Anatomy and physiology of Anodonta fluviatilis

New York State Museum or Narturat History.

[Extracted from the Thirty-fifth Annual Report. ]

ANATOMY AND PHYSIOLOGY

OF

ANODONTA FLUVIATILIS.

By GEORGE B. SIMPSON.

WITH ELEVEN PLATES.

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ANATOMY AND. PHYSIOLOGY

OF
AWN ODDIOUNGT TA TO Vi TeART TS LES;

By GeorGE B. SIMPSON.

ANODONTA FLUVIATILIS.

Several years ago while making a collection of fresh-water shells, I
naturally desired to know something of their anatomy and physiology. I
found no book treating specially of that subject, though I found one or
more chapters in several books, but to me they did not seem to
be just what was needed by a beginner, the articles were either without
illustrations or the illustrations were few and very poor. I have written
this article with the hope that it may be of use to beginners, and also
to some who have contented themselves with collecting the shells
paying no attention to the living animal within. To those who are ad-
vanced in similar knowledge, this article may seem simple, but it must
be remembered that very simple things are frequently formidable to
beginners. I had intended to follow this article with others on the an-
atomy and physiology of other bivalve and univalve shells, but the delay
in printing has been so great that I have not done so. At that time I
was more interested in Unionida, and selected one of their number,
Anodonta fluviatilis, for dissection and explanation.

By boiling the animal for a short time, the intestinal canai, nerves,
arteries, etc., are much more easily found than by dissecting an alcoholic
specimen; though the animal is distorted by boiling still a very good
idea of the position of the different organs is formed, and the dissection
of a specimen which has been kept in alcohol for some time is rendered
much easier, the student knowing just where to look for the differ-
ent organs: to dissect an animal just from the water would be almost
if not quite impossiblefor a beginner. A very slight addition of
chromic acid to the alcohol in which some of the animals are kept, will
be of help in dissecting certain parts.

[Sen. Doc. No. 38. ] 22

170 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

All dissections were made by myself, and all the drawings are
directly from nature by myself; only in two or three instances has the
microscope been used, nearly all the parts described can be seen with-
out the use even of a simple lens.

The Anodonta consists of an outer part called the shell or exo-skeleton,
and the animal inclosed within the shell. The shell is composed of
two valves united dorsally by means of an elastic ligament.

The parts of the animal which will be described in detail are the man-
tle, gills, labial palpi, muscles, body, foot, viscera, nerves, liver, stomach,
heart, pericardium, renal organ, vascular system and organs of genera-
tion.

When the shell of the Anodonta (and these remarks apply also to the
genera Unio and Margaritana) is held with the ligament or attached
portions of the shells upward, and the larger, most convex portion, the
most distant from the eye, the valve at the right hand is called the
right valve (Pl. 4, fig. 1, r.v.); that at the left, the left valve (PI. 4, fig.
1, 1. v.); the part the most distant from the eye, the anteror portion
(Pl. 4, fig. 1, a. p.); the nearest to the eye, the posterior portion (PI.
4, fig. 1, p. p.) ; the upper part the dorsal (PI. 3, fig. 1, d. p.), and the
lower part the;ventral portion. Where the same letters occur on PI.
3 as on Pl, 4, the same parts of the shell aredesignated. On the dorso-
anterior portion of each valve is a more or less prominent, blunt
elevation called the umbo or beak. (Pl. 3, fig. 1, umb.)

Posterior to the umbones, uniting the dorsal margins of the valves,
is an elastic horny portion of the exo-skeleton, designated the hgament
(Pl. 4, fig. 1, lig.), which antagonizes the action of the adductor mus-
cles, and has a tendency to keep apart the ventral margins of the
valves.

The ligament when the shell is.open is of nearly equal thickness;
when the shell is closed by the action of the adductor muscles, the
outer portion of the ligament becomes stretched and the inner por-
tion compressed and folded; when the muscles relax, the ligament
assumes its natural form and in doing so draws apart the ventral mar-
gins of the shell.

The ligament is said to be external, though it is covered for about one-
- half of its width by an extension of the shell. This ligament is com-
posed of two parts, the outer and thinner portion the epidermal,
and the inner portion the cartilagenous, composed of both perpen-
dicular and horizontal fibres.

The shell or exo-skeleton consists of three distinct layers, the outer
one is designated as the epidermis (Pl. 4, fig. 3), and consists of a thin
membrane which is uncalcified, that is, without lime in its composi-
tion, and varying in color from olive green to brown, Immediately

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 171

beneath the epidermis is the prismatic layer (Pl. 4, figs. 4, 6, pr.),
seemingly composed of solid prisms, but if this portion of the shell is
placed in dilute acid the interior of each prism is dissolved, leaving
the walls entire, showing that the layer is made by the deposition of
calcareous matter in prismatic, generally hexagonal cavities, which are
themselves formed by the superimposition of fenestrated lamina,
secreted by the margin of the mantle. (PI. 4, fig. 6, pr.)

The third or inner layer of the shell is formed by the superimpo-
sition of very thin diagonal layers, which overlap each other and is
known as nacre or the nacreous layer. (Pl. 4, figs. 5, 6, nac.)

The interior of the shell presents an irridescent appearance, which is
caused by the refraction of the light by the edges of the overlapping
layers. The prismatic portion being secreted by the edge of the
mantle extends slightly beyond the nacreous portion. If any thin
shell is held to the light the prismatic portion can easily be seen
with the aid of a simple lens. Near the margin of the shell, the
prismatic portion is the more prominent, while on all other portions
the nacreous layer is thicker than the prismatic, ae from two to
four times the thickness.

The epidermis (Pl. 4, fig. 3), shows no structive: though showing
under the microscope pigment cells (Pl. 4, fig. 3, p.c.), being with-
out lime in its composition, it serves to resist the action of carbonic
acid gas, which is contained in greater or less quantities in all fresh
water, and which, but for the protection of the epidermis, would de-
stroy the nacreous and prismatic portions of the shell. On portions
of the shell, generally the umbo, from being the longest exposed,
where the epidermis has been worn away, the shell is often much eroded.
The same conditions occur on other portions of the shell where by acci-
dent the epidermis has been broken away. Sometimes between the other
layers the animal secretes a layer of epidermis, thus arresting the
progress of erosion; layers occurring in this manner are usually colorless.

The formation of the shell, according to all or nearly all the
writers on this subject,is not continuous, but occurs at successive
periods; but this explanation is not entirely satisfactory. The secre-
tion of the shell is involuntarily performed by the animal and can no
more be arrested by the will of the animal than the formation of
‘bone in the human body can be continued or not according to the will.

There are numerous elevations on the exterior of the shell; in thin
shells these elevations have corresponding undulations in the interior.
The shell of the Anodonta being usually very thin, the interior cor-
responds in form to the exterior. The Anodonta is without the
teeth of the Unio or Margaritana, but below the ligament there are
two thickened projections or rudimentary teeth. (PI. 11, fig. 1, r.t.)

172 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

On the interior of the shell, near the anterior dorsal margin, is seen
a comparatively large oval marking, caused by the attachment of the
anterior adductor muscle (PI. 11, fig. 1, a.a.); just posterior to this are two
other impressions, one at the upper and the other at the lower por-
tion ; the upper one is caused by the attachment of the anterior retractor
muscle (Pl. 11, fig. 1, a. r.), the lower one by the attachment of the
protractor pedis muscle (Pl. 11, fig. 1, p.p.), and are known respectively
as the anterior retractor and the protractor pedis muscular impres-
sions.

At a short distance from the post-dorsal margin, near the angle
formed by the junction of the hinge-line and posterior slope, is another
large marking formed by the attachment of the posterior adductor
muscle (P]. 11, fig 1, p. a.), and is known as the posterior adductor
muscular impression. Immediately anterior to the upper portion of
this impression, is a smaller nearly circular impression, formed by
the attachment of the posterior retractor muscle and is known as the
posterior retractor muscular impression, (Pl. 11, fig. 1, p. r.) Extend-
ing from the umbo to each adductor muscular impression, is a faint,
gradually enlarging marking, caused by the adductor muscles,
forming continuous impressions as they changed their position
with the advancing growth of the shell. (Pl. 11, fig. 1, mar.) Connecting
the posterior and anterior muscular impressions is a line, corresponding
in curyature with the ventral margin of the shell, known as the pallial
line, and formed by the attachment of the mantle to the shell by means
of numerous muscles along this line. (Pl. 11, fig. 1, p.1.; Pl. 5, fig. 1,
p- 1.) Near the umbo are several impressions caused by the attach-
ment of adductor muscular fibres. (PI1.11, fig. 1, m.f.)

The thickness of the shell varies in different localities, even when only
a short distance apart, and does not depend upon the amount of lime
(of which substance the shell is principally formed) in the water,
but upon the power of the animal to absorb, and assimilate it
into ashell; thin fragile specimens being found in water, rich in
lime, and others more massive, in waters where that material is
much less abundant. That the thickness of the shell is not due to
the amount of lime in the water is shown by the fact that several
species occur in the same stream, some having massive and others
fragile shells; Unio undulatus having a shell one-fourth of one inch
or more in thickness, and Unio gracilis with a shell one-twentieth of
an inch in thickness, occur in the same locality. The conditions
favorable for the development of one species may be unfavorable for
the development of another, even of the same genus. In the canal at
West Troy, N. Y., specimens of Anodonta implicata are found of
very large size, the shells free from erosion, while Anodonta fluviatilis,

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 173

though of frequent occurrence, is always small, seldom or never exceed-
ing three inches in length, thin and much eroded. All the species
occurring at this locality, with the exception of A. fluviatilis, viz., A.
implicata, U. complanatus, U. radiatus, U. ochraceous, U. cariosus
and U. nasutws occur in much better condition than in any other
locality in this part of the State. In a pond situated less than a mile
from this locality, A. fluviatilis is found of unusually large size and
but slightly eroded ; specimens five inches in length, with a height
of three inches and a diameter of two and one-half inches are abundant,
and some are found measuring more than six inches in length and
three and one-half inches in height, as large and perfectly preserved
Specimens as occur in any locality, while with the exception of this
species there is not another shell, in the pond, either bivalve or
univalve. In another locality a mile below Albany where Spherium
rhomboideum is found in abundance and of unusually large size,
Anodonta fluviatilis, though of frequent occurrence, is very small ;
the largest specimen I have seen, among a collection numbering many
hundreds, measures two inches in length. ©

A, fluviatilis thrives best in ponds, but is found in quite rapid
streams, though even then the most favorable localities are in the
comparatively quiet portion of the stream.

