Charles Wesley Hargitt.

Outlines of general biology ; an introductory laboratory manual online

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posterior portion the metapodium, and between these two
is the mesopodium. Are these regions sharply marked off?

2. Head. At the anterior end note the position and form
of the mouth. Tentacles are present in this region. How
many? Size and form? Touch one with a needle. What
happens? On the tentacles are small, pigmented, glisten-
ing spots, the eyes. Note their position and number.

Locate the anal opening on the right side of the head. In
the air-breathing snails the respiratory opening is near the
anal opening.

3. Shell. Is there a division into valves? How many
turns does the shell make? Do the shells vary in size?
Do the coils turn to the right, or to the left? Is the coiling
loose or close, flat or conical? The apex of the shell is the
oldest part, the opening of the shell is the newest part of the
shell. In some species one side of the mouth of the shell
is drawn out into a spout-like process. For what purpose
is this? In some snails there is an oval plate which closes


the opening of the shell when the animal withdraws into
it. Is there such a plate, or operculum, in the form you are

The lines that run parallel to the mouth of the shell are
lines of growth. Are these uniformly spaced? Can you
explain any variations? The whorls or turns of the shell
run around a central axis, the columella. Observe the
columella and the spirals of the shell in a broken shell.
Describe the relations of the columella to the other parts
of the shell.

Make a drawing of the snail from the side, showing the
foot, head, shell.



WHILE the following directions have been made with
reference to the perch, the others named, or indeed almost
any species at hand may be employed. It will be especially
valuable to have a few living specimens, minnows or gold-
fish, in a laboratory aquarium for actual observations of

For dissection preserved specimens are quite as good as
those freshly killed or obtained from the market; the last
are likely to have been kept in storage for some time and
the internal organs are often worthless for study.*

I. General Features.

Note the shape of the body and its special differential
features head, tail, body proper, fins. Are the body
features sharply marked? How do they compare with
those of the frog? Is the shape adapted to the life and
habits of the fish? Note the scales, their shape and arrange-
ment. Are they found on all parts of the body? How are
they attached to the body? What is their relation to the
skin? Examine a few quite critically and decide whether
they are entirely naked and whether the margin is smooth
or toothed. A scale with a smooth, rounded outline is
called cycloid, one with a toothed margin is called ctenoid;
to which of these does your specimen belong?


U. External Anatomy.

1 . Fins. How many are there ? Where are they located ?
Are they alike? Fins are said to be paired or single. The
paired are called pectoral, occupying a position similar to
the fore legs of the frog, and ventral, situated back of the
pectorals and on the ventral side of the body. How many
unpaired fins? The one just behind the vent is known
as the anal, one occupying the median dorsal position is
the dorsal. What others are present and how characterized ?
Study especially the structure of the paired fins and com-
pare with the others. In what alike, in what different?
Study also the ray-like structure of the supporting rods
of the fins, are they alike in all?

2. Mouth. Note its shape and size. Open and close
the lower jaw and observe the movements of the several
parts. Are there lips? Identify the following bones of
the upper jaw: premaxillary, forming the anterior and lateral
portion and extending backward to unite with the maxillary.
Do both bear teeth? What is the shape of the teeth? The
lower jaw is composed of the dentary bones. Do they bear
teeth? Compare with those of the upper jaw. Within
the mouth cavity note the shape, size and position of the

3. The Eyes. Observe their location, size and shape.
Test the range of motion by pressing them with the forceps
or finger . Are there eyelids ?

4. Nostrils. How many openings? What is their shape
and position? Do the nostrils communicate with the
mouth as in the frog? Are they of use in breathing? How
do they operate in smelling?

5. Gill Openings. Observe that these openings are on
the side of the head and are covered by flaps, the opercles.


Can you identify the subopercle, preopercle, interopercle?
Under the opercles on the ventral side is the branchiostegal
membrane and the branchiostegal rays which support the
membrane. How many are there? Raise the operculum
and examine the gills, their number and arrangement and
method of support. On the anterior margin of the gill
arches are teeth called gill rakers. What function can you
suggest for them? Press down the tongue and observe
the effect upon gills and gill rakers. How does the fish
breathe? What motions are involved? Watch a fish in
the aquarium to find an answer to these questions.

6. Lateral Line. A series of raised, dot-like markings
along the sides of the body. Examine one of the scales
which has on it one of the dots and see what it is like. The
lateral line has a sensory function.

