sternal angle (that between the two sides of the body of the sternum,)
is sharp and considerable. The costal processes are strong, while the
coracoid grooves are .25 in width. The manubrium is particularly
large and is bifid. Each of the six ribs, as well as the last cervi-
cal rib, has a well developed uncinate process.
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12 BULLETIN OF THE LABORATORIES
The Strongest bone in the shoulder girdle is the coracoid, which
is expanded below and obliquely winged for a short distance, then
is cylindrical and then curves inward, throwing off a flange-like
process where the scapula is articulated, and ends in an articular
surface against which the flattened upper part of the clavicle is
pressed. From the lower angle of this surface a strong tendon
passes to the process of the manubrium on that side. The clavicles
are of the usual form, forming the merry-thought in connection with
the anchylosed interclavicle. The scapula is united to both clavicle
and coracoid and with the latter furnishes a glenoid surface for the
humerus. Between these three bones, at their union, is a cavity, fora-
men triosseum, permitting the passage of the tendon of the sub-cla-
vius muscle.
The anterior extremity is of moderate size. The humerus is .95
long and is much expanded proximally where it is .33 in breadth.
The radial crest is short and quite prominent. The ulnar tuberosity
is very large and outwardly presents a large triangular surface and
within excludes two extensive fossae, divided by a strong septum, from
the end of which a strong process is developed. The opposite or
distal end of the humerus is less highly developed, but still shows a
high degree of perfection of the spinous appendages. The trochlea,
consisting of the radial and ulnar tubercles, are about as usual. The
radial condyle is a small prominence directed forward at the base of
the radius, while the ulnar condyle is a larger acute process, epctending
in the opposite direction. The radius^ the smaller bone of the arm,
is but slightly curved and measures 1.20 in length. The ulna curves
considerably, proximally, so that the sigmoid cavity is quite oblique to
the shaft, and the olecranon process is small and styloid. The carpus
contains two bones which have the usual positions. The ulnare is
applied to the back side of the ulna and rotates upon its smooth articu-
lar surface. The radiate caps the ulnar and is overlapped by the ra-
dius in front. The three metacarpals are fused at the base. The
first one can not be distinguished and its phalanx measures but .20.
The second metacarpal is . 65 long and is fused at both ends with the
slender third metacarpal. The second digit consists of two phalanges,
the first of which is .30 long and consists of two bars connected by a
thin plate of bone, the second being a triangular plate .15 long. The
third digit consists of a styloid phalanx .20 long. (The two ossicles
described by Schufeldt, in certain birds, as the cuneiform and the pen-
tosteon, are not discoverable in any of the skeleta before me.
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T\it pelvis is papery and yet very complete. The obturator fissure,
separating the ischium Sind/>u6ic moiety of the pelvis is divided into an
elongated posterior and smaller circular anterior foramen. The ilio-
siatic foramen is quadrate, with rounded angles. The pubic bone is
produced into a slender curved process, as usual in this group. The
femur is .91 long and nearly straight and requires no description.
The filfia is a symmetrical straight bone, 1.30 long, while the fibula
is nearly free from it and is about half its length. In the skeleta of
adult birds, such as those before us, it is useless to attempt to distin-
guish the tarsal bones which unite with its epiphyses, thus forming the
tibio-tarsus, nor yet the composition of the succeeding segment of the
leg, the tarso-metatarsus. The latter is .80 long and is furnished with
a strong process (** calcaneal,") behind, which is at present causing so
much discussion. The subdivision at the distal extremity into the
four metatarsals is distinct. The first of these, the hallux^ is provided
with a separate matatarsal, the accessorius, which is quite large and de-
scends to the level of the other united metatarsals. The phalanges
of the hallux are two in number, the first being very large, .32 long.
The claw borne by the following phalanx is the strongest on the foot.
The second toe has three phalanges, the third, four, and the shorter
fourth, five, as is the case in all of the present group of birds.
