been
precisely the character of the limbs on the segments following
the carapace in Eurypterina we do not know, but there is
reason to suppose them to have been lamelligerous, and that is
their distinguishing feature in Limulus. No such lamel-
ligerous appendages are known in Copepoda, but in the region
which might be compared to that carrying the genital
operculum and the five lamelligerous appendages of Limulus
—were it not for the fatal difference indicated by the reversed
position of the generative orifices—we find four or five pairs
of simple biramose swimming feet.
In internal organisation there is nothing in the characters
of the nervous, digestive, reproductive, or circulatory organs
(such as are present) of the Copepoda to suggest an alliance
with Limulus, whilst the presence in the former of the
characteristic Entomostracous shell-gland marks a special
divergence between them. It is true that Packard has
assimilated a brick-red coloured structure occurring at the
base of the cephalothoracic limbs of Limulus to a shell-
gland, or to a renal organ. In this I cannot agree with
him. It is not even apparent, at present, that this brick-
red organ, which I have examiued, is of a glandular nature
at all,
634 PROFESSOR E. RAY LANKESTER.
In his ‘Manual of the Anatomy of Invertebrate Animals’
Professor Huxley has recognised the possibility of the rela-
tionship of Limulus to Scorpio as well as to Copepoda, and
has also instituted a comparison between the appendages of
Limulus and those of the Podophthalmous Crustacea.
He considers only one pair of appendages of Limulus to
be innervated from the cerebral ganglion, and regards the
chilaria as the seventh pair of appendages, whilst he asso-
ciates the genital operculum (his eighth pair of appendages)
with the cephalothoracic carapace instead of with the
abdominal carapace. In these respects recent investigations
have necessitated a change of view (as I have explained at
some length above), and accordingly the comparisons based
upon the earlier view of the facts are erroneous. Thus,
Huxley identifies the first pair of appendages of Limulus
with the antennules of Astacus, and regards it as absent in
Scorpio. The second pair he identifies with the antennee of
Astacus and with the cheliceree of Scorpio, the third pair
with the mandibles of Astacus and with the great chel of
Scorpio, the fourth and fifth with the two pairs of maxille
of Astacus and with the two first walking legs of Scorpio,
the sixth (the digging leg) of Limulus with the first
maxillipede of Astacus and the third walking leg of Scorpio.
The chilaria or metathoracic sternites, which are considered
by Huxley as the seventh pair of appendages, he identifies
with the second maxillipedes of Astacus and with the fourth
walking leg of the Scorpion, whilst the genital operculum is
identified with the third pair of maxillipedes of Astacus and
with the genital operculum of Scorpio.
The comparison of Limulus with the Podophthalmous
Crustacean appears to me one which, in reality, it is not
possible to carry out so as to establish any identities, or
plausible points of contact. Even when we reckon the
“ chilaria”’ as appendages we find divergence and difference
as the result of the comparison ; but when these are removed
from the series there is an absolute want of any relation in
the grouping of the appendages compared. Not so with
the Scorpion. Professor Huxley, in consequence of his view
as to the nature of the chilaria, is obliged to assume that
the chelicere of the King Crab are something over and above
what is present in the Scorpion, and thus, eventually, in
counting down the segments, he brings the genital operculum
of the one into coincidence with that of the other. But
when the chilaria are removed from the series offered by
Limulus there is no need to assume an existence of extra
appendages in front in that animal; the whole series in
LIMULUS AN ARACHNID. 685
the two animals compared, viz. Limulus and Scorpio, are
found, on inspection, to be identical in general form and
relation from one end of the body to the other.
It is not possible, it should be observed, to maintain both
positions. If the identification with the parts of the Scorpion
is maintained, then all assimilation of the appendages and
regions of the body of Limulus to those of a Podophthalmous
or of a Copepodous Crustacean must be abandoned. There
is no contact whatever between Limulus and Astacus until
a common ancestral form is reached which exhibited in the
most generalised condition the segmentation and appen-
dages which are the common inheritance of all Arthropoda.
It appears to me quite impossible to assume that this
ancestral form had the characters of the Podophthalmous
Crustacea. Such differentiation and numerical grouping of
appendages as are seen in that highly developed Crustacean
order are of late appearance, and accordingly such forms as
Astacus and Homarus should not be made use of as standards
of comparison representative of the Crustacea, but less differ-
entiated examples must be sought. On the other hand,
when we find it possible to establish a series of agreements
between a form of doubtful affinities, such as Limulus, and
a highly differentiated Arthropod, such as the Scorpion, the
closeness of the genealogical connection thereby proved is
greater in proportion as the differentiation of the forms
compared is high, and as the number of points of agreement
are numerous.
The two authors who have had the facts in reference to
Limulus and Scorpio most fully before them (since some
of the more important were established by their own re-
searches), and yet have not drawn the conclusion from those
facts to which it seems to me that they necessarily lead, are
MM. Alphonse Edwards and Dr. A. 8. Packard. M.
Alphonse Milne-Edwards, although he showed that the
cerebral ganglion of Limulus was unlike that of the Crus-
tacea, could not admit of its assimilation to that of the
Scorpion, not being acquainted, apparently, with Metschni-
koff’s observations on the development of the latter animal ;
and although he recognises the similarity of the perineural
arterial system of Limulus to the supraneural or “spinal”
arterial system of Scorpio, yet he is led away from the
assimilation of the two animals by holding to the strange
notion that the chilaria of the King Crab placed just in front
of its genital operculum are the homological equivalents of
the pectiniform appendages of the Scorpion placed just
behind its genital operculum. M. Milne-Edwards places the
636 PROFESSOK E, RAY LANKESTER,
Limuli neither with the Arachnida nor with the Crustacea,
but in a group apart. The fact that this investigator did
not attempt a complete study of the skeleton of Limulus,
and a comparison of that and other organs with the corres-
ponding parts of the Arachnida, Kurypterina, and Crustacea,
sufficiently explains the conclusion at which he arrived.
He confessedly made use of but few data, and those such as
he himself brought to light in the case of Limulus. The
value of his contributions to our knowledge of the ana-
tomical structure of the King Crab are not in any way
diminished by the vulnerability of the conclusion which he
based upon them.
