ON THE 
ANATOMY AND HISTOLOGY 
OF 
F 
Cymbuliopsis Calceola 
BY 
J. I. 
Reprinted from " Studies from the Biological Laboratory, Johns Hopkins University,' 
Vol. IV., No. 6. 
BALTIMORE : 
PRESS OF ISAAC FRIEDENWALD, 
32 S. Paca Street. ON THE ANATOMY AND HISTOLOGY OF CYM- 
BULIOPSIS CALCEOLA. By J. I. PECK. With 
Plates XXXVI-XXXIX. 
The specimens upon which the following researches were 
made were collected in the Gulf Stream, off Cape Charles, in 
October, 1888, by the Fish Commission schooner Grampus, and 
my thanks are due to the U. S. Fish Commissioner Prof. M. 
McDonald for affording me the opportunity to make the expedi- 
tion, and also for putting the vessel and her crew at my service 
during the cruise. 
It is the purpose of the present paper to give the anatomy of 
the pteropod Cymbuliopsis calceola, as obtained from a study of 
serial sections of the entire animal; also to indicate the histolo- 
gical elements of some of the principal tissues as they appear in 
their anatomical connection. The molluscs were taken at the 
surface of a moderately rough sea, at lat. 37° 11' N., long. 74° 
15' W., in an early morning at the beginning of October, 1888. 
The specimens were killed in Perenyi's fluid and hardened in 
alcohol, by which process the tissues generally were well pre- 
served, with some shrinking of the delicate connective tissue 
network, however, in the process of imbedding. A successful 
double-staining in toto was realized with dilute Kleinenberg's 
haematoxylin, followed by borax carmine. 
The systematic position of the pteropod has been given by the 
new classification of the family Cymbuliidae as proposed by 
Pelseneer,1 according to whom the new genus Cymbuliopsis is 
established, to include two species, which are distinct from 
Cymbulia on the one hand in having no "ventral lobe of the 
foot," nor " lash-like appendage " below the fin, also in having 
the flattened proboscis free from the upper surface of the base of 
the fin, and differing especially in the shape of the " slipper " or 
1 Report on the Pteropoda collected by H. M. S. Challenger during the years 
1873-1876, Part LXV, p. 96. 2 
J. I. PECK. 
" shell," which in Cymbulia is pointed at the aboral end and 
truncated at the anterior end, with long pointed tubercles along 
the margin. The genus also differs on the other hand from 
Gleba (Tiedmannia), inasmuch as the latter has a "shell" with a 
much more widely open cavity. The true shell, with operculum, 
of these forms, however, the homologue of the ordinary molluscan 
structure, only exists during larval stages,1 having nothing in 
common with this secondary thickening of the mantle of the 
adult Cymbuliidae. I have therefore, referring to its present 
protective nature as a thick leathery armor into which the body 
of the animal slips as a helmet encloses the head, called this 
later structure in Cymbuliopsis-formed within the mantle- 
the casque, distinguishing it from the true shell of the mollusc, 
which was doubtless present in larval life. 
The general form of the pteropod from a dorsal view is shown 
in Pl. XXXVI, Fig. 1, and that of the casque in Fig. 2, both 
drawn from a specimen in alcohol, in which the casque has 
slipped out of the mantle in which it was secreted, leaving the 
frayed portions of the exterior layer of the same still hanging 
from the body of the animal. The wide flattened proboscis,p, 
-the head region-is in contact with, yet free from, the upper 
surface of the fin. It is in fact in this case asymmetrical in form ; 
a result perhaps of its shrinking in alcohol. Its edges are rolled 
outward to form a ciliated groove, which is, no doubt, sensory 
in function. Directly at the front part of the proboscis is the 
mouth, a large distensible opening regulated by loose lip-like 
folds. The position of the rudimentary tentacles-one upon 
either side of a median line over the oesophagus-is shown at t, 
and they are ordinarily discernible in surface views, although 
they are not shown in the figure. They are sometimes wholly 
absent, for in a very complete series of sections of one specimen 
they do not appear, while in another series they are -well defined 
through at least ten sections, having a retractor muscle under- 
neath and a nerve supply. But at best the tentacles are mere 
knob-like structures, with rudimentary sensory structure at their 
base, however, and they may be retracted to the general surface 
level of the proboscis. The oesophagus leads backward and 
' See Klassen und Ordnungen des Thierreichs, Bronn und Keferstein-Mala- 
cozoa, pp. 630-632. CYMBULIOPSIS CALC EOLA. 
3 
downward to the visceral mass or nucleus, seen through below 
and displaced to the left. All the tissues of the animal are 
exceedingly translucent, so that the course of the oesophagus 
may be followed from surface view. In perfect specimens 
the visceral nucleus is still enclosed in the pallial cavity by 
the internal layer of the mantle, represented in the figure by 
a circle drawn a little way exterior to the visceral nucleus, 
but this latter is generally more or less torn in the loss of 
the casque at the capture of the animal. This dark-brown 
rounded "nucleus" contains the digestive and reproductive 
organs, and on its dorsal surface the heart and nephridium are 
laid. The primitive molluscan foot cannot be recognized in the 
adult animal, while its successor, the fin, has attained very large 
relative proportions, and is moved by muscles which are laid 
in regular intercrossing bands a little beneath the epithe- 
lial surface of either side, both dorsal and ventral alike; the 
thickness of the fin being made by the branching network of 
connective tissue cells so characteristic of molluscan histology. 