7. Openings. Just in front of the anal fin look for open-
ings of the anus and genital organs.

Make a drawing of the fish as seen from the side.

m. Internal Anatomy.

Make a median incision just in front of the anus and carry
it forward to the hinder border of the gills, being careful
not to injure the underlying organs. Make cuts at right
angles so that the flaps may be pressed to one side. Place
the fish on its side and work out the internal organs. Com-
pare the body cavity with that of the frog. Is there a
thoracic cavity distinct from an abdominal?

1. Liver. This is a reddish organ of considerable size.
How is it held in place? Is there more than a single lobe
in it? Is a gall-bladder present as in the frog?

2. Stomach. Raise the liver and push it to one side to
expose the stomach. From the stomach the esophagus


leads to the mouth, and extending posteriorly to the anus
is the intestine. What is the shape and size of the stomach?
Are there pyloric coeca present? (These are small finger-
shaped filaments, not present in all fish.) Note the mesen-
tery which supports the stomach and intestine.

3. Spleen. Observe its shape, color and position in the

4. Reproductive Organs. The size of these organs will
depend upon the season, i. e., whether it be before or after
the breeding period. At this season they are large and may
fill up most of the body cavity. The testes are usually
whitish organs occupying a position similar to that in the
frog. The ovaries may vary in color and are often bright
yellow or orange. Determine the openings of these organs
in the posterior part of the body cavity.

5. Kidney. Along the dorsal wall of the body cavity is
the large air bladder and just above are the tw r o kidneys.
The kidneys open into the urinary bladder in the posterior
part of the body, and this opens to the outside just back
of the anus.

6. Heart. The heart is in the extreme anterior part of
the body. Is it in the same cavity as the other organs?
What is the shape, and of how many chambers is it com-
posed? If it is desired to trace the bloodvessels they should
be injected as in the frog.

Make a drawing in side view to show the internal organs.

7. Nervous System. This system in the fish has much
in common with that of the frog. The brain and cord can
be more easily dissected in a specimen preserved in formalin.

8. Brain. Dissect off the skin and muscle and finally
the bony skull thus exposing the brain, and note: (a) the
cerebral hemispheres; (6) olfactory lobes; (<?) optic lobes;
(<f) thalamencephalon, between (a) and (c), upon which


note the pineal body; (e) cerebellum; (/) medulla oblongata,
from which continues the cord.

9. Nerves. The ten pairs of cranial nerves are very
similar to those of the frog and have the same names. The
spinal nerves may be exposed and their distribution studied
as may be directed by the instructor.

Make drawings to show the nervous system.


BOTH as a convenience in the study of organisms, and as
in some degree indicative of their genetic relationships,
various efforts have been made to arrange them under such a
systematic classification as would serve these ends. The work
involved in the foregoing laboratory course, while dealing
with a few typical organisms, and devoted chiefly to their
morphology and physiology, has also revealed unmistakable
relationships of structure and function, which in turn have
afforded evidence of the larger relationships of descent.
That a given kind or species of animals has descended from
a common line of ancestry is of course universally recognized.
That differing, but closely similar, species have likewise
descended from a common ancestor slightly more remote
is also generally recognized as a fact. Out of the study of
large series of such facts has come the conception of evolution,
long known to students of biology, but first brought into
prominence by Lamarck and Darwin. All modern sys-
tems of classification have been attempts to express the
facts of such relationships of descent or evolution. The
following partial and abbreviated tabulation of the animal
kingdom may illustrate, in a general way, the main features
of the subject.

PHYLUM PROTOZOA. Unicellular, microscopic animals,

or colonies of independent cells.

Class 1. Rhizopoda. Protozoa possessing the power
of thrusting out pseudopodia. A shell is often
present. Amoeba, Arcella, Heliozoa.


Class 2. Mastigophora. Protozoa, generally of small
size, provided with one or more flagella. Euglena,
Peranema, Pandorina, Volvox.

Class 3. Infusoria. Protozoa bearing cilia, with mouth
and contractile vacuole always present. Para-
mecium, Vorticella, Stentor, Colpoda.

Class 4. Sporozoa. Parasitic protozoa without motile
organs in the adult; reproduce by spore formation.

PHYLUM PORIFERA. Radially symmetrical animals, the
body wall containing many pores for the entrance
of water, and usually supported by a skeleton of

PHLYTJM CXELENTERATA. Radially symmetrical animals
with mouth and gastro-vascular cavity, but with-
out ccelom. Stinging cells present.