The largest specimens I have seen, were found in the pond mentioned
above, near the mouth of a sewer, where the mud was of a slimy char-
acter and offensive to the smell. It is claimed that the male and
female may be distinguished by the comparative diameter and gen-
eral shape of the shell, but I have not been able to so distinguish
them. In the fall of 1879 I collected about one hundred and fifty
specimens of varying size—the shells were of different shapes and
proportions, some quite flat, others extremely gibbous, the diameter
sometimes being greater than the height. Among the first sixty I
opened, there was not a single male, the outer gills of each specimen
being filled with young. The remaining specimens were placed in a
tank, and for several months undisturbed ; when I removed these ani-
mals from the shells I found only four individuals without young in
the outer gills, and as some of the animals had extruded a portion of
the young from the gills, it is possible that the individuals above men-
tioned may have had the young in the gill pouches earlier ‘in the sea
son but had extruded them all. Though I am not prepared to say
that the sexes are not distinct, the fact that nearly every specimen
had young in the gills would seem to indicate that condition.
When my attention was first called to it, it was too late to make any
farther collections that season. The growth of an animal during a
year, I have not been able to determine ; an individual which I have

174 'THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

kept for ten months has gained in length in that time only one-fourth
of an inch, but it seems probable that their growth in their natural
habitat must be much greater than this.

In a certain locality in a stream near Albany, Unio pressus is quite
abundant in a rapid portion, about two hundred feet in length.
I have collected all the large specimens each year for three years. The
water being so shallow that every portion of the bottom can be seen,
and yet each year they appear equally abundant and of full size, show-
ing that their growth must be quite rapid.

When out of water, and exposed to the sun, the Anodonta will live
but a short time; placed in a cool, somewhat damp situation, life will
continue for several days. Other members of the family Unionide are
much more tenacious of life. According to DESHAYEs, de Conch, pp.
81-84, a specimen of Anodonta from Cochin China reached Paris in
a living condition after having been wrapped in dry paper for a period
of more than eight months; similar instances are mentioned concerning
Unio litoralis (Drap.), Spatha rubens (Lam.) and an Australian species
of Unio, the last surviving two hundred and thirty-one days. None of
those with which I have experimented have survived more than seven
days, and the greater portion of them died within two or three days.

The popular belief that the removal of a bivalve from the shell is
instantly fatal to the animal is erroneous. While making the draw-
ings illustrating this article, I cut through the muscles attached to one
of the valves, removing the valve; and, after some hours occupied in
making the drawing (Pl. 5), I removed the animal entirely from the
shell, cutting away the mantle from one side, and spent about an hour
in noting the action of the ventricle and auricles. The action of the
heart at this time, eight hours after the valve was removed, was full
and regular.

The heart continues its action for a considerable time after all appar-
ent muscular force has been lost. I once noticed in the tank one of
the Anodonte, to all appearances dead, the shell gaping, the foot pro-
truding, no contraction occurring on handling, and no evidence of life
apparent. Not having time to dissect it that day, I laid it away in
cold water ; about twenty-four hours afterward Iremoved the animal
from the shell, not the slightest contraction occurring, and yet the
heart was distinctly beating, though slowly.

THE MANTLE.

(Plate 6.)
If a shell be opened by inserting a knife between the valves and
cutting, close to the shell, the anterior and posterior muscles, a thin,
semi-transparent membrane will be observed completely investing the

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 175

animal and lining the interior of the shell, extending between the
rudimentary teeth of the Anodonta and the strong teeth of the Unio
and Margaritana. This membrane is called the pallium or mantle.

The mantle is divided into two lobes, each one lining a single valve of
the shell; they are united along the dorsal portion, and free along
the ventral portion, and are pierced by the anterior and posterior
adductor muscles.

The mantle is attached to the shell by small muscles near the umbones
or beaks and along the pallial line.

The impressions left by the umbonal muscles on the shell are com-
paratively faint; those left by the muscles of the pallial line are fre-
quently quite distinct. ‘The edges of the mantle meet on the upper por-
tion of the anterior adductor muscle, and shortly blend, showing the
line of junction by a narrow, slightly elevated ridge, which continues
for nearly one-half the distance to the posterior muscle, then becoming
stronger, more elevated, gradually increasing in height and width to
a point a little anterior to the posterior adductor muscle. At this
point the edges become free, though the lobes are united below; the
edges at first lie close together, but gradually become more separated,
continuing thus to the posterior part of the shell, where they are
entirely free.

The ridge on the dorsal portion of the united mantle is caused by ~
the insertion of the mantle between the rudimentary teeth. Behind
the body of the animal the outer lamelle of the gills are attached to
the mantle lobes, the inner lamell to the outer lamellx of the inner
gills, the inner lamellz of the inner gills are attached to each other,
thus forming a connection between the lobes, and dividing the space
between them into two parts or cavities. The inferior and largest cavity
is known as the branchial or pallial chamber ; the superior is known as
the anal or cloacalchamber. At the posterior portion of the branchial
and cloacal chambers are situated, respectively,the rudimentary ventral
or inhalent siphon (Pl. 5, i.s.) and the dorsal or exhalent siphon
(Pl. 5, e. s.) formed by the thickened portion of the mantle, just within
the edge, which is capable of considerable expansion and contraction,
When the animal is undisturbed the shell is generally slightly opened,
the siphons expanded and projecting beyond the edges of the valves
(Pl. 3, i.s.). The portion of the mantle representing the inhalent siphon
has numerous tentacles (Pl. 3,1.s.; 4, fig. 9), which are developed from
the inner portion of the mantle. On the exhalent siphon they exist only
in a rudimental state, though in some species of Unio the tentacles
on the exhalent siphon are of nearly or quite the same strength as the
tentacles of the inhalent siphon. The tentacles of the inhalent siphon,
in a moderate sized specimen of this species, are about two mm.in length

176 T'HIRTY-FIFTH REPORT ON THE StaTE Museum.

and .35 mm. in diameter, consisting generally of a hollow tube, largest at
the base and gradually diminishing in size to the end; occasionally they
are forked at the end, They are covered with cilia or microscopical fila-
ments, which keep up a rhythmical motion, causing currents of
water to constantly enter the branchial chamber. The two lobes of the
mantle are not joined below the inhalent siphon. The lower por-
tion of the exhalent siphon is formed by the uniting of the gills;
the upper portion by the uniting of the two lobes of the mantle.

On the dorsal part of the animal is an essentially oval space, which is
the pericardial cavity. The portion of the mantle over this space is ex-
tremely thin and quite transparent. The rest of the mantle to the
pallial line is thicker, but still semi-transparent ; from the pallial line
to the free edge, the mantle is considerably thickened ; at the edge it
is very much thickened, and is divided into two portions or lips, be-
tween which is a smaller ridge. The epidermis is deposited by that
portion of the mantle consisting of this ridge, a fringe of the epider-
matic layer being usually found adhering to it. The prismatic layers
are deposited by that portion of the mantle nearest the edge; the
nacreous layers by the other portion of the mantle. Numerous blood
vessels extend through the mantle, frequently branching and anasto-
mosing (PI. 5, v.e.). Below the pallial line, in the thickened portion
of the mantle, are numerous radiating muscular fibers, more plainly
apparent on the posterior portion (Pl. 5, m. f.).

The mantle is also supplied with nerves proceeding from the cerebral
and posterior ganglia (Pl. 5,a. m. n., p.m. n.) which will be spoken of
more fully under the head of the nervous system.

The mantle is composed of two layers, the inner one consisting of
ciliated epithelium cells, and the outer and shell-producing layer con-
sisting of non-ciliated cylindrical cells.

THE CILIA.
(Plate 7, fig. 1.)

The cilia are extremely minute and delicate hair-like processes, varying
in length from zg455 to zy Of an inch. The name is derived from
the Latin word ciliwm, an eyelash. The cilia, during life, and some-
time after death, keep up a constant, rapid, regular motion. Water
or any fine substance coming in contact with them is rapidly propelled
in the direction of the movement of the cilia.

Cilia occur not only in mollusca, but also in mammals, birds, rep-
tiles, actinia, echinoderms, etc. The motion of the cilia does not
cease with the death of the animal, but if the parts are kept moist
the motion will continue for some time afterward. In examining the

ANATOMY AND PHYSIOLOGY oF ANODONTA FLUVIATILIS. 17%

gills of an Anodonta, about thirty hours after they had been removed
from the animal, in the meanwhile remaining in water, the movement
of the cilia was apparent, as regular and rapid as during the life of
the animal ; how much longer the movement’ may have continued I
do not know.

The cause of the rapid, rhythmical motion of the cilia has not been
satisfactorily explained. ‘This movement continues after the apparent
death of the animal. The integrity of the cells to which they are
attached is necessary to the movement, for as soon as these shrink
from want of moisture, or are destroyed from any cause, the movement
of the cilia ceases.