The structure and disposition of these muscle bands has been 
recently described for other pteropods by Paneth,1 and in com- 
parison with the heteropods by Kalide,2 but without especial 
reference to Cymbuliopsis. In the latter genus there are three 
definite layers of bands controlling the fin, Fig. 1, i, 2 and s. 
Of these the most exterior bands are (1) the narrowest, and are 
distributed nearly parallel to each other over the whole surface 
of the fin in an antero-posterior direction. These lie directly 
upon and across the next layer beneath them (2), which is made 
up of thicker and much broader bands running across the fin 
from one side to the other in arcs of circles. And finally the 
innermost bundles (3) are distributed radially from beneath the 
proboscis in such a way that the two lateral portions of the fin 
are supplied by them, a few bands a little to the right and left of 
the median line in front of the proboscis being omitted. All 
the muscle bands as they near the edge of the fin become small 
and branch out to anastomose with each other. The edge 
1 Beitrdge zur Histologie der Pteropoden und Heteropoden, Archiv fur mik. 
Anat., Bd. XXIV, pp. 235, 262. 
2 Beitrag zur Kentniss der Jlfuskulatur der Heteropoden und Pteropoden, 
Zeit. fur Wiss. Zodl., Bd. XLVI. 4 
J. I. PECK. 
of the fin also contains branched connective tissue cells and 
processes passing from a central cell nucleus to both surfaces. In 
the general interior of the fin, of course, is the network of con- 
nective tissue cell processes, and the branching nerve trunks and 
blood lacunae. The mollusc also possesses six longitudinally 
laid muscle bands on the dorsal surface of the proboscis. The 
relations of the parts in place from a ventral view are shown in 
Fig. 3. The visceral nucleus, from this view quite surrounded 
by the pallial cavity k (bounded by the circumscribing line in 
the diagram), shows at its aboral end, at 2, a peculiar darkly 
pigmented ring, which is superficially placed and presents differ- 
ences in size in different specimens; when the circumference of 
the ring is large the wall is low, and when contracted it is more 
prominent and stands out more upon the visceral mass. This 
limiting wall is made up of the characteristic branched cells, 
with single and branched muscle fibres (Fig. 27, cut at 
different angles, and it carries on the inside a layer of columnar 
cells which are much elongated in the bend. Pelseneer1 has 
also mentioned this structure, and as being like a sucker in 
form. In Fig. 27, Pl. XXXIX, is represented a vertical section 
through one side of the ring in a specimen where it is much 
contracted. The pigment is distributed in the protoplasm of the 
columnar cells, whose nuclei are also a dark brown. 
The pallial cavity of Cymbuliopsis is on the ventral side, and 
is made by the large fold of the mantle which extends from the 
dorsal part of the animal around beneath the fin, thickening 
between its two epithelial layers into the hyaline casque. (This 
latter appears in sections to be deposited in irregular layers, as 
it stains with difficulty except in streaks, and shows granules 
which are doubtless deposits of inorganic salts; it does not con- 
tain cells.) Part of the inner layer of the mantle is specialized 
into the " pallial gland," or " shield " of thecosomatous pteropods. 
The position of this-seen through from the exterior-is shown 
in Fig. g. It is almost symmetrical in this genus, being 
twisted somewhat to the right, but the asymmetry is not marked, 
and it is crossed by two transverse bands-an anterior small one 
and a broader posterior one-somewhat faintly shown in the 
figure, also one passing along the edges of the structure a part 
1 Challenger Reports, Part LXVI, p. 27. CYMBULIOPSIS CALCEOLA. 
5 
of the way. Sections through this " shield " show that the cells 
which compose the different areas are quite different in their 
appearance. Thus in Pl. XXXIX, Fig. 26 shows in section 
the long club-shaped cells £, which cover the general surface of 
the pallial gland on the side toward the cavity, and stain very 
deeply, while the transverse bands are made up of the cells -w, 
which stain more lightly, and are regularly arranged so as to 
give the surface an undulatory contour. The outer portion of 
these closely packed cells v is clear, and between the larger cells, 
near the surface, are found certain smaller nuclei n. The transi- 
tion between the two areas is very abrupt, and the function of 
the two, whatever it may be, is doubtless as distinct. Behind 
the pallial gland, which thus forms a widely open pocket, the 
general pallial cavity is much narrowed down, opening into 
that part which surrounds the visceral mass by a transverse 
crescentic slit (below k, Fig. 3;-at y, Fig. 4). This posterior 
part of the cavity contains the visceral nucleus suspended in it, 
but it is asymmetrical in extent on account of the presence of 
the large nephridium, which extends farther down upon the left 
side, so that the pallial cavity extends farther dorsalwards on 
the right side than on the left, while behind it extends quite up 
on to the dorsal side as far as the large nephridium. Thus in 
Fig. 4 are shown the relations of the parts in diagram from the 
right side; m the mouth at the proboscis, t the rudimentary 
tentacles, n the central nerve ganglia, k the casque contained in 
the mantle, j the nephridium with the heart in front of it, y the 
opening from the larger exterior part of the pallial cavity with 
its pallial gland p. g. into the interior part of the same, where 
open the anus and the genital ducts at w. The external features 
of the mollusc, the extent of the mantle, pallial cavity and 
shield, the position of the visceral organs, the fin and its muscu- 
lature have thus been indicated in Pl. XXXVI, Figs. 1-4; the 
structure of the shield and dark ring or sucker in Pl. XXXIX, 
Figs. 26 and 27. 