Such a bare description as is above given of points in the osteology
of a species of bird, is of little value, except as furnishing a basis for
comparison with others of its own and other groups. Such a com-
parative study we cannot at present attempt, but may, perhaps, profit-
ably note some points of difference between the present species and
others of its own family, Fringillidae. Quite at the other extreme
of the family may be found the genus Pipih, which is represented in
our region by the Chewink or Ground Robin, P, erythropthalmus,
a bird of singular appearance, in some points resembling the Orioles,
while mimicking the habits of the Brown Thrush. A comparison with
this species then may be expected to give us the limit of divergence in
structure within the family, and those points which are identical in
both may, with some probability, be assumed to be of family, ordinal
or class "rank.
The skull is of very different form, but the differences are
chiefly those accompanying the reduction in the size of the beak,
which in the Chewink is slender, almost Icterine. This slender point-
ed beak does not extend backward so far as in the true Finches, but
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14 BULLETIN OF THE LABORATORIES
the malar pillar is much longer and the angle of the beak and
the end of the tomia are forward from the orbit. The opening of the
nares is much larger and the lachrymo-nasal space is a very large tri-
angular opening. On this account the ascending process of the max-
illary is quite slender. As seen from above, the skull of Pipilo is
much narrower between the orbits and the facial portion of the skull
is easily distinguished from the cranial. The orbits are rather larger
and not nearly as well guarded. The lachrymal is of the same shape,
but lacks the long slender process directed backward, below. The
lachrymo-nasal foramen is small. The interorbital septum is very
poorly developed, two oblong foramina extending longitudinally leave
but a narrow bridge between them. The ethmoid is therefore greatly
reduced. The back of the skull is alike in both, but the opening of
the bullae is directed more forward. The palatal bones are quite sim-
ilar, but the posterior processes are not bifid. Two curved slender
rods, which seem at least partially ossified, pass from the palatal pro-
cesses of the maxillary to that part of the palatals farthest forward and
highest. The pterygoids are of the usual shape and are flattened an-
teriorly to slide over the sphenoids. The quadrate is smaller and of
the same form, but has a rather longer orbital process, proportionally.
The quadrato-jugal has the same hamular process posteriorly as described
in the Grosbeak. The lower jaw is, like the upper, rather weak.
The various parts entering into each ramus are indicated by the pres-
ence of a large oval foramen separating the surangular, angular and
splenial, and the flange of the articular is large. The differences in
the shoulder and arm are slight and are such as might occur in species
of the same genus. The sacrum is relatively much stronger and the
spinous armature is greater, this corresponding to the greater demand
upon the muscles there finding origin. The foramina are of the same
number, but the lower one is more elongated to correspond to the
greater development of the pubic bone. The femur is of ordinary
form, but the tibiotarsal segment is greatly enlarged. The fibula is
quite well developed and is anchylosed with the tibia about one half
an inch from the head, for a short distance, but is free above and be-
low. The head of the tibia develops two huge processes and there
is a small patella. The condyles are very large. The ^^ calcaneal '^
process, strangely enough, is very small and poorly ossified. The
foot itself is not particularly enlarged.
The form of the sternum is very closely alike in these birds ; in
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fact, the sternum is a valuable osteological index, for, not only is it
pretty constant in a given family, but it presents points of constant
difference between many families. The manubrium is larger, if any-
thing, than in the Grosbeak.
Such are some of the differences noted between these species and
they may be taken as indications of those points in the osseous struc-
ture most readily responding to changes in habit or habitation as in-
duced by changes in the environment. It is by the elimination of
the variable elements of different degrees of constancy that classifica-
tion can be placed upon a permanent and correct basis. The vari-
able points may be employed in distinguishing species, genera, etc., in
accordance with their relative permanence or value.
Plate I. Anatomy of Hesperiphona.
Fig. 1. Lateral view of entire skeleton.
Fig. 2. Skull seen from below. Q/\ quadratojugal ; /Y, palatal ; //, ptery-
goid ; spf sphenoid ; e, condyle ; Fm, foramen magnum ; Z, internal .flange of
mandible.
■^'^' 3* Transverse section of skull. F, vomer ; Q, quadrate bone ; Off
optic foramen ; other references as above. 3^, diagram of bones of skull.
^'^' 4 Quadrate bone and articulations. /V, pterygoid ; Q/\ quadratoju-
gal ; rt, accessory ossicles ; m c, sheath of Meckel's cartilage.
F^. 5. Hyoid arch.
F^. 6. Superior surface of a cervical vertebra.
F^. 7. Humerus.