The cilia occur on the inner side of the mantle, on the labial palpi,
the foot, tentacles of the siphon, the margins of the plates of the
outer side of the gills, in the mouth, stomach and alimentary canal,
and on the tentacles of the siphon. If a few grains of any colored mat-
ter, for instance, carmine, is placed in the water near the posterior
portion of an Anodonta, as it lies in the water in its natural position
with the shell slightly expanded, it will be observed to enter the bran-
chial cavity, and in a short time afterward to pass out at the exhalent
siphon. The cause of this is the action of the cilia. The movement
of the cilia on the interior of the mantle is toward the anterior end,
and the water entering the branchial siphon is consequently forced in
that direction. The movement of the cilia on the margins of the
plates of the gills is from the ventral to the dorsal portion, and by
them a portion of the water being forced toward the anterior end, is
diverted from its course and passes over the gills from their ventral to
their dorsal :margins, aérating the blood in the capillaries. From the
dorsal portion of the gills to the posterior portion, the movement of
the cilia is toward the posterior end; in this manner the water which
has passed over the gills is forced out through the dorsal siphon.

The portion passing to the anterior part of the animal is conveyed,
by the action of the cilia of the palpi to the mouth, by the cilia of
the mouth and cesophagus into the stomach, and from the stomach
through the intestinal canal, passing out of the anus; the nutritive
portion having been digested and assimilated.

Moura, SromacH, ALIMENTARY CANAL.
(Plates 6, 10, 11, 13.)

The mouth or oral aperture consists of a broadly oval, nearly circu-
lar, horizontal aperture (Pl. 6, m., Pl. 13, figs. 4, 5, m.), situated in the
anterior portion of the body, just beneath the adductor muscle. The
mouth is simply an opening or cavity, without any trace of a mastica-

[Sen. Doc. No. 38.] 23

178 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

tory apparatus. The lining of the mouth consists of ciliated epi-
thelium cells, continuous with the labial palpi, or, as they are desig-
nated by some authors, the oral tentacles. The mouth connects with
the stomach by a very short esophagus, the lining of which also con-
sists of ciliated epithelium, the food being conveyed to the stomach by
the action of the cilia.

The stomach (Pl. 6, s.), which is situated just back of the anterior
adductor muscle, is irregular in shape, the general form being round
or oval, with several depressions and plications which are stronger
on the inner surface. The stomach is invested by the liver (Pl. 6, 1.),
with which organ it is connected by the minute orifices in the
cecal tubes of the liver. On the right side, the stomach communi-
cates with a blind sac, the nature and use of which body is not defi-
nitely known. It varies in size at different times of the year, being
found most prominent after winter. Various explanations and con-
jectures have been made regarding the use of this organ, but nothing
is known with certainty. The general direction of the esophagus and
stomach is toward the dorsal margin.

The intestine proceeds from the left side of the stomach ; as soon as
it leaves the stomach it turns downward at an angle of a little more
than 45 degrees to the hinge-line (PI. 6, fig. 1, i. ¢.).

The measurements given below are from a specimen, the body and
foot of which combined are five centimetres in length and three in
width ; of course in larger and smaller specimens, the individual
measurements would be different, but the comparative measurements
would be the same.

The intestine proceeds from the stomach downward and backward
with a slight curvature till within a short distance of the posterior
margin of the body, a little above the foot ; it then turns toward the
dorsal side for a short distance, corresponding in curvature to
the margin of the body. At about midway between the dorsal
and ventral margins of the body (that is, the body proper and the
foot), the curvature is toward the anterior and so continues to a point
five millimetres below the renal organ, and a. little less than two centi-
metres posteriorly to the stomach — for this distance the intestine is
small, being about one millimetre in diameter. At this point
the dorsal part of the intestine is slightly prolonged and firmly at-
tached to the surrounding mass (PI. 6, fig. 1, i. é.). The intestine
here turns abruptly toward the right side and continues in that direc-
tion for the distance of three millimetres, then turning backward
and continuing just posterior to and nearly parallel with that portion
previously described to a point about two-fifths the length of the body
from the mouth, where the ventral portion is slightly prolonged and

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 179

attached to the surrounding mass (PI. 6, fig. 1, i. é.). The intestine
thence turns abruptly toward the right side of the body. The portion of
the intestine last described is somewhat larger than that first described,
being about two millimetres in diameter, and at the point where it turns
toward the right side it becomes somewhat clavate in shape, and is
three millimetres in diameter : after turning to the right side it almost
immediately turns toward the dorsal and posterior part of the body,
crossing the portion first described nearer to the right side, con-
tinuing in this direction for the space of twenty millimetres, then
curving toward the anterior. At this part the intestine is small,
being about one millimetre in diameter. Almost immediately beyond
the point where the direction of the curvature is toward the anterior,
the intestine turns toward the left side and abruptly enlarges to a
diameter of about five millimetres and continues nearly to the dorsal
margin, parallel to and nine millimetres from that portion of the
intestine proceeding from the stomach toward the post-ventral margin
of the body. The intestine gradually becomes smaller as it approaches
the dorsal surface, at that point being a little more than three milli-
metres in diameter; it here turns abruptly backward, leaving the
body and passing through the ventricle, though entirely unconnected
with that organ, thence over the posterior adductor muscle, and ending
just beyond that muscle, opening into the cloacal chamber.

The intestine after leaving the body is called the rectum (PI. 6, r.),
the opening at the extremity is the anus (PI. 6, a.).

The lining membrane of the intestine, throughout its entire length,
has numerous strong transverse folds. On that portion of the intestine
nearest to the ventral margin, a ridge commences which continues to
the extremity.

Digestion takes place in the stomach, and the nutritive matter
evolved transudes through the walls of the intestine and thus enters
the system.

Tuer LABIAL PALPI.
(Plate 13.)

The labial palpi consist of two pairs of thin contractile, foliated
lobes, two on each side of the body (PI. 13, fig 5, 1. p.). They are
subtriangular in outline. The widest portion situated posteriorly.
The following measurements are of the palpi of an animal eight cen-
timetres in length: length, 17 mm., width at posterior portion, 8 mm.,
rapidly narrowing to the oral cavity (Pl. 11, fig. 3). The onter
lamina passes above the mouth, the inner below, each becoming con-
tinuous with its fellow on the opposite side, and continuous with the
lining membrane of the mouth and forming lips to that organ (PI. 13,

180 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

fig. 5). The dorsal margins of the outer palpi are attached to the
inner face of the mantle, that of the inner laminz to the foot. The
outer and inner palpi of each side of the animal are united along a
line designated by dots on fig. 6, Pl. 13. The outer faces of the
lamin are smooth and consist of a thin layer of epithelium ; the
inner faces, for two-thirds the length from the posterior portion, are
strongly ridged transversely ; the free edges of the palpi being crenu-
late. There are about eighteen ridges in the space of five millimetres.
The summits of the ridges have comparatively large vibratile cilia (Pl.
13, fig. 7). Ata point two-thirds of the length of the palpi distant
from the posterior ends the transverse ridges abruptly terminate, and
from that point to the mouth the ridges are irregular and longitudinal,
also ciliated. When the animal is living the inner face of the outer
palpi and the outer face of the inner palpi are slightly distant from
each other. The current of water which contains the minute animal
and vegetable substances constituting the food of the Anodonta, is by
the cilia of the transverse ridges of the palpi carried toward the
mouth, and by the action of the cilia of the longitudinal ridges di-
rectly to the mouth, and then by the cilia of the lining membrane of
the oral cavity and short esophagus, to the stomach.

THE LIVER.
(Plates 4, 6.)

~ The liver invests the stomach (PI. 6, fig. 1, 1.), and consists of a
greenish brown sponge-like mass, formed of cxca or tubes arranged
in racemose clusters, and communicating with the stomach by means
of minute orifices ; the czeca or tubes (Pl. 4, figs. 7, 11) are lined with
epithelium cells.

The liver is abundantly supplied with blood and from the blood the
cecal tubes extract a fluid which resembles the bile of animals of
higher organization, which fluid enters the stomach by means of the

orifices previously mentioned, and aids in the process of digestion.

THE RENAL ORGAN.

(Plate 9.)

The renal organ, or organ of Bojanus is situated immediately below
the pericardium. It is thus called after the name of its discoverer,
Bojanus. This name has not been universally adopted and I shall use
the term renal organ as being more appropriate.

The renal organ consists of two symmetrical lateral parts. Each
part is separated into two chambers, the upper and the lower.
The upper is the smaller and known as the non-glandular or pleural

ANATOMY AND PHYSIOLOGY oF ANODONTA FLUVIATILIS. 181

sac (Pl. 9, fig. 4, n. g. s.), the roof of which is formed by the floor
of the pericardium. It is filled with water and is separated from the
glandular portion by a thin transparent wall. The glandular sac is
situated immediately below the non-glandular sac, and is filled with
dark brown, nearly black granular matter (Pl. 9, fig. 4, g.8.). The
non-glandular sac extends only to the posterior portion of the pericar-
dium. ‘The glandular sac extends below and in front of the posterior
adductor muscle, and invests the tendons of the posterior retractor
muscles, In the floor of the pericardium immediately below the place
where the intestinal canal enters the body, are two small oval open-
ings, with tumid lips (Pl. 9, figs. 4, 5, 7 0. p.g.). These openings commu-
nicate with passages through the glandular sac. (Pl. 9, figs. 4-7, o. p. g.)
Near the posterior portion of the glandular sac these passages enter
the non-glandular sac. (Pl. 9, figs. 4, 6,'7,0.e.s.) In the anterior portion
of the non-glandular sac is a small opening which communicates with
the epibranchial chamber, just back of the attachment of the inner
gill to the body. (Pl. 9, figs. 4-7, 0. b. ec.) It will thus be seen that
the pericardium indirectly communicates with the exterior. This
arrangement will be more distinctly understood by referring to Pl. 9,
fig. 7, where the passage is represented as a tube.

The walls of the vena cava are traversed by numerous small blood-
vessels which pass from the vena cava to the gills,

The renal organ is, in all probability, analogous to the kidney of
vertebrate animals. Its functions will be again spoken of under the
head of circulation of the blood.

PERICARDIUM, HEART.

(Plate 9.)