In order to show the arrangement of the organs of the visceral 
mass I have figured on Pl. XXXVII (Figs. 8, 9 and 10) three 
representative cross-sections at different points through the body 
of the animal. The outlines of the visceral organs were made 
with the camera lucida, while the outer epithelium (k) of the 6 
J. L PECK. 
mantle and the inner layer (w) of the same, and the intervening 
thickening-the casque-are represented diagramatically in 
place. Fig. 8 is the most posterior section, the pallial cavity 
quite surrounds the visceral mass, the nephridium n is just cut 
on the dorsal side as a double cavity at this point. The intes- 
tine of Cymbuliopsis, after leaving the stomach, makes a single 
loop around the visceral nucleus (Fig. 4, i) under the genital 
gland, and opens a little to the right of the median line; and 
here, in Fig. 8, is cut so that the coil is just disappearing at i on 
the left, while the part of the intestine leading directly to the 
anal opening is cut at i on the right. The beginning of the 
enlargement of the stomach s is on the dorsal side, and opens 
widely into the liver Z, the opening being to the right of a median 
line. The liver Z is quite internal then, and the gland is made 
up of loose lobules. The genital gland h is most exterior, and 
envelops the liver and intestine. In Fig. 9, farther forward, 
about the middle of the visceral nucleus, the nephridium is cut 
in two parts, right and left, r. n and Z. n, while between them 
appears an irregular part of the pericardial cavity p. c, in which 
the ventricle would appear more anteriorly. This section passes 
about through the centre of the stomach s, with the five thick- 
ened plates upon its walls. A very large blood sinus ao passes 
below the stomach into the tissues of the liver Z, which, with the 
genital gland A, occupies the same relative position as in the 
other figure. At a is seen the terminal portion of the anal 
opening into the pallial cavity, a little to the right of the median 
line ; although in surface views it is seen to be directed toward 
the left, yet it does not reach the median vertical line. The 
pallial cavity itself in this, as in the following sections, is seen 
to extend farther dorsalwards on the right side than on the left. 
Fig. 10 is taken far enough forward to pass through the ventricle 
v, just before its union with the posterior blood-vessel ao\ 
the nephridium, r. n and Z. n, has almost disappeared on either 
side, while the pericardial cavity pc is becoming more apparent, 
and would steadily increase in the more anterior sections of the 
series until it is limited by the general connective-tissue filled 
space of the body cavity. The stomach s is cut through its 
anterior end, where only two of the thickened plates are devel- 
oped ; the liver has almost disappeared, and the genital gland A CYMB ULIOPSIS CALC EOLA. 
7 
is divided into two lateral portions by the ventral position of the 
accessory glands and the genital ducts, to be described hereafter. 
In following serial sections farther forward, the liver and the 
genitalia run out, the stomach runs into the oesophagus, the heart 
gives off the large aorta, the mantle shows the specialized pallial 
gland, the nerve ganglia appear around the oesophagus, and 
the general tissues of the fin and proboscis appear. 
The Digestive Organs. 
The general position of these has already been described; 
beginning'with a large, loose mouth at the proboscis, from 
which the long oesophagus leads backward into the stomach, the 
thickened walls of which bear the triturating plates. At the 
extreme posterior end of the stomach, at the beginning of the 
intestine occurs the wide asymmetrical opening into the " liver " 
(Fig. 8), 'while the intestine itself takes one bend downward and 
around over on to the right side and beneath, where it opens 
nearly upon the median line, although plainly to the right of it, 
which is contrary to the position described for the other Cymbu- 
liidae. Its latter portion is directed toward the left, as it opens 
into the pallial cavity. Cymbuliopsis has no buccal armature nor 
salivary glands; the oesophagus is lined with ciliated epithelium 
which is raised into secreting folds, Pl. XXXVII, Fig. 11, the 
whole being contained «by longitudinal and circular muscles m. 
In the stomach these folds become brown pigmented villi (seen 
in diagram around the inside of the cavity s, in Figs. 8 and 
10) without cilia, the cells of -which are thickly distended with 
drops of secretion, their outer boundaries being blended together, 
Fig. 12, and the musculature nt becoming thicker. Of the five 
thickenings of the stomach walls usual in the thecosomatous 
pteropods, the fifth, or smallest plate, is in this genus situated on 
the dorsal side between the pair of larger dorsal plates. All are 
included in the section from which Fig. 9, Pl. XXXVII, is 
taken. Besides these five constant ones there are several other 
irregular spur-like plates of the same structure, placed sometimes 
in the spaces between the larger plates, or in either end of the 
stomach. The structure of these thickenings in the walls of 
the stomach is shown in Fig. 13, Plate XXXVIII, the section 
being figured from near the edge of one of the ventral plates, at 8 
J. I. PECK. 
about the place indicated by x in s of Fig. 9. Most exterior are 
the large nucleated fibres of the circular muscle coat, which 
control the movements of the stomach ; within these is the thick- 
ening which carries the large tooth-like plate. This thickening 
is merely an accumulation of the " gallertgewebe5,1 of the 
mollusc, as is shown by the branched cells, laid in a matrix 
which is clear; the network of cell processes is more numerous 
than is indicated in the drawing (those between the cubical 
epithelium and the muscle coat), the nuclei of which exist often 
in pairs and sometimes even in threes, as if growth were taking 
place. Placed upon this connective tissue thickening of the 
wall is a single very regular layer of cubical epithelium, which 
secretes toward the lumen of the stomach the projecting pyra- 
midal " tooth." These latter are of the same general structure 
as the casque secreted by the mantle, being hyaline, staining with 
difficulty in streaks, and containing a granular deposit. In Fig. 