F^. 8. A dorsal vertebra, from behind.
F^. 9. Muscles of the wing seen from above.
Fig. gA. Anterior part of wing from below.
Fig. 10. Skull denuded of skin and showing certain cervical muscles.
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II.
METAMORPHOSIS AND MORPHOLOGY OF CERTAIN
PHYLLOPOD CRUSTACEA.
[Plates V— VIII and Plate X.]
The group Phyllopoda is one of the most remarkable among crusta-
ceans, on account of the peculiar form and life history of most of its
members. About the animals of this group there clings a certain air
of mystery which may lead one to regard them as almost ** uncanny.'*
A pool by the wayside is suddenly formed by a shower and almost in-
stantly becomes populated with a swarm of animal life, which no one
ever saw there before and for the like of which we might search an
hundred miles in vain. In a few days the little tragedy is played and
the uncouth actors have disappeared, no one knows whither, having
sown the clay at the bottom of the now dry pool, with eggs which,
under favorable circumstances, may again put the play on the boards,
but only after being themselves thoroughly dried by the sun. In
short, in the study of these animals the unexpected is always appear-
ing and known laws, or at least theories, are again and again negatived.
We calmly institute a species when, lo ! the change in certain condi-
tions attending the development occasions the change to an entirely
different genus in our system.
(See V. Siebold, in Sitzungsberickte d. math.phys. Classe zu Muenchen^ 1S73, ^^^
the paper by Schmankewitsch in the Zeitschrift fuer Wissenchaftliche Zoologie^ XXV
Suppl., 1875.)
In spite of many able papers and works on American Phyllopods
(notably the monograph, by Prof. Packard, in The Geol. Surv, Terr.,
i2>62>y Part ly Sec. 2.) many points of deepest interest remain to be
cleared up, and particularly such as relate to the development history
and homologies of organs. In the present paper a few observations
made some years ago, are presented with no attempt to discuss their
bearing upon the questions in dispute. The student conversant with
the literature of this subject will observe, however, that these facts
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make necessary a modification of views at present in vogue in several
important particulars. The work was arbitrarily closed by circum-
stances and the material was long suppressed, in the hope of continu-
ing a study which proved of absorbing interest ; but, as this hope is
now extinct and no motive remains for further delay, the observations
are presented in their necessarily fragmentary form, hoping to fill a
place in the life-history of these remarkable animals.
The Phyllopoda are extremely well adapted for use in biological
laboratories and the outline here given may make the process of de-
velopment plainer to the student who is fortunate enough to be sup-
plied with such material for study. The two animals described may
be found in early spring and late summer, in many temporary pools
throughout the eastern zoographical province of North America.
A. Larval Development of Limnetis gouldii, Bd,
Limnetis is a genus of the Family Limnadiad^ of Baird, which
includes crustaceans enclosed in a bivalved shell, within which is con-
cealed a body like that of a Water Flea, but having ten to twenty-
seven pairs of leaf-like swimming feet. The very large head projects
from between the valves in front and is flanked on either side by a
biramose second antenna, while the first pair of antennae is very small.
A figure of the adult of the present species will be found in the mono-
graph by Dr. Packard, and also in a paper by the present writer, in the
loth Annual of the Minnesota Geological Survey.
The earliest stage seen (Plate VI, Fig. 2.) was the simple nauplius-
form common to all this group of Crustacea, but so curiously modified
as to at first almost defy recognition. The animal, as viewed from
above, seems covered almost entirely by an oval shield, which is thickly
studded with spines arranged in anastomosing lines. The head ex-
tends into a frontal prominence, which is densely bearded. The pos-
terior part of the body forms a blunt prominence, bearing two spines.
The eye, occupying the front of the head, consists of a single pig>
ment fleck, with at first a single lense (?). The digestive tract is
simple and similar to that of other Phyllopod larvae. In the protu-
berance which represents the future abdomen, the muscles producing
the pumping action of the rectum are well developed and anal respi-
ration at once begins.
The appendages differ only in form from those of other larvae.
The antennules are long and curved prolongations of the frontal region
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l8 BULLETIN OF THE LABORATORIES
and project laterally. They are covered with a spiny cuticle, like
the antennules of the nauplius of Chirac ephalus^ but are less movable
and less obviously tactile organs. It has been denied that these are
really antennae, but the history of their further development makes it
clear that they are really representatives of those organs, though ob-
scured by their covering.