From a point on the dorsal portion of the body just posterior to the
umbo, to the posterior adductor muscles, is an oval cavity about twice
as long as wide, inclosed above by the thin semi-transparent part of
the mantle, and filled with a colorless fluid. This cavity is the peri-
cardium (Pl. 9, figs. 1, 2, 3, p.), and differs in some important re-
spects from the analogous organ in man and other vertebrate animals
in which it consists simply of a sac filled with a fluid, facilitating the
movements of the heart, while in the Anodonta and mollusca gener-
ally it contains blood as well as other fluid matter, and connects indi-
rectly with the exterior. The movements of the heart may be observed
through the thin mantle — when the mantle is removed the heart is
laid bare. It consists of one median and two lateral chambers, re-
spectively named the ventricle and auricles. (Pl. 9, figs. 1, 2, 4, v. au.)
The ventricle is a sac of yellowish color, oval in form, contracting

182 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

and expanding, not regularly and every portion at once, but
in a peristaltic manner. In contracting and expanding the ventricle
assumes different shapes, from nearly circular to elongate-oval. Con-
tinuing through the middle of the ventricle can be seen a portion of
the rectum ; at the anterior portion where the rectum enters, the ven-
tricle is narrow, scarcely more than the diameter of the rectum. From
the ventricle proceed two comparatively large tubes (PI. 10, fig. 1, a.ao.,
p-ao.) the anterior and posterior aorte. The anterior aorta (Pl. 10,
fig. 1, a, ao.), leaves the ventricle immediately above the intestine, and
enters the body in close contiguity to that organ. The posterior
aorta passes below the rectum. The walls of the ventricle consist of
two thin layers of epithelium, between which isa layer of muscular
fibre, in which are delicate nerves proceeding from the posterior
ganglia,

The auricles consist of nearly transparent sacs, pyramidal in form,
connecting at their apex with the ventricle. The bases are attached
to the walls of the pericardial cavity, and are about equal in length to
the ventricle.

The pyramidal shape of the auricle is seen only when the ventricle
is pushed to one side. Naturally the auricles lie close to the side of
~ the ventricle, and when that organ is expanded are almost entirely
concealed. The auricles contract, forcing the blood into the ventricle,
when the ventricle contracts, the valve (PI. 9, fig. 3) connecting the
auricles and ventricle closes, and the blood is forced through the
aorte.

THE GILLS.
(Plates 7%, 10.)

The gills are four in number, one outer and one inner gill on each
side of the body. Each gill consists of two lamine, united along their
ventral edge, separated along their dorsal edge. The dorsal edge is es-
sentially straight, the anterior, ventral, and posterior edges follow the
curvature of the margin of the shell. The length of the gill is a little
more than two-thirds the length of the shell; the width bears about
the same proportion to the height of the shell, the length of the gill
being a little less than three times the width. The outer gills are
slightly larger and capable of greater extension than the inner gills.
The anterior portion of the gills is situated at a distance, equal to one-
fourth the length of the shell, from the anterior margin.

Their manner of attachment is as follows. The outer lamine of the
outer gills are attached to the interior of the mantle a short distance
from the dorsal portion, just below the pericardial space. They con-
tinue attached until within a short distance of the posterior extremity.

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 183

The inner Jamina of the outer gill and the outer lamina of the inner
gill are attached. ‘The inner lamina of the inner gill are at the an-
terior portion attached to the foot, but soon become free and remain
so for about one-half their length; back of the adductor muscle they are
united, and the dorsal part of the gills form a partial floor across
the space between the two lobes of the mantle, separating that space
into the branchial and epibranchial chambers. The two lamine of
each gill are united by their plates. There are about sixteen of these
plates in the space of five millimetres.

It is in the spaces or pockets formed by these plates and the laminee
of the gills, in the outer gills, that the young of the Anodonta remain
after being expelled from the ovaries, until they arrive at a certain
stage of development. The outer gills when filled with young are very
much distended, the thickness being several millimetres. The form of
the young shells can be distinguished only by the aid of a lens, and
in their form they differ so much from the parent, that to a person
who had not read a description of or critically studied them, their true
character would not be apparent.

The outer face of each lamina is composed of flat plates (PI. 7, fig.
1, g. p.) supported or rendered firm by chitinous rods (Pl. 7, fig. 1, ch.),
cylindrical in shape, two rods in each plate. Apparently these rods
are short, regularly arranged in pairs, with a short space between each
pair without rods, but on close examination, they will be seen to be con-
tinuous though at regular distances very slender. The edges of these
plates have large cilia (Pl. 7, fig. 1, ci.), which keep up a constant
motion. These plates support on one side a mesh-work of capil-
laries (Pl. 7, fig. 2), arranged in bands, the space between each band
equal to the width of the band. The gills possess nerves which will
be described under the head of the nervous system.

MUSCULAR SYSTEM.
(Plate 8.)

The principal muscles are the anterior and posterior adductors, the
anterior and posterior retractors, and the protractor pedis; in addition
to these there are two small muscles near the umbo, and small muscles
along the pallial line.

The anterior and posterior muscles are cylindrical bundles of fibres,
which pass transversely from one valve to the other, and serve to keep
the valves closed, antagonizing the action of the ligament. Whenever
from the will of the animal or from any cause the muscles of the
animal are relaxed, the valves open by the action of the ligament.

The anterior adductor (PI. 8, a.a.), issituated near the anterior mar-

184 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

gin, the base a little above a median line; it is oval in shape, about
one-third longer than wide.

The posterior adductor (Pl. 8, p.a.) muscle is situated on a line with
the anterior, a little more distant from the posterior margin than the
anterior muscle is from the anterior margin ; it is one and two-thirds
larger than the anterior muscle, about one-third longer than wide.
The protractor pedis muscle is situated just posterior to the base of
the anterior adductor muscle (Pl. 8, p.p.); it is fan-shaped in appear-
ance, spreading over a large portion of the body and foot (PI. 5, fig. 2,
p-p.), very near the surface. If the body is scraped gently with a
knife the strong muscular fibres will be immediately seen. This mus-
cle acts in opposition to the anterior and posterior retractor.

The anterior retractor muscle (Pl. 8, fig. 1, a. r.) has its origin just
posteriorly to the upper part of the anterior adductor muscle. The
impression made by the attachment of the muscle to the shell being
about one-third the size of that of the anterior adductor. The greater
portion of the fibres of this muscle pass downward toward the ven-
tral and anterior margin of the foot, having their greatest develop-
ment in the anterior portion, but some of the fibres pass upward, over
and through the substance of the liver. The fibres are for the most part
more deeply imbedded than either the protractor pedis or posterior re-
tractor fibres.

The posterior retractor muscles have their origin just anterior to
the upper portion of the posterior adductor (Pl. 8, fig. 3, p.r.). The
impression made by the attachment of this muscle to the shell is about
one-eighth the size of that of the posterior adductor muscle. It is at
first a muscular stem, but soon spreads, continuing through the lower ~
portion of the body and the foot, finding its greatest development in
the foot. Some of the fibres pass among those of the protractor
pedis, but as a rule they are beneath them.

At a short distance from the ventral margin the mantle is attached
to the shell by numerous small muscles along a line essentially parallel
with the margin of the shell; the impression of these muscles form-
ing the pallial line. Their fibres extend to the ventral margin of the
mantle, composing a large portion of that part of the mantle.

If a portion of the muscle is examined under the microscope it will
be seen that the fibres are composed of spindle-shaped bands (Pl. 4,
fig. 9), each of which contains an elongated nucleus. The space
around the nucleus is clear, but the rest of the band contains a great
number of granules, arranged in somewhat indistinct transverse rows.

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 185

THE NERVOUS SYSTEM.
(Plates 9, 12, 13.)

The nervous system consists of nerve centers or ganglia, connected
by nerves designated commissural cords or commissures, and nerves
proceeding from the nerve centers to different portions of the body,
and known as peripheral nerves.

The nerve ganglia are designated as the anterior or cerebral, the
pedal, and the posterior or parieto-splanchnic —a compound word
derived from the Latin paretes, a wall, and onlayyvor, the intes-
tine —and are so named because nerves of the mantle in part, the
gills and of the viscera, were supposed to proceed from this ganglion ;
but the pedal ganglia furnish the nerves of the viscera, and the cere-
bral ganglia furnish nerves to a large portion of the mantle. The
name being both unwieldy and calculated to mislead, I shall use the
term posterior both as being simpler and precisely defining the posts
tion of the ganglion.

On Plate 9 is a figure showing the nerves in position, on Plate 13
the nerve centers enlarged, and on Plate 12 the nerves dissected out
and enlarged twice. The same letters apply to each of the plates.
The different nerves will, however, be more clearly distinguished on
Plate 12.

The anterior or cerebral ganglia (Pl. 9, 12, 13, c. g.) are two in number,
and are situated one on each side of the animal, just back of the
lower portion of the anterior adductor muscle and between that mus-
cle and the protractor pedis, very near the surface, so that when the
shell is opened by cutting the muscles close to the shell, the ganglia
are generally exposed. They are wider than thick. The anterior por-
tion being the widest, graduaily narrowing to the posterior portion,
which is about two-thirds the width of the anterior; the length is a
little more than the width of the anterior portion. The measurements
in one specimen are as follows: width of anterior portion, one
millimetre ; posterior portion, two-thirds of one millimetre; length,
one and one-half millimetres ; thickness, a little less than two-thirds
of one millimetre. On account of the two nerves proceeding from
the upper portion, and the two from the lower portion, the ganglion
presents an indistinct bilobate appearance.