13 the circular muscles, the connective tissue and the secretory 
epithelium are tinged with blue, the secretion of the " tooth " 
at that point being represented in yellow. These plates have 
been regarded as triturating structures in the pteropods, and the 
" stomach " has been called a " crop," with reason, doubtless,' in 
this case where there is no radula nor jaws at the mouth. But 
the lack of this structure (radula) does not prevent the animal 
from possessing predatory habits, for in. one of these specimens 
an adult heteropod, Firoloidea, was found, having been taken as 
food; but the stomach is usually full of diatoms, foramenifera, 
etc., of many kinds. 
The digestive gland, the " liver" of the mollusc, constitutes a 
large part of the visceral nucleus. Its wide asymmetrical opening 
into the intestine has already been described with Fig. 8, while 
the character of the cells that compose it is illustrated in Pl. 
XXXIX, Fig. 20. These are the kind described as " korner- 
zellen " by Frenzel,2 and in Cymbuliopsis they are characterized 
by large greenish-brown masses in various stages of perfection. In 
some cells there are solid, irregularly spherical, greenish masses; 
in other cells there is only an irregular central mass in a vacuole- 
1 See also Paneth, I. c. p. 255. 
2 Ueber die Mitteldarmdruse der Afollusken, Archiv fiir mik. Anat., Bd. XXV, 
p. 52. CYMB U LIO P SIS CA LCEO LA. 
9 
like portion of the cell, Fig. 20, j. They are all, doubtless, steps 
in the same process, and sometimes the whole cell is tinged with 
green without its being aggregated. I have also found these 
masses outside the cells in the lumen of the alveoli. There are also 
clumps of very large opaque granules in the peripheral portion 
of very many of the cells. There are, moreover, rods of cells at 
various points in the periphery of the liver, the cells of which 
are smaller than, and very different from the glandular portion of 
the gland, and in the centres of these rods there are small trans- 
parent masses of crystals. I could not make out the exact form 
of the individual crystals, and appearances favor the assumption 
that they are derived from the salts in solution in the blood and 
tissues of the animal, and that the rods may be in reality short 
ducts with very thick walls, but I cannot describe even their 
general direction. The blood permeates the "liver " very plenti- 
fully, as may be inferred from the large blood-vessel which sup- 
plies it, Fig. 9, ao, and which is distributed into the blood spaces 
in the walls of the basement membrane between the alveoli. 
In the centre of this digestive gland are large irregular spaces 
(Pl. XXXVII, Figs. 8-10, in the brownish lobulated mass Z), 
into which food products from the stomach may pass in the 
process of digestion. There are also tracts of ciliated liver cells, 
situated at various points along the central spaces; they line the 
passage from the intestine out into the liver, and serve doubtless 
for transporting food particles, etc., whenever they occur. Thus 
in Fig. 8 at y is seen the relative position of one of the ciliated 
pads, while the cells represented in Fig. 20 at i are taken from 
a part of the gland which projects into the central space ; the 
cells at •Z are specialized into a ciliated tract, unlike the ordinary 
cells of an adjoining fold of the liver aty. The " liver " of Cym- 
buliopsis, therefore, is something more than a mere secretory 
appendage, and comes into direct contact with the food circulated 
within it. The intestine is quite thin-walled, and lined with 
simple short columnar ciliated cells, thrown into a few villi in 
the anterior portion. 
The Central Nervous System. 
The nerve ganglia of Cymbuliopsis conform to the type of the 
Cymbuliidae in general, as it has been described in detail for 10 
J. I. PECK. 
Cymbulia,1 with some additions to the descriptions previously 
given. The general position of the ganglia in the body is shown 
in Fig. 4, n. They are very closely fused, as is shown from ventral 
view in Fig. 5, which was reconstructed from camera drawings 
of serial sections. The cerebral ganglia r. c and I. c (right and 
left cerebral) lie at the sides of the oesophagus, and are connected 
to each other around it by the large cerebral commissure cc. 
On the extreme dorsal part of this commissure, i. e. in the true 
morphological position of the cerebral ganglia, there are some- 
times a few ganglion cells remaining, but without giving rise to 
nerve trunks. From the cerebral ganglia two pairs of nerves 
are given off anteriorly into the proboscis, and one short pair 
to the otocysts below them, although this pair is much hidden 
from surface views. The more dorsal pair of cerebral nerves Cj 
go to the tentacles and supply the ganglionic swelling at their 
base. Their other pair c2 go to the proboscis, supplying the 
ciliated lips. 
The pedal ganglia-connected in Cymbuliopsis, as in Halo- 
psyche and the gymnosomatous pteropods, by a second delicate 
commissure 5-give off three pairs of nerve trunks pi~ps, which 
proceed to the fin; being smaller and supplying the proboscis. 
There is also a very delicate nerve, m, given off from the posterior 
ventral face of the pedal ganglion, and sinking almost directly 
to the ventral surface of the base of the fin. 