With regard to the conclusions of Dr. A. 8. Packard, it
is difficult to avoid an expression of surprise. We owe to
Dr. Packard the important observation of the late appear-
ance of the chilaria, and other observations as to the seg-
mentation of the telsonic region in the young Limulus, and
the primitive connection of the genital operculum with the so-
called abdomen rather than with the cephalothorax. He has
probably seen more of young and old King Crabs than any
other naturalist, and yet, writing in 1880 (No. 9), with all
the literature before him, with all the facts under his hands,
he still maintains that the Limuli are Crustacea, examines
the aphoristic statements of Van Beneden to the effect that
they are Arachnida and rejects them. Dr. Packard simply
adopts from Dohrn the group of Gigantostraca as Claus has
done, and as Gegenbaur has done; but whilst Gegenbaur
uses for it the old term Peecilopoda, Packard thinks it
necessary to bestow upon it the new name Paleocarida.
An examination of Dr. Packard’s latest memoir on
Limulus will, I think, show that he clings to the notion
that Limulus is a Crustacean, and is unable to perceive that
its true place is among Arachnida, because he entertains
certain erroneous preconceptions as to the value of the
various parts of an arthropod body as indicative of genetic
affinity. A respiratory appendage, however, unlike in
structure to anything seen in Crustacea, is, if it acts as a
branchia, to be considered as “ of the Crustacean type ”
according to Dr. Packard. This is a simple confusion of
logical categories. It is true that many Crustacea have
branchial appendages, but it does not follow as a conse-
quence that all branchial appendages are borne by Crusta-
ceans, or that such appendages are of “the Crustacean
type.” So too Dr. Packard speaks of “ true antenne ” and
a ‘true mandible,” “a thorax,’ and “an abdomen,” ag
though these were recognised and definable elements o¢
LIMULUS AN ARACHNID, 637
arthropod structure, instead of being as they are descriptive
terms devoid of homological significance. Really what Dr.
Packard’ has to deal with is a series of segments and a
series of appendages, and he can only compare those of one
animal with those of another by taking them in numerical
sequence. When an author allows himself to set up such
intangible criteria as are involved in Dr. Packard’s distinc-
tion between “true” and “false”? antenne, he clearly
opens the way to any conclusion he may fancy, and may
colour a picture as he may choose by the use of these
epithets.
Dr. Packard’s estimate of the significance and import of
parts in the attempt to determine the affinities one with
another of various Arthropods, is, it seems to me, fallacious,
owing to the fact that it is based upon an old-fashioned
morphology. ‘Though he makes use of the phrasevlogy of
the doctrine of evolution, and constructs genealogical trees,
he has “ the doctrine of types” at heart, and meets a matter
of fact question in morphology by the use of such phrases
as the “crustacean type,” the “ tracheate type,” and the
*‘ hexapodous type.” With such phrases no critic can pos-
sibly deal, for no one can say what Dr. Packard means by
these ‘‘ types.” We are told by him that the Arachnida
have their mandibles and maxille ‘‘on hexapodous type,”
whilst the Merostomata (Limulus) have ‘‘only their mor-
phological equivalents (Guathopods).” This is meant to
appear as though a wide divergence between the Scorpion
and King Crab were being in so many words established,
and to Dr. Packard so it may really appear. To me it
seems that in the statement quoted, phrases of doubtful
meaning are being used in such a way as to vaguely assert
the opposite of one of the most obvious facts, namely, that
the first and second pairs of appendages of a King Crab are
far more like the first and second pairs of appendages of a
Seorpion than those of either are like the mandibles and
the maxille of hexapod insects.
Dr. Packard summarises his views as to Limulus and the
Crustacea thus: ‘‘ The facts that seem to us to point to the
Crustacean nature of Limulus and its allies are: (1) the
nature of the branchie, those of Limulus being developed in
numerous plates overlapping each other on the second ab-
dominal limbs; those of the Eurypterida being, according
to H. Woodward, attached side by side, like the teeth of a
rake ; while the mode of respiration is truly Crustacean ;
(2) the resemblance of the cephalothorax of Limulus to that
of Apus; (3) the general resemblance of the gnathopods to
638 PROFESSOR E, RAY LANKESTER.
the feet of the Nauplius or larva of Cirripedia and Copepoda ;
(4) the digestive tract is homologous throughout with that of
Crustacea, particularly the Decapoda, there being no urinary
tubes, asin Tracheata; (5) the heart is on the Crustacean
type as much as on the Tracheate type, and the internal
reproductive crgans (ovaries and testes) open externally, at
the base of and in the limbs, much as in Crustacea.”
To this series of statements I would reply categorically—
(1) the “nature of the branchie” is xo¢ such as is found in
any Crustacean, but is only paralleled in the lamelligerous
appendages of “Arachnida. Other animals have branchiz
besides Crustacea. The mode of respiration is neither truly
nor falsely Crustacean, but is simply ‘ branchial.’
(2) The cephalothorax of Limulus does noé resemble that
of Apus, but differs from it as much as it does from any
Arthropodous cephalothorax, as, for example, in the over-
lapping of posterior segments by the free posterior margin
of the carapace of Apus ; ; in the excavation of the carapace
in Apus by the shell-glands ; in the widely different position
of the first and second pair of appendages in relation to the
cephalothoracic margin ; in the total difference of the eyes ;
and, above all, in the totally different form, number, and
arrangement of the gnathites.
(3) The gnathopods have zo ‘‘ general resemblance to
the feet of the Nauplius” which calls for remark. They
have a general resemblance to the feet of any Arthropod,
but less to the feet of the Nauplius than to many other varie-
ties of Arthropod feet, owing to the fact that the former are
biramose, non- -chelate, natatory, and feebly chitinized, which
those of Limulus are not.
(4) The digestive tract is homologous throughout, not only
with that of Crustacea, but with that of all other Arthro-
pods. How Dr. Packard can suppose that itis homologous,
particularly with that of Decapoda, I am unable to compre-
hend, unless he proposed to himself, when writing this pas-
sage, to associate Limulus genealogically in a special branch
with the Decapoda. Unless this is the case Dr. Packard
makes use of the word ‘homologous’ with a meaning
which is unusual and unknown to me.
(5) That “ the heart is on the Crustacean type as much
as or the Tracheate type” I will not dispute, for I do not
feel sure that I know what Dr. Packard means, and he
appears to take up a neutral attitude, in regard to the heart
at any rate. I will, however, remark that, putting types
aside, there is no heart of a Crustacean which so closely re-
sembles the King Crab’s as does that of the Arachnid
LIMULUS AN ARACHNID, 639
Scorpion, and there is no heart which so closely resembles
the Scorpion’s as does that of the King Crab.