From the upper angle of the anterior portion (PI. 9, 12, 13, c. ¢.)
a commissural cord proceeds forward and upward, encircling the
cesophagus and connecting with the cerebral ganglion of the opposite
side. From the lower angle of the anterior portion (Pl. 9, 12, 13,
a. a. 0.) a peripheral nerve passes directly forward into the anterior ad-

[Sen. Doc. No. 38. ] 24

186 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

ductor muscle, bifurcating when about half way through the muscle,
and giving forth numerous filaments: from the lower part of the pos-
terior portion a commissural cord proceeds, continuing to the upper
portion of the animal, just below the generative orifice, thence through
the glandular portion of the renal organ. Through the renal organ
the cords from the cerebral ganglia, that is, one from each ganglion,
are parallel and nearly contiguous to each other (PI. 12,0. b.n.) until
they approach the tendons of the posterior retractor muscles, when
they separate, passing over the exterior of the tendons, then rapidly ap-
proaching each other, and uniting with the posterior ganglion (PI.
9512; 13) pi ‘ss 2):

From the upper angle of the posterior portion of the cerebral gang-
lion a commissural cord passes dorsally and posteriorly, for a short
distance, nearly parallel with the commissural cord uniting the an-
terior and posterior ganglia (Pl. 12, p.e.c.; Pl. 13, fig. 2, p.e.¢.); then
turning toward the posterior and ventral portion, it passes through the
substance of the liver, below the stomach, and unites with the pedal
ganglia (Pl. 9, 12, p. g.). Sometimes branching from the nerve of the
anterior,adductor muscle, at other times proceeding directly from the
ganglion just posterior to the insertion of that nerve, there is a somewhat
finer one, which continues forward into the anterior portion of the
mantle (Pl. 9, 12, a. m. n.). A peripheral nerve: proceeds from the
under side of the ganglion, about midway between the ends, and passes
almost directly downward into the mantle (Pl. 9, 12, a. m. n.) bifurcating
at a short distance from the ganglion — one branch continuing nearly
directly downward, the other continuing toward the posterior portion,
giving off several branches to the thickened muscular border of the
mantle, continuing apparent to the unaided eye, for a distance of a lit-
tle less than one-half the length of the mantle.

The pedal ganglia (Pl. 9, 12, p. g.) are situated in the body, about one-
fourth of its length from the anterior margin, thus being a little
posterior to the cerebral ganglia, and about one centimetre distant from
them, situated midway between the sides of the body; they consist of
two elongate oval bodies, which are joined to each other for about
one-half their length, which is a little less than three millimetres;
width, one millimetre. Their natural position is at an angle of forty-
five degrees to a vertical line through the body. From the upper end
proceeds the commissural cord connecting the cerebral and pedal
ganglia (Pl. 9.12, p. e.¢.). From the lower end proceeds a peripheral
nerve (PI. 9,12, p.h. n.), which continues on a line with the ganglion,
having frequent branches, to one of which is attached the auditory
organ (Pl. 9, 12. au. s.). From just beneath this nerve another nerve
proceeds, having the same general direction, but smaller. A little an-

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 187

terior to the first-mentioned nerve is another nerve which bifurcates
at a short distance from the ganglion, and continues in the muscular
strata of the foot at an angle of ten degrees to the first-mentioned
nerve; from this nerve, and also from the others described, proceed
numerous filaments. From a point about midway between the ends
proceeds another nerve, which continues almost directly toward the
ventral margin among the muscular fibres; about midway between
this nerve and the commissural cord is another nerve (PI. 9, 12, an.),
which continues directly toward the anterior portion of the animal,
among the muscular fibres, bifurcating at a short distance from the
ganglia. From the middle of the dorsal portion (Pl. 9, 12, m. n.) a
nerve proceeds, continuing posteriorly at right angles to the length of
the ganglion. The nerve proceeding from the pedal ganglia furnishes
nerves to the muscles of the body and foot, and to the viscera.

The posterior ganglia (Pl. 9, 12, p.s. g.) are situated immediately
below the posterior adductor muscle, and are so closely apposed
as to present the appearance of a single bilobate ganglion, The
bilobate appearance is more apparent than that of the cerebral
ganglia, but they are much more closely united than the pedal gang-
lia; each ganglion is two millimetres long and one and one-half mulli-
metres wide, and the inner margin is joined to its fellow throughout the
entire length. From the anterior portion proceed the commissural cords
(Pl. 9,12, p. s. ¢.), connecting the posterior and cerebral ganglia.
From the anterior angles of the ganglia (Pl. 9, 12, g. n.) proceeds a
peripheral nerve, which for a short distance continues parallel with
the commissural cord, then curving away from that cord turns quite
abruptly backward, continuing along the junction of the exterior
lamelle of the inner gills and the inner lamelle of the outer gills,
branches entering the gills. From the posterior portion of the gang-
lia a very large nerve takes its origin, the diameter of which is equal
to three times the diameter of the commissural cord. (PI. 9,12, p. n.)
This nerve at first continues directly toward the posterior portion of the
animal, branching at the distance of about seven millimetres from
the ganglia (PI. 9,12, p.m.n.). The branch entering the mantle
is first directed toward the ventral portion, gradually curving and
becoming parallel with the ventral portion, and having frequent
branches, which continue into the muscular portion of the mantle.
This nerve is slightly smaller than the commissural cord, Almost im-
mediately after this branch leaves the large nerve, that nerve again
branches, the larger portion continuing toward the rudimentary
branchial siphon, and its branches supplying that portion of the man-
tle with nerves (Pl. 9,12,b.n.). Likewise the smaller portion proceeds
toward the rudimentary exhalent siphon. In addition to these princi-

188 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

pal nerves, there are other small nerve filaments supplying the differ-
ent organs of that portion of the animal with nerves.

The auditory organ consists of a sac attached to one of the
branches of the nerve proceeding from the lower end of the pedal
ganglion, is filled with colorless fluid, and contains a hard body called
the otolith, which is covered with cilia and keeps up a constant
rotary motion.

The sense of touch appears to be very acute, more especially in
the foot proper ; the slightest touch, when the foot isexpanded, causing
it to contract immediately.

Though possessed of an organ of hearing and without organs of
sight, as far as our present knowledge extends, the Anodonta is much
more sensitive to light than to sound. I have kept a large number in
a tank for several months, and have thus had a good opportunity to
judge of the effects of sound and Jight, and from the observations and
experiments I have made, it seems certain that they are not affected by
any sound which does not communicate a visible jar to the water.

That they are sensitive to light is shown by the fact that on bright
days the rudimentary siphons are more fully expanded, and the inha-
lant and exhalant currents much stronger than on cloudy days or at
night ; at which times the shell is generally closed.

The use of the tentacles surrounding the inhalent siphon has not
been satisfactorily determined. It is possible that they will prove to
be organs of sight. It seems impossible that animals so sensitive to
light should be without special organs of vision.

CIRCULATORY SYSTEM.

The blood of the Anodonta is colorless. The corpuscles are simi-
lar in form and structure to colorless blood corpuscles of man, and
haye the same continually changing movements. Owing to the
soft jelly-like nature of the animal substance, it is extremely difficult
to determine with accuracy many points in relation to the circulation.

From the ventricle of the heart proceed two aortz (from the Greek
word aoptn the heart), a name applied only to the arteries which pro-
ceed directly from the heart. The anterior aorta (Pl. 10, a. ao.) enters
the body above and in close contiguity to the intestinal canal, bending
slightly to the right, turning downward and a little posteriorly, one
branch entering the mantle: just behind the anterior adductor
muscle a large branch goes downward and runs parallel with the mar-
gin of the foot, between the muscular portion of the foot and the body
proper, sending numerous branches down to the ventral margin of the
foot. Immediately after this branch leaves the main artery it sends out
a branch to the anterior adductor muscle, mouth, and other anterior

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 189

portions of the body; the main artery continues posteriorly, dividing
into three large branches, continuing over and between the folds of the
intestine. ‘The posterior aorta (Pl. 10, p. ao.), leaves the ventricle be-
low the rectum, and just before reaching the posterior adductor mus-
cle it bifurcates, and sends branches to the posterior adductor muscle,
to the pericardium, and to the rectum. The larger branch passes
over the posterior adductor muscle entering the mantle, and con-
tinues in the thickened portion of the mantle below the pallial line
until it meets the branch from the anterior aorta. The blood is
returned in the body by innumerable small veins, gradually growing
larger toward the vena-cava. Fora short distance before leaving
the body there is a large sinus which is formed by the union of
the larger veins, these connecting with the innumerable small veins ;
this sinus connects With a cavity situated beneath and between the two
portions of the renal organ, which is known as the vena-cava, which
connects with veins and capillaries of the gills. By the contraction of
the ventricle the blood is forced through the anterior and posterior
aortz to the extremities, and is returned by the veins to the vena-cava ;
it then passes through the tissues of the glandular sac of the renai
organ ; it there loses its urea; the renal organ performing the same
office as the kidneys of vertebrated animals, thence passing through
the gills, and in the gills through a fine net-work of capillaries, and by
contact with the air in the water becoming oxygenated, the gills per-
forming the same functions as the lungs of vertebrated animals. ‘The
blood circulating through the thin portion of the mantle also becomes
oxygenated to a certain extent, the action of the capillaries of the gills
being supplemented by those of the mantle ; from the capillaries of the
gills the blood returns to the auricles and from them to the ventricle.
The body sinus connects with the vena-cava by an oval opening, which
is covered by a projection from the anterior side, which is held in
place by a muscular cord; this arrangement of the valve permits the
flow of blood from the sinus to the vena-cava, but effectually prevents
any return. ‘The auricles are connected with the ventricle by an oval
opening; the “lips” of this orifice are very thin and extend into the
ventricles (Pl. 8, fig. 4), they are in shape like a sack, with both ends
open. At the orifice they are kept apart by their attachment to the
margins of the orifice, but as they recede the two margins fall together.
When the auricle contracts, the blood easily passes through this valve,
but when the ventricle contracts, the margins fall together, preventing
the return of the blood to the auricles and causing it to be forced
through the aorte.

The pericardium has direct communication, both with the blood sys-
tem and also with the branchial chamber, and thus contains a mix-
ture of blood and water.

190 THIRTY-FIFTH REPORT ON THE STATE MUSEUM.

The non-glandular sac of the renal organ connects with the
branchial chamber, is filled with water and carries off the waste pro-
duct separated from the blood by the action of the glandular sac.

SEX AND REPRODUCTION.