Although the nauplius of Limnetes is said by authors (Packard,
Monogr. Phyllopod Crust, etc.) to be distinguished from other nauplii
by the small size of the labrum, this is founded upon a mistake. The
labrum is really the most prominent of the larval organs. It is,
indeed, of monstrous form and is so enlarged as to become a valve
nearly as large as the shield-like expansion of the body above. The
larva resembles a small turtle, from the edge of whose shell protrude
two pairs of appendages.
The labrum is thorned, as is the whole body, and is slightly, if at
all, movable. In this respect it differs little from other young nauplii.
Like the first pair of antennae, the labrum is obscured by its larval
envelope, similar to that which extends the carapace of the body to
form a false shell. The second antennae are of the usual form among
Phyllopods, the anterior branch being five-, the lower one two-jointed.
The basal portion is furnished with a prominence bearing two heavy
claws. The palp of the mandible is of the usual form.
In the next stages slow changes accompany the increase in size-
A dorsal area is marked off over the maxillary and mandiblar seg-
ments, from which the shell develops under the larval covering. The
nauplius eye becomes associated with a pair of club-shaped sensory
hairs. A ventral swelling becomes distinct and proceeds to segment
itself and elaborate limbs. (Fig. i, Plate VII.) In figure ii of this
plate, which gives a semi-diagramatic under view of the abdomen, is
shown that, as in other Phyllopods, the appendiculate segments seem
to appear at once and the development goes on then from before back-
ward. Prior to the appearance of feet (stage of Fig. i.) the animal
is about 0.33 mm. long, but becomes over 0.50 mm., before the meta-
morphosis. In the last stage prior to assuming the characteristics of
the adult, the antennules seem smaller, the labrum has become cordate
and very wide, while a prominence appears below the eye. Rudi-
ments of the compound eye are visible and the sensory filaments over-
lying the pigment fleck are developed. The anterior part of the
digestive tract has bifurcated and its branches extend toward the labrum.
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The accessory branch of the second antenna, with its forceps, has be-
come large. Now the hypodermic contents of the antennules with-
draw from its shell apd compact themselves into the mature form, de-
veloping, at the same time, sensory rods in their substance. The con-
tents of the labrum fall away from the walls and gather into a lobe-like
body. Feet have formed, and a single-chambered heart is actively
pulsating. The future shell may now be seen under the larval cover-
ing, connected only with the back over the segments bearing gnathites,
and hanging free about the edges. When the moult is affected the
labrum falls within the valves, carrying with it the small tactile anten-
nules, which hang pendant by a slender stalk. The frontal promi-
nence, however, is elongated, forming the beak. The larva is now a
diminutive of the adult. In its future development the form elongates
and finally again becomes rounded and assumes the familiar appear-
ance. The branches from the stomach fill the front of the head with
so-called liver-lobes. The compound eye becomes perfected, while
the nauplius eye is covered by filaments charged with some unknown
sensory function. Jhe heart becomes multi-chambered and the geni-
tal organs appear. For a figure of a young Limnetes, see Types of
Animal Life^ etc., by the author ; for figures of the adult and a discus-
sion of relationships, see Packard's *' Monograph of the Phyllopod
Crustacea of America " ; U, S. Geol, Surv, of Terr. 1878, Part I.
Farther details may be gathered from the plates. It is a matter of
regret that Grube's work on the development of the European Lim-
netes brachyura was not accessable to me during the period which was
covered by this paper. My recollection is, however, that the pro-
eesses are, in the main, identical, hut that Grube fails to identify all
the organs of the embryo.
B. Post-embryonic Development of Chirocephalus.
The species studied is assumed to be the common C. holmani, Ryder,
although the oldest male seen differed in several particular from the
description of that species. One must imagine a fish-like, transparent
animal, about one-half inch long, balancing itself in the water by the
movement of eleven pairs of lamellate swimming feet. The colors
are brilliant and do not interfere with an almost perfect transparency of
the body.