That the internal reproductive organs should open ex-
ternally in the neighbourhood of limbs is certainly not a
peculiarity of Crustacea. The relation of the openings to
limbs is not ‘much as in Crustacea,’ but quite unlike any-
thing seen in Crustacea. In no Crustacean does a pair
of limbs in front of the genital apertures unite to form
with a median lobe carrying those apertures—a broad plate,
as in the King Crab. A genital operculum of this nature
is found only in the King Crab, the Kurypterina, and the
Scorpion.
The extreme anterior position of the generative apertures
has no parallel among Crustacea nor among Arthropods,
excepting the Arachnida, where it is identical in position.
Even the chilognathous Myriapods do not exhibit so forward
a position of the genital orifices.
K. Conciusion ; LimuLus AND THE ANCESTRY OF
TRACHEATE ARTHROPODA.
The nature and degree of intimacy of the relationship
between Limulus and the Scorpion—which is indicated by
the facts and arguments set forth in the preceding essay—
have yet to be considered. It is one thing to establish the
fact that a closer relationship obtains between Limulus and
Scorpio than between Limulus and any Crustacean, and
another thing to estimate more precisely the affinity between
the two animals. :
A brief consideration of the facts is sufficient to show that
the points in which Limulus agrees with Scorpio and Mygale
include those structural features on which we have to rely
in attempting to characterise the class Arachnida. At the
same time it must be admitted that all attempts at limiting
classificatory groups by simple definition are hopeless, pro-
vided that the groups are intended to express degrees of
genealogical affinity, and not merely arbitrary categories,
held together by more or less obvious class marks. The real
question which we have to attempt to answer, in assigning
Limulus and the Arachnida their place in a genealogical clas-
sification of the Arthropoda is not, “ How may groups be de-
fined which shall give due expression to the structural
likenesses and unlikenesses of these forms ?” but, “‘ How may
groups be arranged so as to exhibit the probable history of
ancestral development in relation to these forms?” Owing
to the occurrence of degeneration, and to the suppression in
640 PROFESSOR E. RAY LANKESTER,
some forms of structural features which were the distin-
guishing characteristics of their immediate ancestry, we find
that frequently genealogical groups do not admit of strict
definition in terms of structure. And, further, we find that,
even in order to arrive at a clear notion with regard to the
relationships of a limited portion of a large group—such a
portion as are Arachnida in regard to the Arthropoda—it is
necessary to consider the genealogy of the whole series
included in the larger group.
The Arthropoda form a very large branch of a great
phylum to which I have applied the name ‘ Appendiculata’—
celomate animals with more or less distinct metameric seg-
mentation of the body and possessed of lateral lobes or
processes of the body itself which serve primarily as loco-
motor organs. Besides the Arthropoda the phylum Appen-
diculata includes the Rotifera and the Chetopoda. Each
of these three great branches of the Appendiculata has its
special developments, but it seems to be probable that they
all started from a common ancestry which had characters
intermediate to those of such a Rotifer as Pedalion and of
such a Chetopod as Syllis. Probably the Arthropoda were
developed from an ancestry resembling the Chetopoda, but
devoid of the chetz carried by the appendages of the
latter.
The distinguishing motive of the development of the
Arthropod branch of the Appendiculata is the adaptation of
one or more pairs of the appendages proper to the segments
succeeding the mouth, to the purposes of the prehension and
mastication of food. Hence it would be well to substitute
the term Gnathopoda for Arthropoda. All Arthropoda are
not arthropodous, that is to say, do not exhibit a jointing of
the exo-skeleton of the appendages. Peripatus though truly
a Gnathopod is not an Arthropod or Condylopod. The dis-
appearance of such jointing in connection with a softening
of the integument and a scavenger mode of life amongst
rotten wood, is one of those changes which it is probable
might occur as an adaptation, and accordingly it is very
doubtful whether we should regard the non-arthropodous
condition of Peripatus as a retention by it of the soft-bodied
character proper to the Chetopod-like ancestry of the
Arthropoda.
The structure of its eye, the presence of two lateral nerve-
cords in place of a double ventral cord, the limitation of the
jaw-feet to a single pair, the existence of paired nephridia
in each segment of the body, the peculiar histological struc,
ture of the muscular tissue,seem to me to be conclusive
LIMULUS AN ARACHNID, 641
evidence in favour of the view that Peripatus is a repre-
sentative of an exceedingly primitive grade of Arthropod
development, corresponding to a period when the Arthropod
branch had advanced but little on its special lines of differ-
entiation.
.At the same time Peripatus is specialised and adapted to
a terrestrial mode of life. It possesses no remnants of bran-
chial organs but a peculiar tracheal system, air being admitted
to the fine vessels formed by its vasifactive tissue through
irregularly scattered gland-like pits of the integument.
Its specialisation as a terrestical organism has, it is im-
possible to doubt, affected in Peripatus the locomotor appen-
dages also, so that much important information is wanting
to us, which, on the contrary, an aquatic form belonging to
the phase of development indicated by the eyes, nerve-cords,
nephridia, and gnathites of Peripatus, could have furnished.
It appears to me that we have no such aquatic represen-
tative form, and that Peripatus stands as a specialised ter-
restrial off-shoot at a much lower point in the Arthropod
family-tree than that at which we find outgrowths of exist-
ing branchiate Arthropoda.
The antenne of Peripatus probably are identical with the
similar organs of Chetopoda (cf. Spio and Phyllocheto-
pterus), and are zoé originally post-oral appendages which
have become preoral by adaptational shifting of the oral aper-
ture, but are actual lobes or processes of the primitive prosto-
mium, like the tentacles on the head of a snail, and inner-
vated by the archicerebrum or original prostomial ganglion.
In the interval between the giving off of Peripatus and
the production of the Phyllopod-lke ancestors of the Crus-
tacea from the aquatic Pro-Arthiopoda, a vast change had
to be effected in regard to appendages as well as in the
fusing of the nerve-cords, abolition of nephridia, produc-
tion of a compound eye, striation of muscular tissue, &c.