Formerly the Anodonta was considered to be androgynous or uni-
sexual, that is, the male and female organs combined in one animal.
Leeuwenhoek, in 1702, maintained that they were bisexual, though
afterward changing his opinion, ‘The former view is now accepted
by nearly all writers on the subject, though it is still maintained by some
that they are unisexual. The fact that the organs of generation in
all individuals are very similar, and as far as my observation goes, dur-
ing the breeding season fully nine-tenths of the animals have their gills
distended with young, gives some plausibility to that belief, for if the
animals are bisexual, we would naturally expect to find the sexes
in about equal proportions. Itis claimed also that from the greater
room required by the female in the shell, owing to the distension of the
gills with the young, that the shells of that sex are more gibbous than
those of the male, but so far as Anodonta fluviatilis is concerned, that
belief is an error, though undoubtedly true in regard to some
species of Unio. Among the few Anodonta found by me, the gills of
which did not contain young, were some, the gibbosity of which was
so great that the thickness was nearly equal tc the height, while among
those, the gills of which did contain young, were some quite flat, the
thickness scarcely exceeding one-fourth the height. That some of the
animals were without young does not weaken the force of the argu-
ment of those believing in unisexuality, for even if the animals were
hermaphroditic, from various causes there would, in all probability,
be some without young. It seems to me that the simplest way to set-
tle the matter would be, not microscopic investigations, but to collect
large numbers at the time when the gills of the females are distended
with young, if half or even one-third were without young it would nearly
prove the bisexual view to be right; on the other hand, if nearly all
were with young, the opposite would be proved. For certainly in order
to fertilize the individuals in a pond or river, the males should be in con-
siderable numbers. The generative organs, testes and ovaries consist of
racemose glands, situated on each side of the subhepatic region of the
body, the external openings of which are near the attachment of the
inner gill to the body by the side of the openings of the pleural sac of
the renal organ. The egg is globular and transparent. The sperma-
tozoa are short rod-like bodies, with an active cilium. The yolk of the
egg is prolonged into ashort tube with open end, through which
(according to Barry) the spermatozoa enter. The ova pass out of

ANATOMY AND PHYSIOLOGY OF ANODONTA FLUVIATILIS. 191

the generative opening during the latter part of summer, passing into
the cavity formed by the two lamellze of the outer gills, and there re-
main until the following spring, when they are sufficiently developed
to leave the protection of the parent.

The yolk divides into two portions, nearly, but not quite, separating.
The valves are connected by a hinge; near the hinge line is an
adductor muscle, which by its frequent contractions gives a flapping
motion to the valves; in the angle formed by the junction of the two
valves is ashort hollow tube, from which is produced a long filament
known as a byssus; the valves are slightly convex-trigoual in outline,
presenting very much the appearance of a shield (Pl. 4, fig. 2), in no
respect resembling the adult shell. The apex is prolonged into aser-
rated spine at right angles to the shell, the teeth or serrations are on the
upper portion of the spine and are in two rows. After the valves have
become definitely closed by the action of the adductor muscle, the
halves are blended together, the gills are developed, the foot grows, the
form of the shell changes, and the young Anodonta becomes like the
parent in every respect except size.

; a ris ak
man

Cae &
es = 4

a. Md.
p. a.
v. m.

dp:

Anterior margin.
Posterior margin.
Ventral margin.
Dorsal portion.

PLATE III.

Exterior of shell.
lig. Ligament.
f. Foot, extended.

umb. Umbo.
h. Hinge-line.

a S
"CE ISTH FON SUL OTE}
=) Rd

I

i =
py ' 1) «ae
7

“—- ; dg eae ant >

: ware Lon). Pe ait nc pei cate. 7 :

_ vis “ene Ball ah 4 a ss 7 . : eee: fan aa
oes “i ite so! ton wk r an NA sia Are

_
ta hue te eiaee wr ee Se NaS igi bp wa

3
te

: _ 7 = ya: sulky fan ntinne note eee ) ae i Le

ity moo
cee arate at iene

<—* = Eis ugh a daub ay a Cae
et Wie aan epee . Py da yd ee a tig
¥. : “0 » ie

= | ie

7 ae > : ; 7 :
79 mai ee _

iG atl
on Beets Hiiicok nk ae Ae of x ol

usa t het ot ost = V :

... aie oe

tit v4 aa. Ae fat
sig Ee Ps on enti hae, 8 ry 7 a ie Nes : 4 : a rein 6 a
a i 7 ae e - - 7 . 2 gt i. rae iy are wes sant Ae ace Pat es

niente

o. feet aft He-miylu: pial sfioias he seit i
ea) : Nak ae Re et ee D a
sll ee ie pie heath eA SANE mits. : _
2 ca : ebb fteealle atin fete LS Gua ime ie

; es am _ zt. ue atlas Pagel Naas te ons. ~~ PG

Be. + <3 ey saul la’ ~
eee te

is

a ae

ae -

a
as

2
.

ep.

pr.

PLATE IV.

Fie. 1 — Exterior of shell, dorsal view.

. Anterior portion. lig. Ligament.
. Posterior portion. l. v. Left valve.
. Dorsal portion. r. v. Right valve.
Fic. 2— Young shell before leaving the gills.
. Valves. by. Byssus.
. Hinge-line. c. Cilia.
. The animal. s. Serrated spines.
Fie. 8 — Epidermis.
. Pigment cells.

Fic. 4— Prismatic layer, transverse section.
Fie. 5 — Narceous layer, transverse section.
Fie. 6 — Section of the shell.
Epidermis. nac, Nacreous layer.
Prismatic layer.
Fic. 7 — Enlargement of secreting tubes of the liver.
Fic. 8-— Parasite frequently found on the animal.

Fic. 9 — Enlargement of tentacles of the branchial siphon.

Fie. 10 — Enlargement of muscular fibres.
Fre. 11-— Mass-of-the tubules of-the-lver.
Frer-i2 > Young Anodonta.

Phil Ast hth

Plate +

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' 2 :
% ay
'
.
4
'
ht
Pd ;
: 7 i

mf
ero

ae ns ,
av ee fone aac

saat ee i
ae ae eos a
ie ier tet
aa on fare

a
a 7
= ©
s'y

¥

5
a
a
a) oe Ne

oR i i> _ - on fF Cee :

Pt ae oe 7 he: 4 a) a 4 Ne ; Larne 7

. , Ver - Ut - ae 7 ad

mele

me Mi
=. |
rs

i
att

y ; 7 : : aver. -) .
* =a ite i ee ; a ee ad
4 -

. * pbleaensb ty ip Lidia Pant Aone te

ert a
ae peers pvtit ae a ® “Bin. eet t nea
» oaltouliyts fib! aisal, . e ae - zi ie ap 5 = :

oliyn RONEN aA Miss 57? suneed
43 piu oon neice oe Oh ae ‘a 490"
Be pit: Dion 24, tg atl npg: ae atta sit int
= os we hee ee hoe ea. aaa nae 4
2] ‘Tete if re Nie Oe he Shae en Ph ol
Lattin Wegner ee sin ext Mea ak ee
oe 8 co Re ihe seer b al oyion witagit yg BMT, nti at if
seater, ete ae es ate

PLATE V.

Fie. 1 — Showing blood vessels of the mantle.

. Anterior adductor muscle. i, s, Inhalent siphon.

. Anterior retractor muscle, e. s. Exhalent siphon,

. Protractor pedis muscle. p. a. Posterior adductor muscle,
- Foot. p-r. Posterior retractor muscle,
. Anterior mantle nerve. 0. b, Organ of Bojanus, or renal
. Pallial line. organ.

. Gill. au. Auricles.

- Muscular fibres, ~ v. Ventricle.

. Posterior mantle nerve ve. Veins.

i fAueqiy i}®) y Swos Teq psa AYU SV Ted

¢ e}e
Sot Sch ‘GE ISTH TEN SUV eye}

SUTCUIAVILAN OVS Wb tor

nar
Ye
bet?
7

PI

Ka:

a
e

oe

“we i

© 7 .
too a. oe =, ao Pine
a, Ta > a. - h

ae poe i> fae

Ne ATOR ie

ftp aoe

rg eee ee

loge ti
al mae

‘

na
We

a

oF

ple

PLATE VI.

Fre. 1 — The animal is dissected to show the intestinal ‘canal.

a. Anterior adductor muscle. Vv.
m. Mouth. p.
f. Foot. au.
g. Gill. real
t. Tentacles of inhalent siphon. i. ¢, i. ¢,
ec. Branchial chamber.

c. Cloacal chamber. x
a. Anus. if
a. Posterior adductor muscle. Ih
r. Posterior retractor muscle.

Ventricle.

Pericardium.

Auricle.

Intestinal canal.

Points of attachment of in-
testine.

Rectum.

Liver.