Class 1. Hydrozoa. Ccelenterates with solitary or
colonial polyps, and with an alternation of gen-
erations. The medusae have a velum. Hydra,
Pennaria, Obelia, Gonionemus.

Class 2. Scyphozoa. Ccelenterates of considerable size,
the medusa prominent but the polyps much re-
duced or absent. The edge of the bell is lobed and
a velum is not present. Aurelia, Cyanea.

Class 3. Actinozoa. Polyps solitary or colonial, with
esophageal tube and mesenteric folds. A medusa
generation is entirely lacking. Sea anemones and

PHYLUM ECHINODERMATA. Radially symmetrical ani-
mals usually with a pentamerous arrangement.
Mouth and anus present, ccelom well developed,
a water vascular system. The body wall con-
tains calcareous plates and usually bears spines.


Class 1. Asteroidea. Star-shaped forms, the arms not
sharply marked off from disc but with an am-
bulacral groove from which tube-feet project.

Class .2. Ophiuroidea. Star-shaped forms, the arms
sharply marked off from disc and without am-
bulacral groove. Brittle stars, serpent stars.

Class 3. Echinoidea. Spheroidal or discoidal forms with
a shell of closely fitting plates and with movable
spines. Tube feet project from five rows of pores
on the shell. Sea urchins.

Class 4. Holothuroidea. Elongated worm-like echino-
derms with muscular body wall containing scattered
plates. Contractile tentacles about the mouth,
and tube feet in the form of papillae. Sea cu-

PHYLUM PLATYHELMINTHES. Flattened, bilaterally sym-
metrical, worm-like animals with an excretory
system of branched canals containing flame cells.
Anus is not present, and coelom not developed.

Class 1. Turbellaria. Free living Platyhelminthes with
a ciliated ectoderm and a centrally located muscular,
protrusible proboscis. Planaria.

Class 2. Trematoda. Parasitic forms with unseg-
mented, flattened body. Anteriorly placed mouth
and one or more ventral suckers. Liver fluke.

Class 3. Cestoda. Elongated, and usually segmented,
Platyhelminthes without mouth or digestive tube.
Suckers or hooks at one end, and a complete re-
productive system in each mature segment. Tape

PHYLUM NEMATHELMINTHES. Elongated, cylindrical or
thread-like worms with unsegmented body. Ter-


minal mouth and anus, coelom present, appendages
wanting. Body covered with a heavy cuticle.
Free living or parasitic. Pork worm (Trichinella),
vinegar eel, thread worms,

PHYLUM ANNELIDA. Segmented worms, usually with a
well marked coelom. Internal organs segmentally
arranged. As a rule chitinous setae are embedded
in the skin.

Class 1. Chaetopoda. Annelida with conspicuous setae.
The well marked coelom divided by septa. Earth-
worm, Nereis.

Class 2. Hirudinea. Elongated, flattened annelida with
anterior and posterior suckers, without seise and
with median genital openings. Coelom much
reduced. Leeches.

Class 3. Gephyrsea. Unsegmented worm-like animals
with a spacious ccelom not divided by septa, an
anterior anus and a single pair of nephridia. Setae

PHYLUM MOLLUSCA. Bilaterally symmetrical, unseg-
mented animals, with a ventral foot, a mantle fold,
and usually a univalve or bivalve shell. The
central nervous system consists of a circum-eso-
phageal ring.

Class 1. Lamellibranchiata. Symmetrical mollusca with-
out head; with bilobed mantle, bivalve shell, and
usually with lamellate gills. Clams, mussels,

Class 2. Gastropoda. Asymmetrical mollusca with a
distinct head usually bearing tentacles, a muscular
creeping foot, a continuous mantle fold and usually
a coiled shell of one piece. Snails.


Class 3. Cephalopoda. Mollusca with a well marked
head, a circle of arms bearing suckers around the
mouth, and well developed eyes. There is a heavy
muscular mantle fold; the nervous system is con-
centrated in the head. Squid, octopus.
PHYLUM ARTHROPODA. Segmented animals with a
firm external skeleton and jointed appendages.

Class 1. Crustacea. Aquatic arthropods breathing by
means of gills, with two pairs of antennae and
.numerous pairs of biramous appendages on thorax
and abdomen. Crayfish, lobster, crab, water flea,

Class 2. Myriapoda. Worm-like arthropods with numer-
ous similar segments bearing similar appendages.
One pair of antennae, breathe by means of tracheae.
Millipeds, centipedes.