The earliest stage seen is that figured on Plate V, Fig. i. The
animal is at that period .93 mm. long and the antennae measure about
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20 BULLETIN OF THE LABORATORIES
.57 mm., the antennules .32 mm. The form is that of a nauplius
toward the end of its first phase. The antennules are much like
those of males of Mbina, being curved abruptly near the middle.
They are clothed with a spiny larval integument, which disappears in
the next stage. The sensory ganglia in the end and the connecting
nerves are present; of the latter there seem to be two bundles having
a different course. The larval eye in the middle of the head is dis-
tinct and has two lenses, or, rather, crystalline bodies.
The antennae are of the form usual to larvae of this family, the
rami being unequal, the shorter being very indistinctly two-jointed, the
longer eigh teen-jointed. Near the base a small prominence bears long
spines, later to serve a temporary purpose in bringing food to the
mouth. The mandiblar palp is indistinctly 6-jointed, the inner ramus
of this limb, or mandible proper, has a single spine.
The thoracic segments are already indicated and rudimentary limbs
lie under the larval skin. The abdomen bears two styles, and has a
set of muscles adapted to produce anal respiration in the rectum. The
stomach is simple and glandular. Although no heart could be distin-
guished, blood corpuscles crowd the antennae and other parts of the
body, (see figure 4.) Rudiments of the compound eyes are seen on
the sides of the head where pigment is collected.
In the next stage the animal may be .98 mm. long (Fig. 2.) and
several changes appear. A well marked scutum covers the mandib-
lar and maxillary segments. The/ antennules have losl their spiny
covering and the proportions of the antennae have changed. At the
base of the antennae certain organs develop, which present great re-
semblances to the branchial saCs of the other feet, but which become
the shell-glands of the adult. This is parallel to the like origin of
these organs in copepods, as we have demonstrated in Diaptomus. In
Limnetes it was impossible to follow the development of the shell-
gland. (See figure 6, 0, shell gland ; M, mouth; Z, labrum ; Md,
mandible; Mx, maxilla; Mx 2, second maxilla.) The brain lobes
or supra-cesophagal ganglia resemble those organs in cladocera, the
optic-lobes being apparently hollow, however. The posterior part of
the body is now considerably elongated. The segments of the thorax
seem to be all differentiated at once and the segmentation is obscured
by a false segmenting of the posterior part of that region or the appa-
rent absence of segments. The region about the rectum is open and
crossed by the muscles giving it motion. It frequently seemed to me
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that this chamber was that in which the blood-corpuscles (or, better,
lymph- cells) were formed. The rectum is covered with irregular
masses of cells of varying size, and I more than once thought to have
observed their change to lymph-cells. It was impossible, unfortu-
nately, in the time allotted to observe the development of the circu-
latory system, but it would seem that the heart differentiates from the
connective tissues between the stomach and the scutum.
(Fig. 3 illustrates not only the formation of the posterior appendic-
ular segments, but the rectal sinus with its muscles and lymph-cells.
A simple valvular apparatus separates the rectum from the anterior part
of the digestive tract. )
The next stage is illustrated on Plate VI, Fig. i. A change in
proportion and in size is all that requires notice. Figures 3-6, illus-
trate the growth of the appendages. Fig. 3 is the first foot of the
right side of an individual over 1.5 mm. long. Fig. 4 is the same of
a younger individual of which Fig. 5 is the sixth and Fig. 6, the ninth
foot. Fig. 7 shows how the matrices of the caudal spines are devel-
oped from enlarged cells as are the corresponding parts in Daphnia.
Fig 2, of Plate VII, illustrates the general characters of the animal
when about 2 mm. long. The maxilla have become larger and the
feet begin to assume their definitive form.
Fig. 3 shows the growth of the caudal stylets and the character of
the valve at the opening of the anus, as well as the prolonged matrix
at the setae. Fig. 4 illustrates the differentiation of the optic lobes
and of the anterior part of the stomach. The heart is by this time
well formed and whatever part the rectal cells may have played in
originating lymph-cells, is lost. The liver lobes grow out from the
stomach and the labrum becomes reduced. The antennae now un-
dergo a rapid and remarkable transformation. In the male the shorter
ramus becomes atrophied as shown in Fig. 10, and from the base an
epipodal body is formed just as in the case of the feet. At first this
pouch resembles homologous organs in the feet, but soon it alters and