Stomach.

ite

c

—

OD:

i debt

Var

e Mus N

tat

S

2

ren
HUD GUL

Pitrata rec
Faria vrai TM
i feavdc HHA vA KSI
irinnrararess
Barry
ANsAN seb ehdees
HEISE Hi TEs tak
Pian
ne

IME Terr reer Yen
OUAAGSS iA t4 fo Ab pated eg pdehane LALA CL
IH aks Cia 484 LA HALLE COG HA TAL Rg eb skh
Ai jMLesEL aN SHINE does c iss Lead A OED
Weer rrrerrni rere
Maurin
Mapa 3
LI UGGS np eds Hf ASRS AU AIA 416 6 AA
Ag nisadbed Las parca see4e NALIUSL AL SbUR phe base oe
ners ane
Aires: ‘
PEM NEAL aac katt aisea Shas FAA AALAN (spades NEL GOES
EY s4 1A b esr ven s74h yrtanwege) HNN OE ESA PEELE LL
ee Asn IMIG ws igs UENIABAY HAL
PH Fay Atawea iA nay ANSEL GA
AERIS ED ALE

Mesa EHO L EEC ES

SENT ASEH ARON Sieg (qo ca LIAN
Fy AYELAC SETA CHALE TEL MLAL Cat
Hiuuasseey y Hebe (Ast gE ES
Mi lasay pie
Ans Fas Af Maas OP Winter yy
PnPPren ince Mere reer iey rT aa be
Leena g eh AiO TE a ape bideeaRerag
initge ed pana nasseSRL HALAS Spb
Tt EOE OA hes
on rer riper Ce
TUT: Iie eeea eres ee tala Peiildebes
wea tenente Dips ALS ed sbapepaay 45656 ek og ED
Patient ree rece en Tey

Daten

v4,
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HU eatel babes Ee

Hons iAlisdany SE AshuAiHOAAAUD EAE EES AE
vhs rH Cee bes ea sy hassHi STULL Ee Bo Ek Day
APRTME ASE Sos urs AES LEE E
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Cenncnin
Drreni
PENGUIN
orn
i bidag

PLATE VIL:

Fic. 1 — Enlargement of outer surface of gill.
g. p. Gill plates. c. i. Cilia.
ch. Chitinous rods. :
Fic. 2.— Enlargement of capillaries of gills.
Fic. 3.— Enlargement of veins of mantle.
Fic. 4.— Showing specimen with mantle removed.

a. a. Anterior adductor muscle. r. Rectum.
a, r. Anterior retractor muscle. a, Anus.
p. p. Protractor pedis muscle. p. a. Posterior adductor.
m. Mouth. p. r. Posterior retractor.
1. p. Labial palpi. p. Pericardium.
f, Foot. v. Ventricle.
b. c. Branchial chamber. au. Auricle.
t. Tentacles of inhalent-siphon. m. Mantle.
c. c. Cloacal chamber. g. Gill.

Fie 5.— Showing the mantle and gills thrown back exposing the foot, body
and labial palpi.

m. Mantle. o. g. Outer gill.

mo. Mouth. b. c. Branchial cavity.

1. p. Labial palpi. t. Tentacles of inhalent siphon.
f. Foot. op. Opening through the gill for
b. Body. passage of the body.

i, g. Inner gill.

ANDDONTA TinowisINio bites

State Mus Nat. Hist.35.

Pilater/

WTVUSTN ELE
TTT NTH

yluli IVVUTRTVTUTITITTIIUIUNCTRUUIUIIU UPR CLA LLeLOLLO CL LORAonneatas

Plagl Ast Lith.

Weed Parsons & Co Albany, NY .

at 2 ey
ain, dys ou:
or : te bag

he _ = : nats 7 aa 7 ; 7 rT, - 7s _ |

a ible spin ies hy Feely = ok ee
-. ay > i. 7 dy m2 wear Layee Cie) :

_ - ican a >. 4 ees 9 PG evn cas ve: pi) z a ee a 7

: he lami 7 sip et ee

Tats ar Sirabaneneet — 7 , cS i} -

a aa! Per M e! pie i, ce 7) ae
fe na aN bs Sis ba x aM Hint % Pes |
it y meee a oe

ial
= AW.
RSs

r a

,

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a ae ‘ Lith tie

f eae aw “os

S
ee

Nt’, Rete - Dee,’ i Son Ly as Ly
oe 7 . i : >t nie :
ae “ cee she Up tee aes fe:

iw Be

PLATE VIII.

Showing the muscles of the foot and body.

The same letters apply to the same organs on each of the figures.
Fies. 1, 2, 3.

a, a. Anterior adductor muscle. g. Gills.

a. ry. Anterior retractor muscle. p- Pericardium.
p. a. Posterior adductor muscle. au. Auricle.

p. r. Posterior retractor muscle. v. Ventricle.

p. p. Protractor pedis muscle.

Plate 8

in
AA

State Mus Nat.Mist

ty a, Ny, fi
Aypasie Cygne

Aly ae? | i 2. ee , Py i ee 7 ans nF he > Rote.
ie Lhe ae oe on i 4 roar - ~~ i, > i = naa st re ig a Pai hy Awa. tala TF a” A ice 17 i va
. ae biel vrs FP iy ae . a wan DY i ri ee we ee me! ae Ge Pre i”
es a. “Gea, : a i —* ee _s in an a! - tan in | . 4 vs... ae oats r ayy “ort un.
ae a S Aa as a a ris pes ’ i>’ lee : ryote Save a
cs 7 eee Sein? - a ~ a a oe cae 0 ~ a. a ~ ae te a ay my «73 are \ ,. wm
a - —_ = a ee 7 7 ¥ >
” ves eee <i a ‘ ip ic ae ey ec bit ol ae a Seen mc
Ve Wee eel 7 Rt tne ond a r } -: aod : »

=. » i Ce th > eee ‘a ee ate 7 eS tag De 7 ie a ia

vy EE LS a er Te tN) ce
Y eee i! = - : P De ie aw Se tk & = o eS a
Poy ae saa Teel aay Chen Lar AE ee ag > Se ee Pee
ia aa as : i oe m4 _ a te . oe L ~~ Dina . 7 : On, Yee _
9 A eee el cS) eae Nae [= * 4) “Ses > eee

+a eb i ay! 7 ai ae esl a iy *g — cas if be 7s am [eet a
Si ia hoot gue, OT ing ES a ay 2 an yo -~he ots
Etim ect 6 TP A 6 ey ee
“ad a, on es, ee Ww eta? ON y _ ir ees ve. =~ — > > So
7 io ie , Js: ~ 7, 7 Py ee A) h “2 ns el aS 7 ’ 24a. ee a
es <a “OYA : ra & EB. : i a nD _ Le : 7 : 7 _ ier f » cole _——_ ey
MS (3 os ) 2 Myr ed: Se = te ae
SS eae - “vy beads ws 7 ae 7 v2 ay — Sea is 1) c= 7 + Fe oe

Be eel. 68-954 4 rae ¥y nee re ae “ore
7 oes 8 ca © 7 Da: —y ee * a ae a va wy UA _ —_— \-) 3 Me: Ane
CRP Cty aya! yy ee

ni f > oe BRR, a = ae 7 - T 7 . fhe ba 4M wet _- “18 F te - 0 _—s oy.

I Fe Bae A cee “ae
7 me: i = rep vy. a on - A Bi 7 ~~“ ag & ue

ae “a3 ae iq = Hyiveiiyy: yt ie oe i633 Basen ree pias ts ira a

Ce. ee 7 (A. yy. on 7
(ok) ts 7 ; an Aleiaite i), ra nf ORR val bahia at 4a, Ui caite 2 iz eon
ie a s cs ‘ion uae ae Betting uh Pade gs eae
at 2 is ea ¢ <2 ‘ada stan: in ‘Ti A ea 7 lel) en. i 4 i
: ao ey oor as nee A «Vin a reat yg wie og
: . &;
u Bae tae einen sn i using ay tnt Labia : as aA ee :

" ; *)
ea was. av ieee”? - ey > Neo é aol dado i, _ ae mir ia rT .

ae 7 sil), : “8 = a “ 8 -
a we Sa aatelt hs ik’ - oor hgh val ey
i rs haere uaa tye Ty suas i ry ~~ Sonik , _%
7 i. a a - n 4 tr) ae 7 + : 7
an Pi 4a,” &* jeg + oo heh Hi pasa sr |e
a " an aves paaily Pe lilanas! paabsts Agius pivane whe. 4 c ome \) \ ae ,
a su . a i: ads > sited tn <— ” ?. = os : F re ie hy Ane sc 2
7 ' A ig a aan i in _— - A he : 7 Plaats sai) Di i 7 : - é
S meet ee ‘a . Peo une Fatite PA area Sy ant 7 ¥ , an 7
ae ae Fi ag aad wat pun Aut (te ie =" oe : ard Veet eile = i ry
—— - % ated ity Pea ti Biited® api on - ee 1! ar a _ oh 7
* : ve ond ° 7 a ah ls ae th _ D te. —_— 1 - - atu oat Hah _ ' 7
¥ eee : a4 Vio. __ ile is yids ale: My {irine iets 7 ae - 7 ‘i a en thee aa lee ul ay ix 7 _
ee ee 7 ae mem ude my) iy: ‘, i pede Ns Ay, ;
ae ea <« ar sips fish hs gute gg Reuse a <7 “poet Ora + f eM
p ¢ mn & vo = = ¥ 7 ? ere wn ale
ae st ek ana Pereira Lp ah. tr | ips wu iid aay i es y
a We r- > =. A i = te, oun efile : he caus it oyu Bs wa i Oe ‘ a.
es = Fae ¥ 7 a @ pale ae : ae - - a my RAN ial i?
ms : aoa... ' }
ns we ‘gins Lome a ee ae ae ue pourglnnen hei ts aA at i
,.. i — Kos Aulljoss 7 LAs -¢

7 a
Belithi As 1 wet vit kin 4 iin gelaiiniatead: RA Le tates
ee A ae pate) tity ban as ‘ iat fi) i Nyt tates bert A

r OMe Ls aly tag iyi
es Ws ie aoly “— 2 f ‘ae vik le Le ay
an Py fins rigs de 8 Ae aioe aii 5 Alp ni een, aa :
ee ,

Ls ee ae yar pees wee) ee Apt ay Ae
Ss ty Be eet, oe das seam Way HA rae yl sit aan | : ae ©. iT a 7 2"
i an ea isa ¢: ros A ee Sp Res Jou plandoie fr, 9 0

. ~

a .- ts jaa a rt pani tou SEEN ‘Vi Sige ant Anal Mv ik Uh pans ray a)
= A ’ i

at ee usta ina Tah. i ats Hat peda) earl, ey
aS ian ue oe ated mia” epee aa :

; rte —
im - » Ae Nae oi a Bint ar erat: eR ies = fy ‘“ > Th ha ey Ge * 3)

eek a8 pending thweutipay ap 4): fall Latha SEF! ROT SDMA MesNatiR Me aah se 2
ee hal eee Wey pik ae ee pera pul Nol : :
ao een bs x SY RAT NaS 6 aot “i is ue Faye Lebains a ia A
* oe fe) <5 es ae vp } >< =
” a bs + any |. = - a 7 ry - ay! aap. ta a a
7 aa :>,. a : ra Lp © 7 ra : 4, \ ie 1.0 7 ee f
' ae RS ee a aes) 4 ie A PT) a ‘
/ 7 a ey 2 a - Ds - ae — Wr
~ ate ae itm a Vi >) <i A i,
os ee bat rm en o =e - oe
mi. Saen a ae > oa a v as als iy - a —
eo de) + »_¢ Ss ek - 7 7 7
: ce ag M9 ae i m, Pea at
een is, « as : 7 7 7 ¥ a
NS NT i” th. 8 i
I ie eB ieee
mee Sy She <2 mt D6 Vise he . Sa Pen ie Tye 7 : od
eat rs or ie 4) _ : Cir as ps ; as ie =a Pain j ae oe v P
OS "Fae 0 ry oe
7 aT. >. a ee > Soo a vm Pa} vat pee |e eet spe :
Sigh oe ae as ee oe "Ln Sree
ee CP. ie ey a) i) = ee eg Oe ae a
™ & 7 te sas aes at ~ a ‘o 7 i hee ae he p
at ~ 49 : 2 ary 2) - - - a or ees ee ee he OE F]

PLATE IX.