The nerves which pass backward into the body are derived from 
the visceral and buccal ganglia. Of the former there are three 
ganglia, giving off the four nerves 'W1-'W4, of which on the right 
side soon branches, sending one branch back into the mantle 
above, while the larger branch sinks below and supplies the mantle 
beneath the fin, and on this side carries the osphradium; is 
distributed in a similar way upon the left side of the animal, 
except that no sense organ is developed on the lower branch; v2 
comes soon to lie close to the oesophagus with the nerves from 
the buccal ganglia, with which it extends into the visceral 
nucleus, being laid in the right dorsal region just beneath the 
nephridium and circulatory organs. The large left branch v3 
bends below, and I have traced it far out into the mantle, along 
1 Recherches sur le system nerveux des Pteropodes, par Paul Pelseneer, 
Archives de Biologie, Tome VII, fasicule 1, p. 115. CYMB ULIOPSIS CA L CEO LA. 
11 
the edge and beneath the pallial gland. The fused buccal 
ganglia are situated in front of the pedal, close to the oeso- 
phagus. They give off anteriorly a pair of slender nerves b2 to 
the oesophagus, and posteriorly a similar pair, that run close to 
the wall of the stomach. 
On Pl. XXXVIII, Figs. 14-17, are figured four representa- 
tive cross-sections through the central ganglia in place. Fig. 14 
is the most posterior section, and includes the ring of cerebral 
and visceral ganglia, the former of which are represented as 
giving off the cerebral commissure cc, above the oesophagus, 
with the dotted lines; which commissure, however, has been cut 
in the preceding sections of the series. The cerebral c, pass freely 
into the visceral ganglia r.v, m.v, l.v, and they into each other. 
Among the nerve cells, located peripherally in the ganglia, there 
is in the median visceral ganglion m.v, situated upon the left 
side at k, a very large bipolar cell, whose processes may be traced 
to either side into the other ganglia. It is a constant feature of 
all the specimens examined (four) in the sections through the 
central ganglia, and in one instance had a diameter of 120/z, 
while the greatest diameter of the whole ganglion was 225/z. 
This cell, then, may be taken as presenting the qualities of all 
the cells of its kind in the periphery of the ganglia. In Fig. 18 
I have endeavored to indicate the disposition of the chromatin 
elements in the large irregular nucleus, which has perhaps taken 
its present form on account of the shrinkage of the body of the 
cell, and this is the case with many of the larger cells in section. 
One of the two or three protoplasmic processesp of this large 
cell is passed through in this section. Fig. 15 is taken ten 
sections forward. Here the otocysts o are cut in section, and the 
auditory nerve n on the right side, the fibres leading upward to 
a bunch of small cells of the cerebral ganglion ; the plane of 
section being a little oblique, the left auditory nerve was just 
previously cut in the series. The otocysts in these specimens of 
Cymbuliopsis contained no traces of otoliths, nor was the internal 
epithelium at all specialized into ciliated sensory cells, but this 
may have been caused by the action of acid in the reagents. 
Although the otocysts lie upon the pedal ganglia, yet they are 
bound to the visceral ganglion m. v by two strands of connective 
tissue from their investment. In this section also is shown the 12 
J. I. PECK. 
origin of the small nerve ?zi, whose fibres are given off from the 
large cells of the internal posterior face of the pedal ganglion ; 
also the origin of the cerebral nerve from the dorsal side of 
the cerebral ganglion I. c-not apparent in this plane through r. c. 
The buccal ganglia 1) in the median line just below the oeso- 
phagus still show a partial segmentation. 
Fig. 16 is four sections in front of Fig. 15, showing, upon the 
left side, part of the commissure cb which exists between the 
cerebral ganglia c and the buccal ganglia, and in the same 
section the point at which a similar connection is to be estab- 
lished with the buccal ganglia from the right side opposite; and 
also the origin of the pair of buccal nerves Z>2 which pass forward 
from the buccal ganglia, close to the oesophagus; also a part of 
the-elongated origin of the pair cx. The whole of the central 
nervous system, including the large nerve trunks, is sheathed 
in a thin connective tissue envelope, the small cell-nuclei of 
which are very numerous. Some of this investment cut tan- 
gently from the surface of the pedal ganglia is shown in Fig. 
16, g; it is likewise seen in all the sections as a limiting mem- 
brane of the ganglia. 
The pedal ganglia alone exist in the section from which Fig. 
17 is taken, the fibres pass from one freely into the other and 
out into the large trunks of the pedal nerves, the origin ofand 
7?2 being shown upon the left. The nerves from the cerebral and 
buccal ganglia are seen above in section, as they pass forward 
into the proboscis. 
The osphradium-Spengel's olfactory organ-of Cymbuliopsis 
is quite large and long, extending on the right side of the mantle 
as it narrows to form the opening into the inner part of the 
pallial cavity. It is composed of ciliated epithelium with gang- 
lion cells beneath, from which fibres of the nerve pass. Fig. 19 
shows the arrangement of the epithelium in two patches, a con- 
dition which obtains for some distance. There is also a ciliated 
pad of cells, Fig. 19, a, within the pallial cavity upon the visceral 
mass, of which mention will be made hereafter; but other than 
these and the tentacles, the edge of the fin and proboscis also 
serve as sensory organs, partly as organs of special sense, no 
doubt. CYMBVLIOPSIS CALC EOLA. 