The prostomial antennz disappeared and their place was
taken first by one, then by two pairs of post-oral appendages,
which gradually acquired a pre-oral position as actually
occurs in their individual growth in the embryo at the
present day; eventually the simple prostomial ganglion
(archicerebrum) became complicated by the fusion with it
of ganglionic material proper to the two shifting appen-
dages, though in the existing Phyllopod Apus it still retains
its original purity and independence.
The other appendages probably all acquired at one stage
a development of their basal portion which served as an
accessory organ for the purpose of bringing food to the
642 PROFESSOR E. RAY LANKESTER,
mouth and in some degree in crushing such food (as seen
in Apus), but this development was specially carried out
and localised in two pairs of appendages posterior to the
one already so differentiated in Peripatus.
The segments, each with its pair of appendages, were
indefinite in number and frequently exceeded one hundred.
The definite Crustacean character was attained when two
pairs of appendages had become pre-oral, at least three
pairs specialised as jaws and no longer locomotor, whilst
the remaining appendages retained locomotor, manducatory,
and respiratory functions to be subsequently specialised in
the further development of the Crustacean stem.
It appears to me probable that the Merostomata, including
under this head the Xiphosura (Limulus), the Trilobita, and
the EKurypterina, diverged from the main stem! of the Arthro-
pod pedigree at a point between that indicated by the grade
of organisation of Peripatus and that occupied by the Pro-
Phyllopoda or earliest Crustaceans.
Probably none of the known Merostomata suffice to give
us a true picture of the structure of the ancestral Merosto-
mata from which they are all derived. Probably these
ancestral Merostomata were devoid of the prostomial an-
tenne—the non-appendicular antenne. At the same time
none of their post-oral appendages had become definitely
pree-oral in position and nerve supply, though not less and
probably not more than six pairs of pediform appendages
were closely set round the mouth, their bases acting as
powerful manducatory organs. To this group of appen-
dages, of which the corresponding segments were more or
less completely fused with the prostomium (forming the
prosoma), succeeded a mid-region of the body (the mesosoma),
consisting of numerous segments carrying biramose, pro-
bably pediform appendages, the bases of which were beset
with respiratory lamelle.
The generative apertures were situate in the first or one
of the anterior segments of this mid-region of the body.
A third region of the body (the metasoma), also consisting of
numerous segments, was probably distinguished by the form
and smaller size of its appendages and by a tendency of the
segments to fusion. Posteriorly to the anus was a median
plate or spine. Probably the eyes placed on the dorsal sur-
1 T have treated the line of descent leading to the Crustacea as the
main stem of the Arthropod family-tree; it is obviously a matter which
may be determined by convenience as to whether one or other of the
a ea of a genealogical tree shall be treated as the main line of the
family.
LIMULUS AN ARACENID. 645
face of the anterior region of the body were simple eyes,
but arranged in two lateral groups and a central group.
From such a form the Xiphosura were derived by reten-
tion of the full number of the appendages of the prosoma,
the limitation of the segments of the mesosoma to six, and
their specialisation as plate-like organs serving as genital
operculum, branchiz and swimmerets, further by the limi-
tation of the segments of the metasoma, first of all to six,
‘ and their subsequent fusion and partial disappearance even
from embryonic expression, and the atrophy of the append-
ages proper to them. At the same time the lateral groups
of simple eyes were replaced by a peculiar form of com-
pound eye.
The Kurypterina diverged from the Xiphosura after most
of these features had been elaborated, but so as to retain the
six free segments of the metasoma, whilst at the same time
they lost one pair (probably the most anterior) of the
appendages of the prosoma, and possibly the three hinder-
most of the appendages of the mesosoma.
The Trilobita diverged from the common ancestry of the
Xiphosura and Kurypterina probably at a time when the
number of six segments to the mesosoma and six to the
metasoma had not become a definite limitation, and when
appendages were carried by both those regions of the body,
differing only from the leg-like gnathites of the prosoma in
possessing a second ramus and lamelliform branchial pro-
cesses. Possibly the compound eye of the Trilobite was
inherited from an ancestor common to it and the Euryp-
terina. According to Walcot (12), a very distinctive feature
in the differentiation of the Trilobita was the reduction of
the number of appendages of the prosoma from six pairs to
four. In all these forms it is important to note that the
appendages of the prosoma, whether six pairs in number or
less, whether chelate, tactile, ambulatory, or natatory, so
far as the ‘ palp’ or chief ramus is concerned, yet all, with
the exception of the most anterior pair, continue by means
of their enlarged basal joint to act as manducatory organs.
As a set-off to the loss of the manducatory functions of their
coxe, the first pair possess, with rare exceptions, nipping or
stabbing palps.
The relationship of the Scorpion and other living Arach-
nida to the Merostomata appears to be this. From an
ancestral form, which was nearly related to the common
progenitor of the Xiphosura and Eurypterina, which pos-
sessed six pairs of appendages to its prosoma, the terga
united to form a carapace, six free segments to its meso-
644: PROFESSOR E. RAY LANKESTER,
soma and six free segments to its metasoma—the metasoma
devoid of appendages as in Xiphosura and Eurypterina, the
mesosoma provided with a genital operculum (united ap-
pendages) on its anterior segment and with five pairs of
lamelligerous respiratory appendages on the five succeeding
segments—from such a form by a very slight process of
change, consisting in adaptation to terrestrial in place of
aquatic conditions, the primitive Scorpions were developed.
It is probable that the particular form antecedent to the
differentiation of Xiphosura and Kurypterina, from which
the Scorpions took origin had not developed lateral com-
pound eyes, but still exhibited a primitive condition, which
is retained by the Scorpions and other Arachnida, viz. a
lateral grouping of simple eyes.
The structural changes necessary to produce a Scorpion
from such an ancestral Merostom as has been just sketched
are so small that it is not possible to place the Scorpions
and the Merostomata in separate classes, if by the use of the
division known as a ‘class’ we are to indicate as nearly as
possible, in different parts of the pedigree of animals, an
equal break or unrepresented interval of structural change.
At the same time the Scorpions, having once been developed,
appear to have given rise to the whole series of living Arach-
nida, to the Pedipalpi first, and through these to the
Araneina, and through the Araneina to the Acarina.
Galeodes is probably a special development from the
Scorpionina, as in a different direction are the Opilionina
and Pseudoscorpions.