Class 3. Insecta. Arthropoda with the adults usually
bearing three pairs of legs and two pairs of wings;
body divided into head, thorax and abdomen;
single pair of antennas; breathe by tracheae. A
metamorphosis is common in the life history. Fly,
mosquito, beetle, grasshopper, bee.

Class 4. Arachnida. Arthropoda without antennae, with
four pairs of legs and two pairs of mouth parts.
Body divided into cephalothorax and abdomen.
Breathe by means of trachea? and book lungs.
Spiders, mites, scorpions.

PHYLUM VERTEBRATA. Animals with dorsal brain and
cord, enclosed in an unsegmented skull and a seg-
mented vertebral column. Red blood; usually
with two pairs of appendages.

Class 1. Pisces. Aquatic vertebrates breathing by
means of gills; typically with two paired and other
unpaired fins. Fishes.


Class 2. Amphibia. Cold blooded vertebrates with
naked scaleless skin. Breathe by lungs in adult
life commonly, the larvse breathe by gills. Heart
with two auricles and a single ventricle. Frogs,
toads, salamanders.

Class 3. Reptilia. Cold blooded scaly vertebrates.
Breathe by lungs; heart with auricles and two
imperfectly separated ventricles. Snakes, turtles,
alligators, lizards.

Class 4. Aves. Warm blooded, oviparous, bipedal
vertebrates covered with feathers. The chambers
of the heart are completely separated. The an-
terior appendages have the form of wings. Birds.

Class 5. Mammalia. Warm blooded, hairy vertebrates.
Viviparous; mammary glands with which they
suckle the young. Red blood corpuscles non-
nucleated. Mammals.



Collection and Preparation of Material.

Amoeba. While amoeba has a wide distribution, -in no
place is it very abundant, nor are culture methods as success-
ful as with other protozoa. By putting Elodea, Cerato-
phyllum, or other water plants, into a shallow dish with a
small amount of water and allowing the plants to decay,
amoebae may often be found in some abundance in the slimy
sediment. The slime on lily pads often contains amoebae.
Occasionally amoebae will be extremely abundant in the
scum on a freshly started hay infusion, especially when
pond weeds have been present in the infusion.

Par amecium. Into a hay infusion twenty-four hours old
(that made from dry timothy hay is best), place some water
and organic matter from almost any pond or swamp. After
about a week Paramecium will be found in abundance. Or
fill a jar half full of Elodea or other pond weeds, cover with
water and allow the plants to decay. Do not place the
jars in the direct sunlight.

To keep a culture in vigorous condition remove some of
the old hay and about one-third of the water, and add fresh
hay and water, every two or three days. If several cultures
are running and are changed on different days one may have
vigorous cultures of Paramecium constantly.

Conjugating paramecia are often obtained a few days or
a week after a fresh culture is started, if the culture has been
started by bringing in Paramecium from outside.


Paramecium probably never encysts and a hay infusion
made as sometimes directed, but not inoculated from some
source containing the animals, will not give rise to para-
mecia. The culture must be inoculated from an old culture,
or the animals must be introduced from outside sources.

To kill Paramecium hot Worcester's fluid is probably the
best. A round bottomed vial is filled one-third full from a
good culture, with as many of the animals and as little fluid
as possible. Fill the vial to the top with hot Worcester's
fluid and allow to stand fifteen minutes, during which time
the animals will settle to the bottom. With a pipette draw
off as much of the killing fluid as possible and add water to
wash, using several changes and stirring up the mass of
paramecia as little as possible. Stain in hematoxylin
rather heavily, destain with weak acid, or acid alcohol, until
the color is very faint except in the nucleus. W T ash in water,
dehydrate, clear and mount on a slide in balsam. Support
the cover glass to prevent crushing the animals.

Vorticella. If sticks, leaves, and pond weeds are placed
in a jar and allowed to stand a day or two a scum will form
on the water, and in this scum Vorticella will often be abun-
dant. In such fresh cultures large specimens are usually
found. The methods used for continuing Paramecium
cultures will be fairly successful for Vorticella. Similar
metiiods of killing and staining may be used but are not
very successful, on account of the contraction which usually
takes place in Vorticella.