13 
The Reproductive Organs. 
The position of the generative gland has already been shown 
in Figs. 8-10, h. It is distributed over the visceral nucleus as a 
uniform external layer; is divided up into large follicles by a very 
thin limiting membrane, brown pigmented in general, of which 
the internal layer-toward the liver-is more or less free from 
the general tissues of the gland, so as to form loose spaces in which 
the genital products may be carried toward the efferent duct 
and hence to the exterior. 
In the specimens of this pteropod examined, the hermaphro- 
ditic gland was in the state of female activity ; that is to say, 
the male elements had been matured and shed, while the fol- 
lowing development of ova was in process. And so there were 
no primitive germ cells developing into spermatozoa on the 
internal side of the gland, 'while the outer portion of it is filled 
with ova in all stages of maturity. The changes which take 
place in the growth of the ovum from the primitive germ cell 
are shown in the reproductive follicles figured in Pl. XXXIX, 
Figs. 22 and 23. The germinal cells destined to become ova 
enlarge-some more rapidly than others, as is shown in the 
follicle a, Fig. 22, and these latter are to complete their develop- 
ment while the other cells contribute only indirectly to the pro- 
duction of ripe ova by furnishing food material for the more 
vigorous neighboring cells. These latter cells, therefore, increase 
in size at the expense of the others, and so gradually take on the 
characters of the ripe ovum in their growth. Thus in the fol- 
licle b are seen two young ova surrounded by a layer of the other 
germinal or follicular cells; the nucleus or germinal vesicle is 
very large and clear, except for chromatin elements scattered 
about, and in the ovum upon the left of the follicle b the nucle- 
olus, or germinal spot, is cut in section, the body of the ovum 
being granular protoplasmic material. In the follicle c a still 
older stage is shown, the ovum being farther advanced, and 
evidently using the large irregular cells which it adjoins, while 
the rest of the follicle is occupied by another ovum which only 
partially appears in this particular section. 
In the further growth of the ovum, food-material is deposited 
in the protoplasm in the form of large yolk spheres, which have 14 
J. I. PECK. 
characteristic forms and markings for different thecosomatous 
pteropods.1 The markings upon the yolk spheres of Cymbuli- 
opsis give them the appearance of minute dense cells with a 
nucleus, but thickened on one border. In follicle d, Fig. 23, the 
protoplasm of the largest ovum is being furnished upon its upper 
border with the first of these yolk masses. From the beginning 
these latter are perfectly distinguishable by the manner in which 
they take the staining used, i. e. they remain untouched by the 
haematoxylin and only take the bright carmine color. Finally, 
in follicle e the ovum has acquired all the characters of ripeness, 
and in this particular section appears the large nucleus, with the 
nucleolus k, and a great abundance of nutritive material stored 
up as yolk-spheres y. After completing its growth to this stage 
it is loosened from the follicle and is ready for fertilization. 
The genital ducts and the accessory glands are diagramati- 
cally represented in Pl. XXXVI, Fig. 6. The common genital 
duct d is quite short, leading from behind down and around to 
open upward into the uterine portion of the duct -u, which itself 
leads backward on one side, into which the seminal receptacles, s. 
opens, and downward to the exterior on the other side at A. 
The two accessory glands-displaced a little downwards and to 
the left in the diagram-open very widely into the terminal 
portion of the duct. The albumeniparous gland is the smaller 
and exterior, the muciparous is the larger and interior, both 
being thrown into loose folds. The relative position of these 
organs in the visceral nucleus is shown in Fig. 4 at w, also 
in the section Fig. 10, the duct and opening being on the right 
of a median line, the accessory glands occupying nearly a median 
position in the body. In the specimen here figured the seminal 
receptacle r. s. is filled with spermatozoa, and a portion of the 
duct which connects it with the duct to the exterior (e) is cut at/* 
(although it of course soon runs out in the following sections). 
The walls of this uterine portion are much folded, brown pig- 
mented and ciliated, with a few spermatozoa visible in its upper 
portion. The genital duct d- leading from the hermaphrodite 
gland to the uterus, is cut twice in this section ; farther on in the 
series they unite with each other. Although in this mollusc 
1 See Fol, Sur le developpement des Pteropodes, Archives de zoologie exp. et 
gen., Tome IV, p. 106. CYMBULIOPSIS CALC EOLA. 
15 
there is but one genital duct common to both sexual elements, 
yet this is specialized into two portions, as seen in Fig. 24, one 
portion of a section across the duct being lined with larger 
ciliated cells than the other portion; a condition which may be 
analogous to that of those gasteropods where one part of the 
"oviduct" is specialized into the seminal groove. The duct 
becomes larger at its lower portion, as. seen in Fig. 25, where a 
few yolk spheres f, with the round marking, are included from a 
passing egg. 
The folds of the muciparous gland m are much longer than 
those of the albumeniparous gland a. The structure of these is 
further represented in Pl. XXXIX, Fig. 21, which shows that the 
cells of the one gland-the muciparous-are larger and dearer 
than those of the other, both kinds being very regularly arranged 
upon a thin basement membrane with its occasional nuclei. In 
addition to the regular basal row of nuclei of the gland cells 
there is another incomplete row of smaller nuclei n, near the 
lumen of the gland fold, which appear to belong to small cells 
wedged in between the upper portions of the large gland cells; 
in some parts of the glands these nuclei are much more numerous 
than in the figure. It was also shown that analogous small nuclei 
existed in the pallial gland cells. I do not know their meaning. 