This conclusion, if it be well founded, justifies some im-
portant inferences of a secondary character. In the first
place we have to admit a very extensive process of degenera-
tion in the course of development, leading from the Scorpion
to such Acarina as Demodex, or even Hydrachna. In the
second place we obtain a definite answer as to the mode of
origin of trachez, in so far, at least, as the trachez of the
Arachnida are concerned. The vascular lamelligerous
appendages of the Limuloid ancester of the Scorpion became
dry and filled with air in place of with blood. From this
blood-sinus, converted into an air-sinus, the air appears gra-
dually to have made its way, encroaching upon pre-existing
blood-canals, and converting them into air-canals. The highly
developed condition of the blood-vascular system in the
Scorpions renders it probable that the trachee of the tra-
cheate Arachnida are not mew vessels specially developed as
an aérial vascular system, but are the modified and adapted
blood-vascular channels, just in the same way as the air-
LIMULUS AN ARACHNID. 645
containing lamelligerous appendages of the Scorpion are not
new organs, but the modified and adapted blood-containing
appendages of a Limuloid ancestor.
The relationship of the groups of Arachnida to one
another thus suggested may be best indicated by means of
a genealogical tree (see last page). I have also drawn up the
names and arrangement of groups suggested in a tabular form.
I have further thrown into the form of a genealogical tree
the conclusions to which I am led in reference to the relation-
ship to one another of Peripatus, the Crustacea, and the
Arachnida.
In this pedigree of the Arthropoda no place is assigned to
the two great tracheate groups of Insecta Hexapoda and
Insecta Myriapoda. In the present state of knowledge it
appears to be impossible to assign to either of them one posi-
tion rather than another. We have not even sufficient
ground for concluding that they are closely related to one
another. The antennz of Hexapods and of Myriapods may
be, as probably are those of Peripatus, non-appendicular
prostomial antenne, which would be, in addition to the
presence of tracheze, a reason for considering both to have
been developed from such a form as Peripatus. On the
other hand, possibly only the Myriapoda are derived from
Peripatus-like ancestry, and, probably enough, neither
one nor the other. It seems to be in the highest degree
probable, and is not difficult of admission, that there is no
such a group to be recognised as the Tracheata. Trachez
have probably developed independently in Peripatus and in
the Insecta, and again in the Arachnida. Nevertheless, the
view is capable of being defended that all tracheate Arthro-
poda have a common tracheate ancestor ; in which case it
will be necessary to derive the Insects, the Myriapods, and,
to be consistent, Peripatus also, from the tracheate Arach-
nida, through such a form as Galeodes. The derivation of
Galeodes through the Scorpions, from the branchiate Arach-
nida, is, relatively speaking, a well-grounded conclusion ;
and if trachee are to have but one starting-point, it is of
necessity here that we must look for it.
Insuperable difficulties are, however, found in the deriva-
tion of Hexapoda from Galeodes, in spite of curious homo-
plastic agreements between the two. Such a difficulty is
the absence of appendages corresponding to the antenne of
Insects in Galeodes, and in the whole line of its Arachnidan
ancestry, which absence has to be recognised if the pincers
of Galeodes are identified with the mandibles of an Insect.’
1 I do not admit the truth of this identification.
VOL, XXI,—-NEW SER. UU
646 PROFESSOR E, RAY LANKESTER.
In deriving the Hexapods and Myriapods from Galeodes we
should have to suppose the antenne of the former to arise
de novo—a supposition which is contrary to one of the fun-
damental principles of phylogeny, viz. that new organs do
not arise de novo as new parts, but by the modification of
pre-existing parts.
Hence it seems that in any case the tracheate Arachnida
must be left apart from the other tracheate Arthropods as
the extreme modification of the series originating in the
Limuloids.
This conclusion is, however, in opposition to the view that
the renal Malpighian tubes are of phylogenetic significance.
It is a very striking fact that all well-developed tracheate
Arthropoda (except Peripatus) have not only trachee as
respiratory organs, but also have these Malpighian ceeca grow-
ing from the proctodeum. Either the Hexapods and Myria-
pods are closely related to the air-breathing Arachnids or
these Malphighan ceca have, like the trachez, appeared more
than once independently in divergent lines of the Arthropod
family-tree.
A minute comparative study of the structure and devyelop-
ment of these ceca is wanting; at the same time it appears
that certain of the Isopod Crustacea possess organs com-
parable to them. If this be so, another possible place of
attachment for the Hexapods and Myriapods to the Arthro-
pod family-tree is indicated, which, on independent grounds,
has much in its favour. Supposing that the antenne of
Hexapods and Myriapods should prove not to be identical
with the prostomial antenne of Cheetopods but should be
shown by the examination of the development and structure
of their connected nerve-ganglia to be like those of Crus-
tacea, originally post-oral appendages, or supposing on any
other grounds that the antenne of these forms could be
identified with one pair of the Crustacean’s antenne, then
it would not be difficult to conceive of such a modification of
the post-oral appendages of an Isopod as would give the
disposition characteristic of them in either Myriapods or
Hexapods.
And it is to be noted that among existing Isopods, terres-
trial forms are known with peculiar lung-like pouches
adapted to aérial respiration.
A strong argument in favour of the derivation of the Hexa-
poda from Crustacea appears at first sight to be afforded by
the minute structure of the compound eye of the two series
of organisms.
Amongst all the possible points of genetic connection of
LIMULUS AN ARACHNID. 647
the Hexapoda and of the Myriapoda with the other large
groups of Arthropoda, there is probably more hope of a
definite indication being obtained as the result of a critical
study and comparison of the structure of the eyes than
from any other source. The eyes of Arthropods are elaborate
in the histological details of their structure, and at the same
time have not been inherited from a common ancestor in one
and the same elaborate form by all the members of the group, as
have been the eyes of craniate Vertebrata for example. Ac-
cordingly we may expect that the elaboration of the eye has
taken a somewhat different course in different lines of descent
within the limits of the Arthropod phylum, and we should
be justified in concluding a common line of descent for
classes of Arthropods showing identity in numerous details
of the optical structure, which details had been ascertained
not to be acommon inheritance from the primeval Arthropod
ancestor.
Whatever may be the conclusion arrived at in the future
in reference to the affinities of Hexapoda and Myriapoda,
the result of the recognition of the intimate relationship of
Scorpio and Limulus must be, I think, to break up the
artificial group of ‘* Arthropoda Tracheata ” by the separation
of the Scorpions, Spiders, and Mites, from any special con-
nection with it.