Hydra. In ponds, swamps, and slow moving streams
covered with "duck-weed'"' (Lemna) green hydra will often
be abundant in spring and summer. Brown hydra is more
often found in larger ponds and lakes on Sagittaria and pond-
lily leaves. Place the plants, in both cases, in jars and set
in a bright place, but not in the direct sunlight. Within a


few days hydra, if present, will be found on the side of the
jar toward the light. In the autumn secure leaves from
the bottom of the pond and some of the surface mud.

Hydra will nourish if the jar is kept supplied with an
abundance of "water-fleas," Daphnia, Cyclops, Cypris,
etc., and budding will be abundant on the hydras. If the
food supply is allowed to diminish reproductive organs will
often begin to appear.

To kill hydra expanded remove a single specimen from
the aquarium with a pipette and place in a perfectly clean
watch glass with only a small amount of water. When the
animal in the watch glass is well expanded dash hot Wor-
cester's fluid, or hot Bouin's fluid, over it and allow to stand
ten minutes. The animal may then be washed and treated
for further use by staining or embedding for sections. Handle
very carefully since the killing fluid makes them rather brittle.
If whole mounts are desired a light stain with hematoxylin
is good. When mounting support the cover glass to pre-
vent crushing.

Hydroids, Jelly-fish. If these are collected the jelly-fish
should be preserved in formalin. Obelia should be nar-
cotized with magnesium sulphate before killing, to get the
hydranths expanded. It is well to have the hydroids killed
in some killing fluid and preserved in alcohol, though for
general external study preservation in formalin is satis-
factory. To make whole mounts of the hydroids proceed
as for hydra.

Earthworm. In the spring and early summer after a
soaking rain large earthworms can easily be obtained at
night. With a light examine the ground, preferably in a
garden or where there is little grass. Place the worms in
a can with a little soil until morning.

To preserve put the worms in a dish or pan with enough


water to just cover them and add a few drops of alcohol
every few minutes. After several hours they will be found
to be motionless and should not respond to tactile stimuli.
They should now be laid out straight and flat in a disk of
weak alcohol and allowed to remain for not more than four
hours. They are then to be placed in 80 per cent alcohol,
or better a mixture of alcohol and 10 per cent formalin for
preservation. The worms should be kept straight in the
preservative since they are much easier to study when in
this condition.

A somewhat clearer demonstration of setae and of external
openings can be made on worms killed (after narcotizing)
in 1 per cent chromic acid. After twenty-four hours in the
chromic acid, wash overnight in water and preserve in
alcohol. These are not so good for internal study.

For sectioning place worms in a dish with moist filter
paper and leave for several days until they void clean filter
paper instead of dirt. The digestive tract is now in con-
dition for sectioning. Narcotize with alcohol (or chloral
hydrate, or chloretone) and when motionless cut into small
pieces and fix in Bouin's fluid.

It is very easy to keep earthworms alive all winter with
little or no trouble. In a wooden box filled with moist
loamy soil place a number of worms and keep the box in
a cool place. Every few days leaves, pieces of apple, etc.,
should be spread on the surface for the worms to feed upon.
Cover the box with a heavy cloth (burlap) which is kept
moist and the soil will need very little attention. If the
soil should appear dry it must be sprinkled enough to
thoroughly moisten it.

Grasshopper. The larger grasshoppers are best for study
on account of their size, and are necessary if much internal
study is to be made. But for the study of external features


the small red-legged locust (Melanoplus femur-ntbrum)
will be satisfactory. Some of these should be alive in the
laboratory for study of the habits of living specimens.
Preserve insects in alcohol, rather than formalin.

Crayfish. Crayfish may be purchased alive from dealers,
or collected. If they are collected in the autumn and placed
in a tank (or tub) with water and kept in a cool, rather dark
place, they will live for a long time. If running water is
not available the water in the tank should be changed
occasionally, especially if a scum appears on it.

For demonstrating water currents over the gills use
powdered carmine, India-ink, methylene blue, etc., and
drop along the edge of the carapace. A piece of the carapace
at the side of the mouth parts may be removed in the living
animal* if carefully done, and the movement of the gill
bailer demonstrated.

The heart and larger bloodvessels are easily injected with
a thin starch mass. Either remove a piece of the carapace
and with syringe gently inject the mass into the heart, or

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Online LibraryCharles Wesley HargittOutlines of general biology ; an introductory laboratory manual → online text (page 8 of 10)