Cilia are also present in some parts at least of the glands. 
Not only is the generative gland, in all these specimens, in a 
state of female activity, but I have been quite unable to find any 
penis to indicate that they ever function as males, or at least so 
as to effect a copulation among themselves. In the case here 
described and figured the seminal receptacle is filled with sperm- 
atozoa (in other instances it was empty) and ova are passing 
through the genital duct, but it is not probable that both the 
sexual elements were derived from the same individual gland, 
and a penis therefore probably exists in some other individuals 
functioning as males. This organ is described for the other 
Cymbuliidae as a protrusible tube lying upon the dorsal side of 
the animal, with its exterior opening a greater or less distance 
behind the tentacles; and connected with the external opening 
of the genital glands by a ciliated groove for the conveyance 
of the male element. There is indeed in Cymbuliopsis a narrow 
band of ciliated cells (Fig. 19, a) leading away from the external 16 
J. I. PECK. 
opening of the genital organs, but it beeomes less and less 
conspicuous in its anterior course until it is lost near the 
opening into the inner pallial cavity; but it does not lead into 
any groove or cavity, nor is there any indication of its relation 
to any penis, nor does the latter appear at all in the serial 
sections. This element of the structure of a functionally male 
pteropod is therefore only rudimentary, and it is possible that 
the germ cells never produce functional spermatozoa, but always 
ova, thus effecting a true separation of the sexes in many cases, 
at least, in this genus. Or perhaps the lack of a penis is only 
another one of the peculiar modifications of the mollusc, such 
as the want of a buccal armature, or the occasional lack of 
tentacles. 
The Nephridium and Heart. 
The general position of these organs in the body has already 
been indicated in Fig. 4 aty; their relations to each other are 
shown in diagram in Fig. 7, seen from the dorsal surface, the 
anterior direction being toward the bottom of the page. The 
nephridium of Cymbuliopsis is a single large loose sac lying 
above the visceral nucleus, across the pallial cavity, and bent in 
a horseshoe shape around the heart and pericardium which lie 
in front of it. Its position is quite superficial, and parts of its 
cavity are separated from the visceral mass. It is also asymmetri- 
cally disposed (the right lobe r. n being smaller than the left 
I. n)\ extending farther down upon the left side of the body 
than upon the right, Fig. 9 r. n, I. n, and extending out above 
the pallial cavity upon the right side, while the pallial cavity 
lies above it upon the left. Posteriorly its cavity extends out 
above and also beneath the pallial cavity, so it is cut twice in the 
section Fig. 8, n. It communicates upon the right side with the 
pallial cavity by a large ciliated opening o surrounded by a 
muscle, but this is the only opening that appears in the sections; 
and a second communication-with the pericardium as is the 
rule in the Mollusca-has doubtless been lost. It is also stated 
by Bronn and Keferstein that this opening into the pericardium 
has never been observed in Tiedmannia, so that in these points 
also these two genera seem to be similar. 
1 Klassen und Ordnungen des Thierreiehs-Malacozoa, p. 609. CYMBULIOPSIS CALC EOLA. 
17 
In front of and above the cavity of the nephridium, lying 
between its two large horns, is the pericardium, within which is 
the large ventricle. The pericardium begins as a recess lying 
above the nephridium, Fig. 9,pc, and broadens out anteriorly. It 
is shut off from the other parts of the body cavity by a layer of 
the connective tissue network. I have indicated in diagram, 
Fig. 7, the position of the two large blood-vessels connecting 
with the ventricle, and have called the anterior one, with a 
spacious sinus just in front of the ventricle, the auricle t\ the 
other thicker-walled vessel ao passing backward over the visceral 
nucleus is evidently an aorta leading from the ventricle to the 
liver (in section Fig. 9, ad) and the other organs (Fig. 8,<m). The 
vessel t passes far forward into the fin, becoming rather smaller 
in its course and opening out into a very loose network of large 
lacunae just anterior to the central nerve ganglia; in none 
of all the tissues indeed do the characters of the molluscan 
branched connective tissue cells appear so clearly in sections as 
in this region just anterior to the pedal ganglia. There are large 
loose spaces in the body cavity in front of and beneath the ven- 
tricle, and I had expected to find in one of these the auricle of 
the circulatory system as it has been described in pteropod 
anatomy-i. e. as being an incompletely closed sinus into which 
the blood from the tissues is collected and from which it passes 
into the ventricle; but the sections of the material at hand 
were insufficient to warrant such conclusions. Furthermore, 
these spaces before mentioned contain certain lateral and dorsal 
areas of closely aggregated cells that do not differ much, except 
in greater size and abundance, from the other cells about the 
visceral organs, but which present a peculiar appearance in sec- 
tion through their mass. Their significance I cannot determine 
by a study of this form alone. 
The lack of material is my only plea for the insufficient way 
in which the circulatory system of Cymbuliopsis has been followed 
up, and for the incomplete nature of the sexual differences. But 
in other respects it is hoped that the general pteropod structures 
have been indicated; and this genus seems to be generally typical 
of the whole family. 18 
J. I. PECK. 
Explanation of Plates. 
Fig. 1. Surface view of Cymbuliopsis from dorsal side; p pro- 
boscis, t tentacles, 1-3 muscle bands. 