Phylum.—APvPEnDICcULATA.
Branch 3.—Arthropoda (Gnathopoda).
Class.—Arachnida.
Arthropoda developed from ancestral forms, in which a
‘ prosoma’ formed by the union of the prostomium and six
anterior segments was sharply marked off from the rest of
the body, both by the confluence of its terga to form a
carapace and by the special character and size of its appen-
dages. ‘The six pairs of appendages (including the foremost
of the whole series) were arranged round the mouth, and all
subservient to the purpose of prehension and mastication of
food. In the later developed forms of Arachnida either
the number of these appendages may be reduced (Euryp-
terina, Trilobita), or the functional relation to the mouth of
the more posterior of the six pairs may be lost. Whatever
their number, the foremost pair is free from a jaw-like
enlargement of the coxa. The palps of all six pairs of
appendages exhibit a wide range of adaptational form, as
prehensile, tactile, ambulatory, natatory, or fossorial organs.
648 PROFESSOR E, RAY LANKESTER.
The generative apertures are placed far forward—ances-
trallyin the first segment of the ‘mesosoma’ or region following
the prosoma, and are covered by a fused pair of appendages,
or, when these have aborted, by the corresponding sternite.
The appendages of the mesosoma posterior to the
generative apertures carry peculiar respiratory lamelle,
which expose the blood circulating in them to the dis-
solved oxygen of natural waters in the more archaic
members of the group, but are perforated, invaginated in
recesses of the ventral integument, and filled with atmos-
pheric air in terrestrial forms (Scorpions, Spiders, &c.), or
may be altogether aborted and replaced by trachee.
Except in the Trilobita the segments and paired appendages
of the mesosoma are not more than six in number, and the
same is true of the metasoma or terminal region of the body,
which is devoid of appendages (except in Trilobita), and
may either have the appearance of a simple continuation of
the mesosoma (macrourous forms), or may have its seg-
ments fused with one another, but separate from those of
the mesosoma (Trilobita) ; or, again, may be more or less
completely aborted and fused with the mesosoma (Limulus),
when the segmentation of the mesosoma itself may also
become partially (Spiders) or completely (Acarina) oblite-
erated.
In all the larger known forms (Limulus, Scorpio, Mygale)
a large free sclerite, the entosternite, is found within the
prosoma, giving attachment to muscles inserted into the
sternites of the mesosoma.
Tabular view of the Orders of Arachnida.
GraDE A.—H#MATOBRANCHIA (= MeRosTOMATA) :
Orderl . f : ; : Trilobita.
Ph Dae : : : : Eurypterina.
Bi Aa : y ; : Xiphosura.
GraDE B.—ABROBRANCHIA :
Orderl . : : ; 3 Scorpionina.
Ren D> th, ; : : : Pedipalpi.
iS BD ves : : ? , Araneina.
GRADE C.—LIPOBRANCHIA :
Otter. *. . : : Solifuge.
eee. : : f ; Pseudoscorpionina.
ue. ; 5 : ; Opilionina.
eae. ; : ; ; Acarina.
649
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NOTES AND MEMORANDA.
Dr. Koch’s New Method of Pure Cultivation of Bacteria.—At
the recent meeting of the International Medical. Congress in
London, during August, Dr. Koch, well known by his
researches on the life-history of Bacillus anthracis (see this
Journal, Vol. XVII, p. 87), gave a series of demonstrations
in the physiological laboratory of King’s College, which
were of the greatest interest and importance.
Dr. Koch has recently been appointed to the charge of a
laboratory of experimental research connected with the State
Department of Public Health in Berlin, and aided by his
two assistants, he brought to London material and instru-
ments for the purpose of exhibiting to the members of the
Congress the methods of research into the relation of Bac-
teria to disease, devised by him. The series of photographs
of various forms of Bacteria shown by Dr. Koch were valu-
able, as affording convincing evidence of the necessity of
making use of photography as the means of obtaining and
preserving a record of the specific form and character of
Bacterian growths. Of great interest also were the cultiva-
tions of the Bacteria of blue milk, and of those of blue pus,
exhibited by Dr. Koch, and of the septic Bacterium of
putrid blood, the toxic effects of which were experimentally
demonstrated.
Of most general importance, and in our judgment likely
to mark altogether a new era in the study of the relations
of Bacteria to certain diseases, and to other fermentative
processes, was the demonstration by Dr. Koch of a new
and yet absolutely simple and obvious method of obtaining
pure cultivations of the species of Bacteria.
It is a well-known fact that there are a large number of
species of Bacteria differing from one another in the effects
which they produce in the medium wherein they are culti-
vated. It is also well known that Bacteria are so ubiqui-
tous that the examination of any natural medium attacked
NOTES AND MEMORANDA. 651
by them is almost sure to yield evidence of the presence of
more than one species, the various species growing together
in inextricable confusion. On this account it has been
found a matter of extreme difficulty to determine what
effects are due to one species of Bacterium and what to
another. And it has indeed been often impossible to deter-
mine in such a mixture of forms those which are genetically
related to one another, and therefore to distinguish one
species from the other forms which are adventitiously asso-
ciated with it.
To effect the separation of species in a mixture, Mr.
Lister employed a method of dilution and division des-
cribed in his well-known research on the Lactic ferment
(see this Journal, vol. xviii, p. 191). Making use of a fluid
as the nutrient medium of cultivation (as hitherto has been
the almost universal practice in such cultivations), Mr. Lister
introduced a drop of sour milk containing possibly twenty
kinds of Bacteria, and among them the Bacterium of lactic
fermentation, into a large quantity of pure water, the dilution
and spacing (so to speak) of the Bacteria thus affected being
calculated so to render it probable that a séngle drop removed
from the diluted Bacterian mixture would contain a single
Bacterium. Such drops were then removed and placed each
into a separate culture-tube containing sterilized fluid nutri-
ment, and thus in a certain number of the tubes a pure cul-
tivation consisting of the progeny of a single Bacterium,
and, therefore, unquestionably of but one species, was
obtained.
This method is tedious and liable to failure owing to the
great care necessary to ensure and maintain sterilization of
the cultivation fluid whilst exposed for the purpose of inocu-
lation and again for further examination. Dr. Koch was
led to this new method of cultivation, which essentially con-
sists in the substitution of a solid for a fluid medium of
cultivation, by the use of the method! known to all my-
cologists of cultivation, upon slices of potato or beet-root.