Fie. 1.— A dorsal veiw of the pericardial cavity, mantle not removed.

p. a. Posterior adductor. au. Auricle.
r. Posterior retractor. v. Ventricle.
p. m. Mantle. p. Pericardium.

o. b. Organ of Bojanus.
Fie, 2.— A dorsal view of the pericardial cavity, mantle removed.

p. a. Posterior adductor. v.. Ventricle.
p.r. Posterior retractor. au. Auricle.
r. Rectum. o. b. Organ of Bojanus.

p- Pericardial cavity.
Fie. 3.— The valve leading from the auricle to the ventricle.
val. -Valve. .- au. Auricle.
v. Veutricle.
Fie. 4.— Organ of Bojanus or renal organ.

p. a. Posterior adductor. o. b. c. Opening leading from the
r. Rectum. non-glandular sac to the
a, Anus. branchial chamber.
p. r. Posterior retractor. n. g. s. Non-glandular sac.
p. Pericardial cavity. g. s. Glandular sac.
v. Ventricle: 0. €. Ss. Opening leading from the
0. p. g. Opening leading from the glandular to the non-glan-
floor of the pericardium to dular sac.
glandular sac. au. Auricle.

Fic. 5.— Floor of the pericardium, showing the 'two openings (o. p. g.) into
the renal organ.
. Fic. 6.—Floor of non-glandular sac, showing openings into the glandular
sac and branchial chamber, and the openings from the glandular
sac as shown in Fig. 5.
Fie. 7. Diagram showing more plainly than fig. 4 the passage leading from
the floor of the pericardium to the branchial chamber.

Fie. 8.— Showing nerves in place.

c. g. Cerebral ganglion. p. g. Pedal ganglion.

c. c. The commissural cord con- pe. c. Commissural cord connect-
necting the cerebral gang- ing the pedal and cerebral
lia. ganglia.

ps. g. Posterior ganglia. a.m.n. Anterior mantle nerve,

ps. c. Commissural cord ‘connect- g.n. The nerve whose branches
ing the cerebral and pos- are the nerves of the gills.

terior ganglia. p- m.n. Posterior mantle nerve.

Plate 9

State Mus Nat.

\

Weed,P.

L

foal Ast lith

—™

Li

cat

eh
i ory)

—

i

»

i

3

Verse bay leak Fe

PLATE X.

Showing the circulatory system as described in the text. The arteries
are represented by dark shading; the veins and large sinus connecting with
the vena cava by lighter shading; the intestinal canal and other parts will
be easily recognized by still lighter shading.

a. ao. Anterior aorta. ram. Ramifications of arteries.
p. ao. Posterior aorta. r. v. Ramifications of veins.
s. Sinus.

The larger veins and arteries only are represented here; to endeavor to rep-
resent more in so small a space would only confuse the student.

ate LO.

Jk

ARMY
SUA

“Ags
Pern
te NIST ea)
PTV

= } PAH en

eabid peed yy id pEsev cscs DUNNE EE

A U1 “CATE SVGL HALLE CLAS 20 OPTED TESST

\ a TTL Seuss HLTA LTLER I

ech SCLCUTEEYSEDRUCAE GSSSTE CHAE SS EDEEN OVO HE LE

i cseorven eeCUETALGENOaE Labaher NUE SHEA IMIREAE (IED Bee

SALOME SDS MOEN NESTA CLAY ROOT CERN pap) cL aE COOP A PERE HUME

SUTRAS SA ESMLETULS (19541 ppeg S28 RE a Egg Sta EEE Pes ae ELLE Ht

Try SUS a COVES AAV OF RS y cert ey be eA LE ND CUCL
Eu

.: a4nhy Cece
Ceemni rine inure,
SASMSEDE HSC nnAn} ots Phen bee:
eaneshgeetit aie eset ies
Serene
Merttreninint rcs
Wupberathasaniatsbereg 88>

Pieris

dears fs
%

State Mus Nat.Hist.3

5
iN m 9 iy a
POM

PLATE XI.

Fie. 1.— Interior of shell.

a. a.° Impression of anterior ad- p. r. Impression of posterior re-
ductor muscle. tractor muscle.
p. a. Impression of posterior ad- p. l. Impression of pallial line.
ductor muscle. m. f. Impression of umbonal mus-
a. r. Impression of anterior re- cles.
tractor muscle. p. 1. m. Pallial line muscles.
p-. p. Impression of protractor r. t. Rudimentary teeth.
pedis muscle. mar. Markings left by the adduc-

tor muscles.
Fia. 2.— Interior of shell of Unio complanatus.

a. a. Anterior adductor. p.r. Posterior retractor.
a. r. Anterior retractor. p. l. Pallial line.

p. p. Protractor pedis. c. t. Cardinal teeth.

p. a. Posterior adductor. lat. Lateral teeth.

Fig. 3.— The mantle thrown back, showing the labial palpi (1. p.) in position.
Fig. 4.— Transverse section.

sh. Shell. o. b. Organ of Bojanus.
m. Mantle. v. Ventricle.
o. g. Outer gill. au. Auricle.

i. g. Inner gill. p. Pericardium.
f. Foot. r. Rectum.

State Mus.Nat Hist 35 | (a eae Plate I

44 fb A Ad

Pha] Ast dith

Weed Parsons & Co Albany NY.

7, 4% -. oe a
Vea | cts Cm
er) ee ee

ai) ee ean ve a .

ae = 7 a 2.2 =) : : fo
7 tof >» i < ow ee = a Vd é ' ot ae a
: - ma ig. ee ne - a iy 2 S27 . + a Ai) ho mn
r 5 tre ae - a ca < P a ® iy at sy
ee a ee yl a5 ro — . 4 = S. Le» a pe —
=< tn ee ima - i ; YA, aa - :
a ee nat Pl he roa _
’ em Se ee : : <8 4 a,
Se Sx SN 6) We or” ara
=) a = = 4 — > ‘ee os in => 7
Se hes ak ie Be fo * 1.89 eee
et ee cy ras: a es ee
ie SS, [Sit ae <a > : a —_ eile Se 7 a
Dae aaa Se i ae aaa Ln alte : ; are a is LG ‘y ae a
al —_- Ye _ ta o_o a ia
eae i ese crea. : =! : . = . 10 ell et - oe
= i ee eee wa ® ao © i
ie ey oe = of i sah eo : 0 ee. ee
—% ot SS re nk OW oll — _ nas rar ae Se
me aa Ee 9 & wana > 1a oe 7 § 5 1 i :
ae" - ae iy ven a :
Said We
: , he oz ae ae
re = “Bea
+d i ae y _ ~~ ,* x ie
- a 7 o es ‘> pales tt
7 a a,
ane oe em
ae wot A> ye
: - i ov oe = erg are
by ‘eiet

a
oc.
ale
ry

Oe
ha

. yl ee A
— we > a rd Sly oe |
@., 42 Ot. 5 Dane Sim tat ey
are, : —' aa
‘. Res
Sera eee Soe
€ Sls amore
i pa PL
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a ae jaget See '>
ie > Woe
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47 ear
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lentil}

PLATE XII.

The nerves dissected from the animal and enlarged.

. Cerebral ganglia.
. Commissural cord connect-

ing cerebral ganglia.

. Posterior ganglia.

Commissural cord connect-
ing the cerebral and pos
terior ganglia.

. Pedal ganglion.
. Commissural cord connect-

ing the pedal and cerebral
ganglia.

g.n. The nerve whose branches
supply the gills.

b.n. The nerves of that part of
the mantle constituting
the inhalent and exhalent
siphons.

.m. n. Anterior mantle nerve.
p.- m. n. Posterior mantle nerve.
au. s. Auditory sac.
a. a.n. Anterior adductor nerve.
p. h.n. Peripheral nerve.

INTOUOTOUN IVA, TFICOVVIAUTIILICS .

State Mns Nat Hist 35. Ses

pei Nse lade WeedParsons & Co Albany, NY

PLATE XII

Fic. 1.— Enlargement of the posterior ganglia.
Fic. 2.— Enlargement of the cerebral ganglion.
Fic. 3.— Enlargement of the pedal ganglion.
Fic. 4.—The young of anodon taken from the gill.
Fic. 5.— The labial palpi held open and at right angles to the body, showing
their inner surfaces.
1. p. Labial palpi. m. Mouth.
Fic. 6.— One of the labial palpi. 7
Fie. 7 —Two of the ridges on the labial palpi enlarged, showing cilia.
Fic. 8.— Enlargement of interior of a palpus.
Fic. 9.— Enlargement of exterior of a palpus.

Plate 13.

State Mus Nat.Mist3

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