Fig. 2. Casque, from dorsal position when in place. 
Fig. 3. Diagram of the parts in place, from ventral view, twice 
the natural size; p.g pallial gland with the bands across it, k the 
pallial cavity entered by a narrowed opening behind the pallial gland 
from this view, z the dark aboral ring. 
Fig. 4. Diagram of the organs in place in optical section from the 
right side; m mouth, t tentacles, n central nerve ganglia, / nephri- 
dium with heart in front of it, k casque within the layers of the 
mantle, i intestine, w accessory genital glands, y opening from large 
to the interior pallial cavity,p.g pallial gland. 
Fig. 5. Central nervous system: px-p3 pedal nerves, cx-c2 cerebral 
nerves, h-b.2 buccal nerves, -v± visceral nerves, m small posterior 
pedal nerve, s small pedal commissure, o otocysts, r. c, I. c right and 
left cerebral ganglia, cc cerebral commissure. 
Fig. 6. Diagram of genital duct and accessory glands, d genital 
duct, r. s seminal receptacle, u uterine portion of the duct, h external 
opening. 
Fig. 7. Diagram of nephridium and heart from dorsal side; 
t auricle, v ventricle, pc pericardium, ao aorta, o opening into pallial 
cavity, r. n, I. n right and left lobes of nephridium. 
Fig. 8. Section across the more posterior part of the visceral 
nucleus; mantle and pallial cavity put in in diagram; k external 
layer of mantle, w internal layer of same, lining the pallial cavity, s 
stomach, i intestine, h hermaphroditic gland, ao aorta, n nephridium 
cut in two parts at this point, I liver-the letter itself being placed 
in one of the spaces of the same; y one of the ciliated projections 
of liver cells. 
Fig. 9. Section through about the middle of the visceral nucleus; 
r.n, l.n right and left portions of the nephridium, pc pericardium, 
a anus, other letters as in the previous figure. 
Fig. 10. Section across a more anterior portion of the visceral 
nucleus; v ventricle, m folds of the muciparous gland, a of the albu- 
meniparous gland, ddx genital duct cut in two places, r. s seminal 
receptacle, f fragment of uterus, e leading to the external opening, 
other letters as before. 
Fig. 11. Folds of lining of oesophagus; m muscle fibres, circular 
and longitudinal. 
Fig. 12. Villi of beffinnine of stomach : m muscles. CYMBULIOPSIS CALCEOLA. 
19 
Fig. 13. Portion of a thickened part of stomach wall, with secretion. 
Fig. 14. Section through posterior part of central ganglia; c cere- 
bral ganglia, r. v, I. v right and left visceral, m. v median visceral 
with the large ganglion cell k, bY buccal nerves, co cerebral com- 
missure, oe oesophagus in outline. 
Fig. 15. Section through about the middle of the central ganglia; 
r. c, I. c right and left cerebral ganglia, origin of the pair of nerves 
Ci, b buccal ganglia, l.p left pedal ganglion, m.v median visceral, 
o otocysts, n auditory nerve. 
Fig. 16. Section taken four sections anterior to that of the last 
figure; c cerebral ganglia, r.p, l.p right and left pedal, cL origin of 
the nerves cn b.2 origin of the nerves b2 from buccal ganglia, cb cere- 
brobuccal connective, g connective tissue sheath of ganglia. 
Fig. 17. Section through the pedal ganglia (r.p, l.p) with origin 
of large nerves cut upon the left side, ctc3 cerebral nerves, b2 buccal 
nerves. 
Fig. 18. Large ganglion cell; p protoplasmic process. 
Fig. 19. The osphradium with nerve. 
Fig. 19g. Ciliated band on the visceral nucleus. 
Fig. 20. " Liver" cells; i with specialized ciliated cells,/ordinary 
secreting cells, with various cell contents. 
Fig. 21. Section across the folds of the accessory genital glands; 
m muciparous, a albumeniparous gland, n the smaller exterior 
nuclei. 
Fig. 22. Growth of ovum; a, b, c successive stages in a series of 
follicles. 
Fig. 23. d, e older stages in the same series, y yolk spheres, k 
nucleolus. 
Fig. 24. Section across the genital duct; large muciparous gland 
cells in outline. 
Fig. 25. Through lower portion of the genital duct; /yolk spheres 
of a passing egg. 
Fig. 26. Section in pallial gland; t the cells of the dark areas, 
v those of the lighter transverse bands, n small exterior nuclei. 
Fig. 27. Vertical section through one rim of the aboral ring, 
m muscle fibres. STUDIES FROM BIOL.LAB. 
. VOL.IV PLATE XXXVI 
Fig. 3 
Fig. 2 
Fig.l 
Fig A 
Fig. 6 
Fig. 7 
Fig. 5 STUDIES FROM BIOL. LAB. 
VOL.IV. PLATE XXXVII. 
Fig.9 
Fig. 8 
Fig. 10 
Fig. 12 
Fig- 11 STUDIES FROM BIOL.LAB. 
VOL.IV. PLATE XXXVIII 
Fig. 19 a 
Fig.19 
Fig. 13 
Fig.lg 
Fig. 16 
Fig. 14 STUDIES FROM RIOL. LAB 
VOL.IV PLATE XXXIX 
Fig. 
Fig. 21 
Fig. 23 
Fig. 20 
Fig. 26 
Fig. 25 
Fig. 27 
Fig. 2 4