It is readily observed when slices of boiled potato are ex-
posed in a damp condition to the atmosphere that the sur-
face of the slice becomes the seat of development of various
Bacteria and of moulds, the spores of which fall from the
atmosphere on to the exposed slice, a fact which struck Dr.
Koch as of importance in reference to the slices of potato
was this—that the various spores falling on to it remain
where they fall, and from the spot where each spore or germ
originally fell it proceeds to multiply, producing around it a
symmetrical hemispherical growth of perfect purity. In fact,
652 NOTES AND MEMORANDA.
owing to the solid character of the nourishing support the
germs and spores cannot get mixed as they do in a liquid,
each remains distinct from its neighbour even though in very
close proximity, and without any trouble from the resulting
growth, which proceeds in a day or two from each germ—
new and perfectly pure cultivations may be started in suitable
sterilized fluids.
Dr. Koch’s method consists in substituting for the potato
slice a layer of gelatine which is so saturated with water as
just to become solid on cooling. The gelatine liquid is
readily sterilized by boiling, and into it can be introduced
either Pasteur’s salts, peptones, blood-serum, or other nu-
trient material required by one or other species of Bac-
terium. The gelatine-medium thus prepared may be kept
in atube and a cultivation thus carried on—on its sur-
face, or (and this is its principal use) it may be spread when
liquid on a microscope object-slide and allowed to cool. Then
such a gelatine plate may be inoculated by touching its
surface with material containing the Bacteria which it is
desired to study. The plate is readily protected from the
access of accidental atmospheric germs, and maintained at
such temperature and degree of moisture (by a glass shade)
as the experimenter may desire. The main point of advan-
tage, however, is this—that the point of inoculation on the
surface of the gelatine can, owing to its transparency, be
readily examined with the highest powers of the microscope
and the growth of the Bacteria followed—whilst further,
owing to the fact that the medium in which the growth
takes place is solid, no mixture of the different kinds which
may be present occurs, but each Bacterium produces around
it a little spherical nest of itsown kind. From these nests,
with a sterilized needle-point, individuals can be removed to
start new pure cultivations.
But it is obvious that, if the original point of inoculation
was very minute, there is no danger of any accidental con-
tamination from atmospheric germs, for these are not likely
to fall on the identical spot no bigger than the puncture of
a needle’s point, where the experimental culture is going
on. As a matter of fact, where they fall on to the gelatine
there they remain and grow, and fifty such accidental
spores may fall on to the gelatine plate without in the least
interfering with the purity of the experimental culture.
There is yet, further, a very simple device which enables
Dr. Koch to use this gelatine surface as a means of
“spacing” and dividing the various species in a mixture of
Bacteria, He dips a sterilized needle into such a mixture,
NOTES AND MEMORANDA, 653
and then makes a long shallow streak with the needle’s
point upon the surface of the gelatine. The Bacteria which
were adhering to the needle’s point are in this way dropped
at intervals along the streak, some nearer some further
apart, but all (with rare exceptions) in such a way that
their subsequent growth keeps clear of that of a neighbour,
and can, with the aid of a low power or even without any
microscope, be visited by a sterilized needle point, and thus
used to start on another gelatine plate a perfectly pure cul-
tivation.
These pure cultivations, such as Lister aimed at by his
method of dilution and division, may be called, in order to
indicate to what an extent they are known to be pure,
*‘monosporous cultivations,” since the principle which dis-
tinguishes them is that all the growth is the offspring of a
single isolated germ or spore.
It is only by such monosporous cultivations that we can
arrive at solid conclusions in reference to the forms and
activities of the Bacteria, e.g. as to whether one form can
give rise to progeny of another form when its food and con-
ditions of growth are changed, and again, as to whether
special fermentative powers can be lost or acquired in the
course of generations derived from one parent germ, but
subjected to different conditions as to food, temperature, and
oxygen.
The method of gelatine cultivation devised by Dr. Koch,
places the means of following out these inquiries in the
hands of every careful microscopist. Such methods as
Lister’s were too troublesome and too difficult for general
and widespread application; but now that monosporous
cultivation of Bacteria has been rendered a comparatively
simple and certain affair, we may expect immediate and
immense advances in our knowledge of the whole series
of phenomena to which the Bacteria are related.
Amongst problems which require immediate investigation
by the new method are the distinctive properties of the various
kinds of Bacteria which may infest the wounds of surgical
practice, and their specific susceptibility to the destructive
influence of carbolic acid and other antiseptics ; further, the
possibility of isolating a specific Bacterium in contagious
diseases not yet investigated: and (of great physiological
interest) the isolation and investigation of the properties
of the specific Bacterium of the ammoniacal fermentation of
urine.
Dr. Koch and his assistants will, no doubt, shortly publish
a detailed account of the researches which they have been
654 NOTES AND MEMORANDA,
engaged in during the past year, and will give particulars
as to the methods of investigation employed by them, which
had not (we believe), previously to the meeting of the
International Medical Congress, been given to the public.
A remarkable negative result obtained by Dr. Koch, so
far as his experiments with the new method of monosporous
culture have yet extended, is, that there is no transition of
forms amongst, at any rate, the pathogenous Bacteria—a
Micrococcus produces Micrococci, and no other form; a
Bacillus produces only Bacilli; a biscuit-shaped form (Bac-
terlum proper) only biscuit-shaped forms; a Spirillum only
Spirilla. Moreover, the facies of the discoidal or spherical
mass formed by a growth, as seen with a low power excavat-
ing its way in the gelatine is characteristic of species, so that
a practised observer can, in some cases, recognise a particular
Bacillus or Micrococcus by the naked-eye appearance of the
growth alone, or, at any rate, without actually observing the
individual units of the growth.—L.
INDEX TO JOURNAL.
VOL. XXI, NEW SERIES.
Actinotrocha, metamorphosis of, by
E. B. Wilson, 202
Apus cancriformis, appendages and
nervous system of, by E. Ray
Lankester, 343
Bacteria, Koch’s new method of pure
cultivation of, 650
Bennett, A, W., on the terminology
of the reproductive organs of Thal-
lophytes, 165
Blomfield and Bourne on corpuscles
in the red vascular fluid of Chesto-
pods, 500
Blomfield, on development of the
Spermatozoa in Helix and Rana,415
Blood-corpuscles, micrometric enu-
meration of, and estimation of
‘Hemoglobin, by Mrs. Ernest Hart,
132
Blood-corpuscles of man and other
vertebrata, by G. F, Dowdeswell,
154
Bourne and Blomfield on corpuscles
in the red vascular fluid of Cheto-
pods, 500
Bower, on Welwitschia, 1, 571
Brady on Reticularian Rhizopoda, 31
Busk, on a peculiar form of Polyzoa
allied to Bugula (Kinetoskias), 1
Carpenter, P. Herbert, on the minute
anatomy of the brachiate Echino-
derms, 169
Cheetopods, corpuscles in the red vas-
cular fluid of, by Blomfield and
Bourne, 500
Chick, Wolffian duct and body in, by
Adam Sedgwick, 432
Claus on intracellular digestion in
Hydrozoa, 377
Corpuscles in the red vascular fluid
of Chetopods, by Blomfield and
Bourne, 500
Cunningham, D. D., on the develop-
ment of certain microscopic or-
ganisms occurring in the intestinal
canal, 234
Dowdeswell on some appearances of
the red blood-corpuscles of man
and other vertebrata, 154
Echinoderms, minute anatomy of the ©
brachiate, by P. Herbert Carpenter,
169 re
Elasmobranchs, head-cavities and° as-
sociated nerves of, by A. Milnes
Marshall, 72
Excretory system in vertebrata, Sedg-
wick on, 432
Gardiner, W., on water-glands in the
leaf of Saxifraga crustata, 407
Geryonia and Limnocodium, young ~
stages of, by EH. Ray Lankester, 194:
Gills, aberrant forms of Lamellibranch, _
by K. Mitsukuri, 595
656
Guinea-pig, organ of Jacobson in, by
E. Klein, 219
Hemoglobin, estimation of, by Mrs.
Ernest Hart, 132
Harris, Vincent, on Pacinian corpus-
cles in the pancreas and mesenteric
glands of the cat, 502
Hart, Mrs. Ernest, on the micrometric
enumeration of blood-corpuscles
and the estimation of their Hiemo-
globin, 132
Haycraft, J. B., on cause of striation
of muscular tissue, 307
Helix, spermatozoa of, 415
Histological notes, by E. Klein, 114,
231
Intestinal canal, microscopic organisms
in, by D. D. Cunningham, 234
Intra-cellular digestion in Hydrozoa,
Claus on, 377
Intra-cellular digestion of Limnoco-
dium, E. Ray Lankester on, 119
Jacobson, organ of, in the guinea-pig,
by E. Klein, 219
5 oa in the rabbit, by
KE, Klein, 549
Kent, a manual of the Infusoria, 377
Kinetoskias, by George Busk, 1
Klein, E., histological notes, 114, 231
» on minute anatomy of the
nasal mucous membrane, 114
a on the lymphatic system of
the skin and mucous membranes,
379
59 on the minute anatomy of
the organ of Jacobson in the guinea-
pig, 219
is on the organ of Jacobson
in the rabbit, 549
Koch, new method of pure cultivation
of Bacteria, 650
Lamellibranch gills, aberrant forms of,
by K. Mitsukuri, 595
INDEX.
Lampreys, development of, by W. B.
Scott, 146
Lankester, E. Ray, on intra-cellular
digestion and endoderm of Limno-
codium, 119
4 < on Limulus, 504,
609
ay A on the appendages
and nervous system of Apus can-
criformis, 343
“ S on young stages
of Limnocodium and Geryonia, 194.
Limnocodium and Geryonia, young
stages of, by E. Ray Lankester, 194
Limnocodium, intra-cellular digestion
and endoderm of, by HE. Ray Lan-
kester, 119
Limulus an Arachnid, by E. Ray
Lankester, 504, 609
Lister, Joseph, on relation of micro-
organisms to disease, 330
Lymphatic system of the skin and
mucous membranes, by E. Klein,
379
Marshall, A. Milnes, on the head.
cavities and associated nerves of
Elasmobranchs, 72
Marshall and Spencer on cranial nerves
of Scyllium, 469
Medusz living in fresh-water, Ro-
manes on, 162
Micrometric numeration of blood-
corpuscles, by Mrs. Ernest Hart,
132
Micro-organisms, relation of, to dis-
ease, by Joseph Lister, 330
Mitsukuri, on aberrant forms of La-
mellibranch gills, 595
Mucous membranes, lymphatics of, by
Klein, 379
Muscular tissue, cause of striation of,
by John Berry Haycraft, 307
Nasal mucous membrane, minute
anatomy of, by H, Klein, 114.
INDEX.
Nerves and head-cavities of Elasmo-
branchs, by A. Milnes Marshall, 72
Nerves, cranial, of Scyllium, by A.
Milnes Marshall and W. B. Spen-
cer, 469
Pacinian corpuscles in the pancreas
and mesenteric glands of the cat,
by Vincent Harris, 502
Polyzoa, on a peculiar form of, by
George Busk, 1
Rabbit, organ of Jacobson in the, by
E. Klein, 549
Rana, spermatozoa of, 415
Reticularian Rhizopoda, Brady on, 31
Romanes, G. J., on Meduse living in
fresh water, 162
Saxifraga crustata, water-glands in the
leaf of, by W. Gardiner, 407
Schimper, F. W., on starch-grains,
291
Scott, W. B., preliminary account of
the development of the Lampreys,
146
Scyllium, cranial nerves of, by A. M.
Marshall and W. B. Spencer, 469
657
Sedgwick, Adam, on the early develop-
ment of the anterior part of the
Wolffian duct and body in the chick,
together with some remarks on the
excretory system of the Vertebrata,
432
Skin, lymphatic system of, by Klein,
379
Spencer and Marshall on cranial nerves
of Scyllium, 469
Spermatozoa, development of, in Helix
and Rana, by J. E. Blomfield, 415
Starch-grains, development of, by F.
W. Schimper, 291
Thallophytes, terminology of, by A.
W. Bennett, 165
Water-glands in leaf of Saxifraga
crustata, by W. Gardiner, 407
Welwitschia, by F. Orpen Bower, 1,
571
Wilson, E. B., on the metamorphosis
of Actinotrocha, 202
Wolffian duct and body in the chick,
by Adam Sedgwick, 432
PRINTED BY J. E. ADLARD, BARTHOLOMEW CLOSE.
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